Category: ADU

Usually yes — but probably not the building you are picturing, and in Los Angeles the ADU route is almost always easier. Two things decide it. First, your zone: in the R1 one-family zone the backyard guest building may not be built on a lot smaller than 10,000 square feet, which rules out most ordinary Valley and South Bay lots. Second, the kitchen: a guest building may not have one. Put a kitchen in and it stops being a guest house and becomes a dwelling unit — which is exactly what an ADU is, and an ADU comes with protections a guest house does not.

Green Design and Build is a licensed general contractor (CSLB #1110975) based in Van Nuys, building ADUs and home additions across Los Angeles, Orange and Ventura counties and the western Inland Empire. Below is what the Los Angeles code actually says, the lot-size rule by zone, and how to decide which of the two routes fits your property.

“Guest house” means something specific in Los Angeles

This is where most articles on the subject go wrong. The Los Angeles Municipal Code defines three separate things, and the one homeowners mean is not the one called a guest house.

The small separate building in the backyard where a visiting relative sleeps is accessory living quarters. Three constraints come with that label, and all three surprise people:

• No kitchen facilities. Not a small one, not a hidden one.
• Temporary occupancy by guests of the people who live in the main house — it is not a place someone lives permanently.
• Not rented, and not used as a separate dwelling unit. There is no version of this that produces income.

The lot-size rule nobody mentions

Whether you may build accessory living quarters at all depends on your zone, and the thresholds are not the same across the residential zones. In the City of Los Angeles:

R1 is the zone most Los Angeles single-family neighborhoods sit in, and a typical R1 lot is nowhere near 10,000 square feet — a 50 by 135 foot lot is 6,750. So for a large share of homeowners asking this question, a permitted guest house in the backyard is simply not available, while an ADU on the same lot is guaranteed by state law. That single fact decides most of these projects.

You can look your own property up in minutes. The City of Los Angeles publishes ZIMAS, its zoning information map: enter the address and it returns the zone, the lot area, the overlays and the planning case history. Property outside the city limits is handled by that city’s own planning department.

Why the ADU route is usually easier

A guest house is a purely local use, permitted or not at the city’s discretion. An ADU is protected by state law, and the difference is not marginal.

Put plainly: for roughly the same construction, the ADU version is easier to get approved, can be larger, can be closer to the property line, houses a family member permanently, and can be rented later. The guest house version does none of that and is off the table entirely on most R1 lots. The only real argument for a guest house is that you specifically do not want a second dwelling unit on the title — worth discussing with your own adviser if that matters to you.

The kitchen trap

The most common plan we are asked to price is the worst one: permit a kitchen-less guest building now, add a kitchen quietly later. It does not work, for a simple reason. The moment cooking facilities appear, the building stops meeting the accessory living quarters definition and becomes an unpermitted dwelling unit. That is a code enforcement matter, it surfaces on sale and refinance, and it is far more expensive to unwind than doing it properly was.

It is also harder to hide than people expect. Los Angeles has long-standing interpretive guidance listing the features that indicate kitchen facilities — a gas outlet, a 220-volt outlet, a double sink, a bar sink over a square foot, space for a refrigerator over ten cubic feet, a disposal, space for a dishwasher, more than ten square feet of counter. That guidance is commentary rather than code text, and a plan checker applies judgment, but it tells you how carefully the line is policed. Our article on what an ADU is goes through that list in more detail.

If there is any chance you will want a kitchen one day, permit the building as an ADU from the start. It costs less than doing it twice and it is legal at every stage.

What each route costs

A detached kitchen-less building is not much cheaper than a detached ADU. You still pour a foundation, frame, roof, insulate, run water, sewer and power, and finish a bathroom. Leaving out the kitchen saves the cabinets, the appliances and some of the plumbing and electrical — a modest fraction of the total, in exchange for a building nobody may live in.

What if guests only come a few times a year?

Then the honest answer is often neither. Two alternatives serve most families better:

• A bedroom and bathroom suite inside the house, with its own entrance if you want it. The simplest permit of all three, and you get the space back the other fifty weekends a year. Our guide to building a mother-in-law suite covers how to design one that works for an aging parent as well as a weekend guest.
• An ADU you use however you like. Nothing obliges you to rent it. Guests stay in it when they visit, it is a home office the rest of the time, and the option to rent it on a lease longer than 30 days remains open for whenever circumstances change.

The second is what most of our clients choose once the numbers are in front of them. The flexibility is worth more than the saving.

Check your own property in twenty minutes

1. Look up your zone and lot area in ZIMAS if you are in the City of Los Angeles, or your city’s zoning map if you are not.
2. Compare the lot area against the threshold for your zone in the table above. Under it, the guest house question answers itself.
3. Check for overlays — hillside, coastal, historic preservation, specific plan. Each adds rules on top.
4. Measure what is left after four-foot side and rear setbacks, the driveway you still need, and any easement on your title report.
5. Read your city’s ADU ordinance. Our Los Angeles ADU rules by city page and ADU rules calculator are the quickest way in.

Guest house FAQs

Can I build a guest house on my property in Los Angeles?

Only if your zone allows it and your lot is large enough. In the R1 one-family zone, accessory living quarters may not be built on a lot smaller than 10,000 square feet; in the RE residential estate zone the threshold is 20,000 square feet. The RA suburban zone states no lot-area minimum; the RS suburban zone requires a lot of at least 15,000 square feet. Most standard R1 lots fall short, which is why an ADU is usually the workable route.

What is the difference between a guest house and an ADU?

A kitchen. An ADU has one and is an independent home; a guest building may not have one and is not a dwelling unit. The consequences follow from that: an ADU can be lived in permanently and rented on a lease longer than 30 days, is approved ministerially within 60 days, and carries guaranteed size and setback protections under state law. A guest house has none of those.

Can a guest house have a bathroom?

Yes. A bathroom does not make a building a dwelling unit — cooking facilities do. Accessory living quarters may have a bathroom, and normally should; what they may not have is a kitchen.

Can I rent out a guest house?

No. The definition explicitly excludes renting or using it as a separate dwelling unit. If rental income is any part of the plan, build an ADU instead — our page on ADU rental income in Los Angeles sets current rent benchmarks against build cost.

Can someone live in a guest house permanently?

No. Accessory living quarters are defined as the temporary dwelling of guests of the people occupying the main house. A relative moving in for good needs a dwelling unit, which means an ADU or a junior ADU.

Can I add a kitchen to my guest house later?

Not without a permit, and adding one converts the building into a dwelling unit. Done without permits it becomes an unpermitted unit, which is a code enforcement problem and a liability at sale or refinance. If a kitchen may ever be wanted, permit the building as an ADU from the outset.

How do I find out what zone my property is in?

In the City of Los Angeles, enter the address in ZIMAS, the city’s zoning information map, which returns the zone, lot area and any overlays. Outside the city, check with that city’s planning department.

Do these rules apply outside Los Angeles?

The guest house definitions and lot-size thresholds above are City of Los Angeles rules and apply only there. Every city writes its own. State ADU law is the part that applies everywhere in California, which is another reason the ADU route travels better across jurisdictions.

Find out what your lot allows

We will check your zone, lot area, setbacks, utilities and overlays, tell you whether a guest building is even available to you and what size ADU is realistic instead, and put a written budgeting range against it. Site visits take about two hours and a written proposal follows within 48 hours.

A granny flat is a small, self-contained home on the same lot as a house. In California it is permitted as an accessory dwelling unit; “granny flat” is everyday language and appears nowhere in state law. The useful question is not what to call it but what will actually fit behind your house — and state law answers a surprising amount of that for you. Every California city must allow a detached unit of at least 800 square feet with four-foot side and rear setbacks, and must approve or deny a complete application within 60 days.

Green Design and Build is a licensed general contractor (CSLB #1110975) based in Van Nuys. We design, permit and build ADUs across Los Angeles, Orange and Ventura counties and the western Inland Empire. This page is about feasibility: what the law guarantees you, what your lot decides, and how to check both before you spend money on drawings.

Is a granny flat a real category in California?

No — and that is good news. “Granny flat” is British and Australian in origin and arrived in California as shorthand for a small unit built for an aging parent. It has no definition in the Government Code and none in the Los Angeles Municipal Code, so nobody is going to refuse your permit over the word.

What your building department will decide is which of three things you are building:

• An ADU — a separate home with its own kitchen, bathroom and entrance, whether detached, attached, or converted from a garage.
• A junior ADU — up to 500 sq ft inside the walls of the existing house, with an efficiency kitchen and its own exterior door.
• An accessory structure — no kitchen, so nobody may live in it as an independent home.

Almost everyone who says “granny flat” means the first one. Our guide to what an ADU is and what all the other names mean covers the full vocabulary; this page is about whether one fits.

What state law guarantees you

California ADU law works by setting floors that no city ordinance may go below. These are the ones that decide feasibility on a small lot.

How small can a granny flat be?

Smaller than most people assume. California’s Health and Safety Code permits an efficiency unit with a minimum floor area of 150 square feet for up to two occupants, and state ADU law separately forbids a city from setting a minimum that would prohibit an efficiency unit. Underneath that sit the ordinary residential code minimums: a habitable room must be at least 70 square feet and at least 7 feet in any horizontal dimension, with ceilings at least 7 feet high — 6 feet 8 inches in a bathroom or laundry.

You will see 190 square feet quoted as the minimum on a great many contractor websites. That figure comes from the Building Code’s efficiency dwelling unit section (CBC 1208.4, reduced from 220 square feet in the 2022 code), not from ADU law. Build small deliberately if the lot demands it, but build it to the real numbers.

How to check your own lot in an afternoon

1. Get your lot dimensions. The county assessor’s parcel record gives you the lot size and shape. A rectangular lot makes this easy; a flag lot, a corner lot or a hillside lot rarely does.
2. Measure from the back of the house to the rear property line, and from the house to each side line. A tape measure and an hour is enough at this stage. Four feet of that belongs to the setback on the side and rear.
3. Subtract what is already spoken for. The driveway you still need, the sewer lateral, the main water line, the electrical service run, any protected tree and its root zone, and any easement across the back of the lot. Easements are the one that catches people, and they are on the title report you already have.
4. Read your own city’s ordinance, because the state floor is a floor. Our Los Angeles ADU rules by city page and the ADU rules calculator are the quickest way in for a specific address.

If what is left is a rectangle of roughly 20 by 30 feet, you have room for a comfortable one-bedroom. If it is narrower, a long, shallow plan along the rear fence often works better than trying to center a square building. If there is genuinely no room, a garage conversion or a junior ADU inside the house is usually the answer rather than the end of the idea — we compare them in detached ADU vs. garage conversion.

Pre-approved designs can shorten everything that follows. The city’s standard plan program offers vetted detached plans across a wide range of sizes; our page on ADU standard plans in Los Angeles explains how they work.

The 60-day clock, and what “deemed approved” means

This is the part of California ADU law homeowners most often do not know they have. Under Government Code section 66317, an ADU permit application is decided ministerially — no discretionary review, no hearing, no neighbors objecting at a public meeting. And the clock is real:

• The agency must decide whether your application is complete within the statutory period and, if it is not, give you a written list of what is missing and how to fix it. It may not later demand something that was not on that list.
• If it fails to make that completeness determination on time, the application is deemed complete.
• Once complete, the agency must approve or deny within 60 days where there is already a house on the lot.
• If it does neither within 60 days, the application is deemed approved.
• A denial has to come back in writing, within that same period, with a full set of comments.

Two practical consequences. First, a complete, well-prepared submittal is worth real money, because the clock only starts when the application is complete — most delay is caused at the front end, not by the city. Second, if you are being told informally that “it will take as long as it takes,” that is not what the statute says. Note that the 60 days is tolled if you request a delay, and runs differently when the ADU is submitted alongside an application for a brand-new house on the same lot.

Permit approval is not the whole schedule, of course — design, engineering and construction still take the time they take. Our page on how long an ADU takes to build sets out the realistic end-to-end picture, which is usually six months to a year.

What a granny flat costs in Los Angeles

The costs that catch people out are rarely the finishes. They are the electrical service upgrade an older house needs before it can carry a second unit, the sewer lateral if a camera finds it broken, the trenching distance from the house to the new building, and the site work on a sloped lot. Ask about all four before you compare two quotes — most of the variation between bids comes from here, as we explain in why ADU quotes vary so much. Financing routes are covered on our ADU financing options page.

Does a granny flat add value?

It adds a second legal dwelling and rentable square footage, and in Los Angeles County the rent a small unit commands is substantial — we put current HUD rent benchmarks against build cost on our ADU rental income page.

Resale value is a separate question, and anyone quoting you a confident percentage is guessing. What an ADU adds at sale depends on the appraisal, and appraisers in many neighborhoods still have few comparable sales of houses with permitted ADUs to work from. Two things you control do matter: the unit must be permitted and finalled, because an unpermitted conversion is a liability at sale rather than an asset, and the paperwork — permits, final inspection, plans — should be kept somewhere you can find it years later. Build it legally and document it, and you have an asset a buyer, a lender and an appraiser can all see.

Building new living space is also new construction for property tax purposes: the county assessor adds the assessed value of what you built to your existing assessment, and your original home is not reassessed.

Mistakes we see on small lots

• Designing before checking the easements. A utility easement across the rear of the lot can make the obvious location the one place you cannot build.
• Crossing 750 sq ft without meaning to. Going from 740 to 780 sq ft changes the impact fee position for forty square feet of floor.
• Ignoring the trench. Water, sewer and power have to reach the new building. A unit at the far back corner of a deep lot costs more than the same unit close to the house, before a single fixture is chosen.
• Assuming a converted garage has a usable slab. Garage slabs are often sloped to drain and frequently have no vapor barrier. Both are solvable; neither is free.
• Submitting an incomplete application. The 60-day clock starts when the application is complete, so an incomplete submittal costs you the thing the statute was meant to give you.
• Legalizing an old conversion the wrong way. A unit built without permits before 2020 follows a different path from converting a lawfully permitted structure today. Get it classified correctly first.

Granny flat FAQs

What is a granny flat?

A granny flat is a small self-contained home on the same lot as a main house, with its own kitchen, bathroom and entrance. The term is informal. In California the same building is permitted as an accessory dwelling unit, or as a junior accessory dwelling unit if it is built inside the walls of the existing house.

Are granny flats legal in California?

Yes. State law requires every city and county to allow accessory dwelling units on lots with an existing or proposed home, and applications are approved ministerially rather than through a hearing. Local ordinances add detail on top of the state minimums, but they cannot go below them.

How big can a granny flat be in California?

A city may not cap an ADU below 850 square feet, or below 1,000 square feet for a unit with more than one bedroom, and must allow at least 800 square feet with four-foot side and rear setbacks whatever its other development standards say. There is no statewide maximum. The 1,200 square feet quoted on most websites is the state default cap for a detached ADU where a city has no compliant ordinance (Gov. Code 66314(d)(5)); a city may set its own cap, higher or lower, but never below the 850 or 1,000 square foot floor.

How small can a granny flat be?

California allows an efficiency unit with a minimum floor area of 150 square feet for up to two occupants, and a city may not impose a minimum size that prohibits one. Residential code minimums still apply: habitable rooms of at least 70 square feet, at least 7 feet in any horizontal dimension, with 7-foot ceilings.

How close to the property line can I build?

State law requires cities to permit a detached ADU with four-foot side and rear setbacks. Front setbacks are set locally, and a city cannot use a front setback requirement to prevent an 800 square foot unit with four-foot side and rear setbacks from being built.

How long does the permit take?

Once your application is complete, the agency has 60 days to approve or deny it where a house already exists on the lot, and if it does neither the application is deemed approved. Getting to a complete application — design, engineering, the required documents — is the part that takes real time.

Can I rent out a granny flat?

Yes, on a lease longer than 30 days. State law lets a city require that minimum term, and cities may be stricter. An ADU cannot be sold separately from the main house on a single-family lot.

Do I need parking for a granny flat?

You are not required to replace parking lost when a garage is converted into an ADU. Parking requirements for new units are limited by state law and vary by location, particularly near transit, so check your city’s ordinance for your address.

Find out what fits on your lot

The fastest way to an answer is someone standing in your backyard with a tape measure and the ordinance for your city. We will check setbacks, utilities, access and slope, tell you what size unit is realistic at your address, and put a written budgeting range against it. Site visits take about two hours and a written proposal follows within 48 hours.

A casita is a small, separate living space on the same property as a main house. The word is Spanish for “little house,” and in Southern California it usually describes a detached backyard unit built in a Spanish or Mediterranean idiom to match the house in front of it. Legally, California does not recognize the word at all: if your casita has a kitchen it is an accessory dwelling unit (ADU) and is permitted as one; if it has no kitchen it is an accessory structure or a guest room. “Casita” describes the architecture. “ADU” describes the permit.

Green Design and Build is a licensed general contractor (CSLB #1110975) based in Van Nuys, designing and building ADUs across Los Angeles, Orange and Ventura counties and the western Inland Empire. This page covers what the word actually means, how a casita differs from a pool house or a guest house in the eyes of a plan checker, and how to design one that looks like it was always there.

Where the word comes from

Casita is the diminutive of casa. Across the American Southwest it has long meant a small secondary dwelling on a family property — the building a grown child, a grandparent or a ranch hand lived in. It carried no legal meaning then and it carries none now.

What gave the word its architectural flavor in California is the housing stock. Spanish Colonial Revival spread through the state after the 1915 Panama-California Exposition in San Diego, whose buildings were designed in that idiom by the architect Bertram Goodhue, and it became the default look for Southern California neighborhoods built through the 1920s and 1930s. Whole swathes of Los Angeles — Hancock Park, parts of the San Fernando Valley, Pasadena, the Westside — are full of white or cream stucco houses with low-pitched clay tile roofs, arched openings and wrought iron. A small stucco-and-tile building in the back of one of those lots is a casita. The same building in glass and black steel behind a mid-century ranch is just an ADU.

Real estate listings have blurred the term further. In a listing, “casita” may mean a detached ADU with a full kitchen, an attached guest suite with its own entrance, or a converted pool house with a bathroom and nothing else. Before you buy or build, find out which.

Casita, ADU, pool house, guest house: what actually differs

Only one distinction matters to a building department, and it is not the style. It is whether the building has permanent provisions for cooking. Under Government Code section 66313 a dwelling unit needs permanent provisions for living, sleeping, eating, cooking and sanitation; the Los Angeles Municipal Code defines a dwelling unit as a group of rooms, one of which is a kitchen. Everything below follows from that one line.

The practical consequence: a casita with a kitchen is the version worth building. It can be lived in year-round, it can be rented on a lease longer than 30 days, and it is what gives the square footage its value. A casita without a kitchen costs nearly as much to build and does far less. Our guide to what an ADU is, and what all the other names mean maps the full vocabulary.

Designing a casita that looks like it belongs

The failure mode is a beige box with a token arch. A casita reads as authentic when a handful of proportions are right, and no amount of decoration rescues it when they are wrong.

Roof pitch and tile

Spanish Colonial Revival roofs are low-pitched, with shallow or nonexistent eaves and clay barrel tile. Copy the pitch of the main house rather than the pitch that is cheapest to frame; a casita with a steeper roof than the house it sits behind will always look like an outbuilding. Two practical notes: clay and concrete tile weigh several times what composition shingles do, so the framing has to be engineered for the load — straightforward on a new detached unit, sometimes a reason to reinforce on a garage conversion — and California’s energy code has requirements for roof products, so confirm the specific tile you want is compliant before it is ordered.

Stucco texture and color

Match the texture of the main house first and the color second. A sand or light-lace finish beside a 1920s house with hand-troweled stucco is the single most common giveaway. Colors in this idiom run warm and pale — white, cream, buff, a dusty ochre — and the trim is typically the darker element, not the wall. If the main house has been repainted in something un-period, decide deliberately whether the casita follows the house or the neighborhood.

Openings

Windows in this style are tall and narrow rather than wide, often in pairs, often divided into small panes, and set deep in the wall so the reveal throws a shadow. That depth is where cheap construction gives itself away: a window flush with the stucco reads as modern no matter what shape it is. Arches should be used sparingly and at the entry rather than everywhere. French doors onto a patio are period-correct and do more for daily life than any decorative feature.

The outdoor room

Historically these houses were organized around a courtyard. You will rarely have room for one behind an existing Los Angeles house, but the principle transfers: give the casita a small paved area of its own, screened from the main house by planting rather than fence, with shade. A covered patio or a simple pergola outside the French doors adds more perceived space than the same money spent on interior square footage. Our outdoor living pages cover patio covers, pergolas and paving.

Details, in moderation

Wrought iron on one window, a tiled riser on one step, a single decorative vent. The original houses were modest; the revival versions people admire are restrained. Saltillo or terracotta-look tile inside, plaster rather than heavy texture, exposed beams only if the ceiling height genuinely allows them — a false beam in an eight-foot ceiling makes a small room smaller.

Where the casita goes on the lot

State law gives you a floor to work from: a city must allow a detached ADU of at least 800 sq ft with four-foot side and rear setbacks, and may not cap ADU size below 850 sq ft, or 1,000 sq ft with more than one bedroom. The commonly quoted 1,200 sq ft is the state default cap for a detached ADU (Gov. Code 66314(d)(5)), which a city may raise and which Los Angeles has adopted. Beyond the numbers, four things decide where the building actually lands:

• The sewer lateral and the water line. Where they run, and how deep, often matters more than where you would prefer the building to sit. A sewer camera at the feasibility stage is cheap and occasionally saves a redesign.
• Trees. Protected trees, and root zones generally, constrain foundations. Find out early whether anything on or near your lot is protected.
• Sun and sightlines. Windows that look straight into the main house’s bedrooms make both households uncomfortable. Rotating the plan a few degrees, or moving one window, usually fixes it at no cost.
• The driveway. No replacement parking is required when a garage is converted, but construction access, and later everyday parking, still have to work.

What a casita costs in Los Angeles

Style choices sit inside those ranges rather than on top of them, but they are not free. Clay tile costs more than composition and needs the framing to suit it; true divided-light wood windows cost several times what vinyl does; deep window reveals mean thicker wall assemblies or added trim. None of it is extravagant on its own, and together it is the difference between a casita and a shed with an arch. Decide which details you care about early, because they are cheapest to build in and most expensive to add.

Impact fees cannot be charged on a unit of 750 sq ft or less, so that threshold is worth knowing before the plan is drawn. Financing routes are covered on our ADU financing options page.

Permits, and what catches people out

• The kitchen decision is a permit decision. A wet bar with a hot plate and a full-size refrigerator can be read as cooking facilities. Decide what you are building and put it on the plans.
• Solar. A newly constructed detached unit is generally subject to the solar requirement for new residential construction; a conversion of an existing structure is not. That changes the roof design and the budget.
• Fire sprinklers are not required in the new unit if the existing house does not have them.
• Design review. In a historic preservation overlay zone or a homeowners association, the style of the casita is not only your choice. Find out before you fall in love with a drawing.
• Three units is the floor on a single-family lot in state law — a conversion ADU, a junior ADU and a new detached unit. A casita need not be your only addition.

Rules stacked on top of the state minimums vary by city. Our Los Angeles ADU rules by city page and ADU rules calculator are the quickest way to see what applies at a specific address, and the state’s ADU Handbook is the authoritative reference.

Casita FAQs

What is a casita?

A casita is a small separate living space on the same property as a main house. The word is Spanish for “little house.” In Southern California it normally describes a detached backyard unit styled to match a Spanish or Mediterranean home, and it is permitted as an accessory dwelling unit.

Is a casita the same as an ADU?

In practice, usually yes. “Casita” is a description of style and scale with no legal meaning in California; “ADU” is a category defined in state law. A casita with a kitchen is permitted as an ADU. A casita without one is an accessory structure and cannot be lived in as a separate home.

Does a casita need a kitchen?

Only if you want it to be an independent dwelling — and that is normally the point of building one. Cooking facilities are what turn a building into a dwelling unit under Government Code section 66313 and under the Los Angeles Municipal Code.

Can you rent out a casita in California?

Yes, if it is permitted as an ADU or junior ADU, on a lease longer than 30 days. Short-term rental is not permitted, and individual cities may be stricter. An ADU cannot be sold separately from the main house on a single-family lot. Our page on ADU rental income in Los Angeles puts current rent benchmarks against build cost.

How big can a casita be?

State law sets floors rather than a ceiling: a city may not cap an ADU below 850 sq ft, or below 1,000 sq ft with more than one bedroom, and must allow at least 800 sq ft with four-foot side and rear setbacks. The 1,200 sq ft figure quoted on most websites is the state’s default cap for a detached ADU (Gov. Code 66314(d)(5)), which the City of Los Angeles and many other cities have written into their ordinances; it is not a statewide maximum, and a city is free to allow more.

What is the difference between a casita and a pool house?

A pool house is an accessory structure for changing, storage and shade, often with a bathroom and no kitchen, and nobody may live in it as a separate residence. A casita built as an ADU has a kitchen, a bathroom and its own entrance, and is a legal home. The buildings can look identical from the outside; the permits are not the same.

Do I need a permit to build a casita?

Yes. New construction, conversions, plumbing, electrical and structural work all require permits, and an ADU is reviewed against both the state standards and your city’s ordinance. Unpermitted backyard units surface at resale, at refinance and at insurance claim time.

How much does a casita cost to build in Los Angeles?

Typical Los Angeles budgeting ranges are $100,000 to $200,000 for a garage converted into a casita and $180,000 to $450,000 and up for a new detached unit, depending on size. A junior ADU built inside the house runs $60,000 to $150,000. Style choices such as clay tile and wood windows sit inside those ranges but push toward the upper end.

Thinking about a casita?

The first question is never the tile. It is whether your lot, your setbacks, your utilities and your city’s ordinance support the building you have in mind, and what it will realistically cost. We will walk the property, tell you what is possible at your address, and put a written range against it. Site visits take about two hours; a written proposal follows within 48 hours.

A mother-in-law suite is a self-contained living space for a family member on the same property as the main house. In California it is not a legal category, so the building department will classify whatever you build as a junior ADU, an ADU, or simply a bedroom suite — and that classification, not the name you use for it, decides the permit path, the cost and whether the space could ever be rented. In Los Angeles County the typical budgeting ranges are $60,000 to $150,000 for a junior ADU built inside the house, $100,000 to $200,000 for a garage conversion, and $180,000 to $450,000 and up for a new detached unit.

Green Design and Build is a licensed general contractor (CSLB #1110975) based in Van Nuys. We design and build ADUs and junior ADUs, as well as room additions, across Los Angeles, Orange and Ventura counties and the western Inland Empire. The figures on this page are typical Los Angeles budgeting ranges, not a quote — every lot, every house and every family is different.

What counts as a mother-in-law suite in California?

Legally, nothing does. “Mother-in-law suite” and “in-law suite” are household terms. They appear in no California statute and in no Los Angeles zoning definition. What the plan checker looks at is much narrower: does the space have permanent provisions for cooking?

Under Government Code section 66313, a dwelling unit is an independent living facility with permanent provisions for living, sleeping, eating, cooking and sanitation. The Los Angeles Municipal Code says much the same thing: a dwelling unit is a group of rooms, one of which is a kitchen. Add a kitchen and you have created a second home on the lot, with everything that follows. Leave the kitchen out and you have built a very nice bedroom.

That single decision sorts every mother-in-law suite into one of three buckets.

Our guide to what an ADU is and what all the different names mean maps the rest of the vocabulary — granny flat, casita, backyard cottage, guest house — onto the same three categories.

The four ways to build one

Most families arrive with a picture in their head and no idea which of these it is. The differences matter more than the picture does.

If the parent moving in is still driving, still cooking and wants their own front door, an ADU is the honest answer. If they need someone within earshot at night, a junior ADU or an interior suite usually serves the family better — and costs a fraction as much. We walk through the trade-off in more depth in ADU vs. room addition and detached ADU vs. garage conversion.

Designing it for someone who plans to stay

This is the part most mother-in-law suite articles skip, and it is the part that decides whether the space still works in ten years. A single-family home in California is not required to meet accessibility standards. That is exactly why it is worth borrowing from them on purpose, while the walls are open and the changes are nearly free.

Get in without a step

One zero-step entry is worth more than every other accessibility feature combined. On a garage conversion it is usually straightforward, because the slab is already close to grade. On a new detached unit it means planning the pad height and the walkway slope at the site-plan stage, not discovering the problem after the foundation is poured. A gentle ramped walk reads as landscaping; a bolt-on ramp added later reads as a hospital.

Doorways, hallways and turning space

Accessible-design standards use 32 inches of clear opening as the target for a doorway, which in practice means specifying a 36-inch door — the leaf, hinges and stop eat the difference. Nothing obliges you to do this in a single-family home. It also costs almost nothing at framing and is expensive to retrofit. The same logic applies to a 5-foot clear circle in the bathroom and bedroom for a walker or wheelchair to turn, and to pocket or barn doors where a swinging door would block the path.

Put the money in the bathroom

Falls happen in bathrooms. Three decisions matter, and all three are cheapest now:

• A curbless shower rather than a tub or a threshold. Our walk-in shower guide covers how the slope, the drain and the waterproofing have to be planned together for a curbless floor to work.
• Blocking in the walls. Plywood or 2x lumber fastened between the studs before drywall, behind the shower walls and beside the toilet, so grab bars can later be screwed into solid wood instead of hollow drywall anchors. It adds a few hundred dollars during framing. Adding it afterwards means opening and re-tiling the wall.
• A comfort-height toilet and a hand-held shower on a slide bar. Both are ordinary fixtures at ordinary prices; you simply have to specify them.

Install the grab bars or not, as your family prefers. The point is to make installing them later a thirty-minute job.

The kitchen, whichever kind you are allowed

A junior ADU gets an efficiency kitchen: a cooking appliance, a food preparation counter, storage cabinets and a sink. The state housing department has been explicit that cities may not dictate the size of the counter or cabinets, the specific electrical or gas connections, or the type of appliance — so an induction cooktop and a compact oven on a 20-amp circuit can satisfy the requirement without running a gas line. That matters for cost and it matters for safety: an induction cooktop with automatic shut-off is a reasonable choice for someone who forgets a pan.

Beyond that, pull-out shelves instead of deep base cabinets, a shallow sink so the drain does not sit at knee height, lever handles rather than knobs, and drawers at waist height. None of this looks medical. All of it survives a change in circumstances.

Light, floors and sound

Older eyes need considerably more light than younger ones, and contrast matters as much as brightness: a light floor against a dark door frame is easier to read than a beautifully tonal scheme. Choose flooring with slip resistance rather than shine, avoid thick rugs and transition strips, and put a switched light on the path between bed and bathroom. Title 24 already pushes California new construction toward efficient lighting; plan the layout so it lands where it is useful.

Privacy is a layout problem, not a construction problem

Multigenerational households fail over small frictions, not big ones. The ones we hear about most:

• Sound through a shared wall. A junior ADU shares at least one wall with the house. Insulating that wall, using a solid-core door and offsetting the electrical boxes so they do not sit back to back in the same stud bay costs very little during framing and is the difference between two homes and one noisy one.
• Where the front door faces. A separate entrance is required for a junior ADU and standard for an ADU, but where it points is a choice. Facing it away from the main house’s living room gives both households the feeling of arriving somewhere of their own.
• Outdoor space. A small patio, a bench, somewhere to sit that is not the family’s backyard. Fencing is rarely the answer; planting usually is.
• Laundry. Decide early. A stacked washer-dryer inside the unit removes a daily negotiation; sharing the house’s laundry saves the plumbing and the square footage.
• Parking. State law does not require you to replace parking you lose in a garage conversion, but the car still has to go somewhere. Work out the driveway before, not after.

The rules that actually apply

If your mother-in-law suite is a junior ADU or an ADU, state law does a lot of the work for you. The provisions that surprise people most:

• Owner-occupancy for a junior ADU is now conditional. Current state law requires the owner to live in either the house or the junior ADU only where the junior ADU shares sanitation facilities with the house. Give it its own bathroom and the requirement falls away. Some city ordinances were written before this change and still show a blanket requirement — ask your building department which version they are applying to your permit.
• A deed restriction is recorded on a junior ADU. It runs with the land, prohibits selling the unit separately from the house, and records its size and attributes. It is routine, but your lender and your title company should see it early.
• Three units is the floor on a single-family lot. State law contemplates a conversion ADU, a junior ADU and a new detached ADU on the same single-family lot. So housing a parent now does not necessarily use up your options later.
• No impact fees at 750 sq ft or less, and proportionate fees above that.
• No replacement parking when a garage is converted, and no fire sprinklers in the new unit if the existing house does not have them.
• A lease longer than 30 days is the minimum in practice. State law lets a city require that an ADU or junior ADU be rented only for terms longer than 30 days, and the City of Los Angeles and every city on our ADU rules pages do, so short-term rental is out.
• Size is set locally. A city may not cap an ADU below 850 sq ft, or below 1,000 sq ft with more than one bedroom, and must allow at least 800 sq ft with four-foot side and rear setbacks. The 1,200 sq ft you see quoted is the state default cap for a detached ADU (Gov. Code 66314(d)(5)), which a city may raise; a city may also set a lower ceiling, but never one below the 850/1,000 floor.

The authoritative reference is the California Department of Housing and Community Development’s ADU Handbook; the size provisions above are in Government Code section 66321 and the junior ADU provisions in section 66333. Rules on top of the state floor vary by city, which is why we keep a page of Los Angeles ADU rules city by city and an ADU rules calculator for a specific address.

Can you rent it out later?

If it is an ADU or junior ADU, yes — on a lease longer than 30 days. If it has no kitchen, no: it is part of your house, and renting it as a separate dwelling is not legal.

This is worth thinking about before you design, because families change. A suite built with no kitchen is the cheapest thing to build and the hardest thing to repurpose — converting it to an ADU later means a second permit, a kitchen, and often a separate entrance and utility work you could have roughed in the first time. If there is any chance the space becomes a rental, running the plumbing and the electrical for a future kitchen while the walls are open is inexpensive insurance. Our page on ADU rental income in Los Angeles puts current rent benchmarks against build cost.

Neither an ADU nor a junior ADU can be sold separately from the main house on a single-family lot.

How long it takes

From the first conversation to a parent moving in, plan on six months to a year for an ADU. A junior ADU inside existing space is usually the fastest; a new detached unit the slowest.

Families often come to us with a deadline attached — a lease ending, a hospital discharge, a house being sold in another state. Say so at the first meeting. It changes which of the four options we recommend, and it is the single most useful piece of information you can give a contractor.

A real example: a garage by the pool

One of our Los Angeles projects converted a detached garage beside a pool into a complete one-bedroom unit: the roof structure was rebuilt, new windows were cut in, the shell was sheathed, waterproofed and stuccoed, and the interior finished with a full kitchen, a tiled bathroom and French doors onto the yard. It is the shape most families picture when they say “mother-in-law suite” — separate, private, and close enough to walk over for dinner.

More photographs from the build are on the garage-to-ADU conversion project page, and costs are broken down on our garage conversion cost page.

Mistakes we see

• Building the kitchen by accident. A wet bar with a sink, a hot plate and a full-size refrigerator can read to a plan checker as cooking facilities. If your intention is a bedroom suite, design it as one deliberately and say so on the plans.
• Designing for today’s health, not next decade’s. A step down into a sunken living area, a tub-shower, a 30-inch door. Every one of them is cheap now and costly later.
• Forgetting the electrical panel. Many San Fernando Valley houses from the 1950s to 1970s need a service upgrade before a second unit can be added. It is a real line item, not a surprise your contractor should spring on you mid-project.
• Legalizing an existing conversion the wrong way. A garage someone converted years ago without permits follows a different path from a permitted structure being converted today. Get that classified correctly before you spend money on drawings.
• Skipping the deed restriction conversation with the lender. Junior ADU deed restrictions are routine, but they should not be the first your lender hears of it.
• Assuming a suite for a parent cannot also be an investment. Built as an ADU, it houses your family now and is a legal rental later. Built as a bedroom, it is neither.

What to ask before you sign

1. Which of the four categories are you proposing to permit this as, and why that one?
2. Does my lot and my city’s ordinance allow it, and what is the size ceiling at my address?
3. Does my electrical service need upgrading, and is that in the price?
4. What is the allowance for blocking, wider doors and a curbless shower, and what would it cost to add them now?
5. Who pulls the permit, and what happens to the schedule if plan check comes back with corrections?
6. What is not included in this number?

Quotes for the same project routinely differ by six figures, almost always because they cover different scopes. We explain what drives that in why ADU quotes vary so much between contractors. Whoever you hire, verify the CSLB license first.

Where we build mother-in-law suites

We work throughout Los Angeles County and the San Fernando Valley, across Orange County, in Ventura County, and in the western Inland Empire including Ontario and Rancho Cucamonga. Our office is in Van Nuys. Every city sets its own layer of rules on top of the state minimums, so the first step is always the same: check the ordinance for your address before anyone draws anything.

Mother-in-law suite FAQs

What is a mother-in-law suite?

A mother-in-law suite is a private living space for a relative on the same property as the main house. It is an everyday term rather than a legal one. In California the same space is permitted as a junior ADU, an ADU or an ordinary bedroom suite depending on whether it has cooking facilities and where it sits on the lot.

Is a mother-in-law suite the same as an in-law suite?

Yes. “In-law suite”, “mother-in-law suite”, “granny flat” and “casita” all describe the same idea in ordinary speech. None of them is defined in California law, so a building department will not use any of them on your permit.

Does a mother-in-law suite need its own kitchen?

Only if you want it treated as an independent home. Cooking facilities are what turn a suite into a dwelling unit under Government Code section 66313 and under the Los Angeles Municipal Code. Without a kitchen it stays part of your house: simpler to permit, but it cannot be rented separately.

Do I need a permit to build a mother-in-law suite in California?

Yes. Adding or converting living space, adding a bathroom, or altering plumbing, electrical or structure all require permits, whichever category the space falls into. Unpermitted work surfaces at resale, at refinance and at insurance claim time.

Can I rent out a mother-in-law suite?

If it is permitted as an ADU or junior ADU, yes, on a lease longer than 30 days; short-term rental is not allowed. If it has no kitchen it is part of your house and cannot be rented as a separate dwelling. Neither an ADU nor a junior ADU can be sold separately from the main house.

Do I have to live on the property?

For an ADU, no. For a junior ADU, only if it shares sanitation facilities with the main house — give it its own bathroom and the requirement does not apply. Ordinances written before this change may still show a blanket requirement, so confirm with your building department.

Will a mother-in-law suite raise my property taxes?

Building new living space is new construction, so the county assessor adds the assessed value of what you built to your existing assessment. Your original home is not reassessed. California also has a separate exclusion from reassessment for construction that makes a home accessible for a severely and permanently disabled resident — whether it applies to your project is a question for your county assessor, and worth asking before you build.

How much does a mother-in-law suite cost in Los Angeles?

Typical Los Angeles budgeting ranges are $60,000 to $150,000 for a junior ADU inside the house, $100,000 to $200,000 for a garage conversion, $180,000 to $450,000 and up for a new detached unit, and $130,000 to $250,000 for a 350 to 500 sq ft attached bedroom-and-bathroom addition with no kitchen. Converting space you already have costs considerably less than adding square footage. Financing options are covered on our ADU financing page.

Talk to us about your parents’ suite

The useful first conversation is not about finishes. It is about who is moving in, what they can manage today, what they may need in five years, and what your lot and your city actually allow. We will walk the property, tell you which of the four options fits, and put a written range against it. Site visits take about two hours and a written proposal follows within 48 hours.

Homeowners ask us the same question in almost every ADU consultation: will the rent cover what the unit costs to build? This page puts two public numbers side by side so you can answer it for your own lot: what an ADU typically costs to build in Southern California, using the same budgeting ranges we publish across this site, and what a unit of that size rents for, using the U.S. Department of Housing and Urban Development’s Fair Market Rents for fiscal year 2026. Everything here is an estimate, not a quote and not financial advice; the point is to show the order of magnitude before you spend money on drawings.

What an ADU rents for: HUD Fair Market Rents, FY 2026

HUD publishes a Fair Market Rent for every metro area each fiscal year. It is the 40th-percentile gross rent (rent plus utilities) for a modest, recently rented unit, so roughly 40 percent of comparable rentals lease for less and 60 percent for more. It is the figure the Section 8 program pays against, and it is a conservative benchmark for a new, well-finished ADU. The FY 2026 figures took effect on 1 October 2025. HUD later revised the Fair Market Rents for seven areas, Los Angeles-Long Beach-Glendale among them, effective 21 May 2026. The Los Angeles County row below uses those revised figures; the Orange, Ventura and Riverside-San Bernardino areas were not revised.

Build cost against rent: simple payback by ADU type

The table divides our published Southern California budgeting range for each ADU type by twelve months of the Los Angeles County Fair Market Rent for a unit of that size. “Simple payback” means years of gross rent needed to equal the build cost, before vacancy, taxes, insurance, maintenance, management or loan interest. It is a screening number, not a return on investment.

Two things stand out. A garage conversion is the fastest to pay back because the slab, walls and roof already exist, which is why so many San Fernando Valley ADUs start as garage conversions. And the jump from a 500 sq ft one-bedroom to an 800 sq ft two-bedroom adds roughly $575 a month of rent at the Los Angeles benchmark but $45,000 to $90,000 of cost, so the larger unit pays back over a similar or slightly longer period; it makes more sense when a two-bedroom suits the household or the lot than as a pure income play.

The same math in Orange, Ventura, Riverside and San Bernardino counties

What the simple payback leaves out

• Vacancy and turnover. Budget for at least a few weeks empty between tenants and for repainting and repairs at turnover.
• Property tax. In California the new construction is assessed and added to your tax bill; the existing house is not reassessed. Ask the county assessor how they value ADUs before you build.
• Insurance, utilities and maintenance. A rented ADU usually means a landlord policy and, if the unit is not separately metered, utilities you pay and recover through rent.
• Financing. Interest changes the picture more than any other line. Our ADU financing options guide compares HELOCs, cash-out refinances, renovation loans and construction loans, and explains how some lenders count expected ADU rent toward qualifying.
• Rent rules. State law requires ADU leases of longer than 30 days, so short-term rental income is not part of this math. Local rent regulations may apply to the unit; check with the city before setting expectations.
• Resale value. The unit adds value at sale as well as rent, but appraisers value ADUs inconsistently. Treat resale as upside, not as part of the payback.

What changes the answer on your lot

The cost side moves more than the rent side. A garage with a sound slab and a 200-amp panel nearby sits at the bottom of the range; a detached unit on a hillside lot, in a fire zone, or with a long sewer run to the street sits at the top. What your city lets you build sets the size, and size sets the rent: use the city-by-city ADU rules table or the California ADU rules calculator to see whether a 500 sq ft one-bedroom or an 800 sq ft two-bedroom is realistic on your lot, then read how long an ADU takes, because months of design and permitting are months without rent.

ADU rental income FAQs

How much rent can an ADU earn in Los Angeles?

HUD’s FY 2026 Fair Market Rent for Los Angeles County, as revised effective 21 May 2026, is $2,079 for a studio, $2,328 for a one-bedroom and $2,903 for a two-bedroom, including utilities. A new ADU in a strong neighborhood often rents above those figures; the FMR is a conservative benchmark, not a ceiling.

Which ADU pays for itself fastest?

A garage conversion, because the structure already exists: at $100,000 to $200,000 against a one-bedroom benchmark rent of $2,328 a month in Los Angeles County, the simple payback is roughly three and a half to seven years of gross rent, before expenses.

Can I rent my ADU on Airbnb?

Not under state ADU law, which requires rentals of longer than 30 days. Cities enforce this through the ADU permit conditions.

Will building an ADU raise my property taxes?

The new construction is assessed and added to your bill; the existing home keeps its current assessment. The county assessor can tell you how they value ADUs, and a tax professional can tell you how the rent and the new assessment interact for you.

Get real numbers for your lot

A two-hour site visit tells us which unit your lot can take, where the sewer and panel are, and what the realistic budget is; a written proposal follows within 48 hours. Request a free estimate or read more about how we design and build ADUs across Southern California.

Planning an ADU for rental income?

We will walk the site, confirm what your city requires, and send an itemized written proposal with every allowance named. The site visit and the estimate are free.

An accessory dwelling unit is a second, complete home on a lot that already has a house on it. California law defines it as a unit with permanent provisions for living, sleeping, eating, cooking and sanitation — and that word “cooking” is the whole test. A structure with a bedroom and a bathroom but no kitchen is not an ADU. Add a kitchen and it is. Everything else people argue about, including whether to call it a granny flat, a casita or a mother-in-law suite, is vocabulary rather than law. Green Design and Build is a licensed general contractor (CSLB #1110975) based in Van Nuys that designs, permits and builds ADUs across Los Angeles County, Orange County, Ventura County, western Riverside County and western San Bernardino County.

We are led by Dekel Sofer, who has more than 16 years of hands-on construction experience; the company has completed hundreds of projects and holds a 4.7-star rating across 146 reviews on Yelp. The state rules below apply everywhere in California. The Los Angeles specifics are called out separately, because the local half of this varies by city.

The legal definition, and the one word that decides it

Under Government Code section 66313, an accessory dwelling unit is an attached or detached residential dwelling unit that provides complete independent living facilities for one or more people, on a lot with an existing or proposed primary residence. It must include permanent provisions for five things: living, sleeping, eating, cooking and sanitation. An efficiency unit and a manufactured home both count.

Four of those five are easy. The fifth is the line everything turns on. The City of Los Angeles makes it even blunter in its own zoning code, which defines a dwelling unit as a group of two or more rooms, one of which is a kitchen, designed for occupancy by one family. No kitchen, no dwelling unit. That single distinction decides whether your project is an ADU with state protection behind it, or an accessory building with none.

Every other name for an ADU

Most people searching for this do not use the letters A-D-U. They use a word they grew up with. None of the terms below is defined anywhere in California statute or in the Los Angeles Municipal Code; the state’s own housing department acknowledges as much, noting that ADUs “have been known by many names: granny flats, in-law units, backyard cottages, secondary units and more.”

The practical consequence is simple: if you ask a building department for a granny flat, nobody will know what standard to apply to you. Ask for an accessory dwelling unit and a specific, generous body of state law attaches to your application.

The four kinds of ADU

Our guides compare a detached ADU against a garage conversion and weigh an ADU against a room addition if you are deciding between them.

What a junior ADU actually is

A JADU is no more than 500 square feet of interior livable space, contained entirely within the walls of a single-family residence. It is the cheapest way into an ADU because you are not building a structure, and it is the most misunderstood. The rules:

• One JADU per residential lot.
• It needs its own exterior entrance, separate from the main entrance to the house.
• It needs an efficiency kitchen: a cooking facility with appliances, plus a food preparation counter and storage cabinets sized reasonably for the unit. Notably, the state housing department has said cities may not dictate counter or cabinet sizes, specific electrical or gas connections, or appliance types.
• Sanitation can be shared with the house or separate.
• A deed restriction is recorded, prohibiting sale of the JADU separately from the house.
• Rentals must be longer than 30 days, so no short-term letting.
• Owner-occupancy changed on 1 January 2026. Under AB 1154, it is now required only where the JADU shares sanitation facilities with the house. Give the JADU its own bathroom and the owner-occupancy requirement falls away. Local ordinances written before 2026 may still show the old blanket rule; state law governs.

Our junior ADU cost guide covers what one costs to build.

How small can an ADU be?

Smaller than most people expect. California’s Health and Safety Code allows an efficiency unit with a minimum floor area of 150 square feet for occupancy by up to two people, and state ADU law separately forbids a city from setting a minimum ADU size that would prohibit an efficiency unit. So a 150-square-foot ADU is legal in principle anywhere in California.

You may also see 190 square feet quoted as the minimum. That number is real, but it is not an ADU minimum: it is the living-room size for an “efficiency dwelling unit” in California Building Code section 1208.4, which was 220 square feet until the 2022 code reduced it to 190. State ADU law points instead to the Health and Safety Code efficiency unit of 150 square feet and bars a city from setting an ADU minimum that would prohibit one. Ask your building department which figure it applies.

Separately, the Residential Code sets habitability floors that apply to any room: habitable rooms other than kitchens must be at least 70 square feet and at least 7 feet in any horizontal direction, with ceilings at least 7 feet high, or 6 feet 8 inches in a bathroom or laundry.

How big can an ADU be?

There is no statewide maximum. State ADU law sets floors that every city ordinance has to clear and then leaves the ceiling to the city. Under Government Code section 66321, a local agency may set minimum and maximum ADU sizes, but it may not adopt:

• a maximum below 850 square feet of interior livable space;
• a maximum below 1,000 square feet for an ADU with more than one bedroom; or
• any lot coverage, floor area ratio, open space, front setback or minimum lot size rule that stops you building an ADU of at least 800 square feet with four-foot side and rear setbacks.

The 1,200 square feet quoted on most ADU websites comes from the state’s standard for a detached ADU (Gov. Code 66314(d)(5)), which each city then writes into its own ordinance. The City of Los Angeles allows a detached ADU up to 1,200 square feet where the lot’s own standards allow it, and many Southern California cities settled on the same number — but a city may adopt a more permissive ordinance and allow a larger unit. The only way to know your ceiling is to read the ordinance for your address; our Los Angeles ADU rules by city page is the starting point.

Bigger is not automatically better. Impact fees cannot be charged on an ADU of 750 square feet or less, and above that they have to be proportionate to the primary dwelling, so crossing 750 square feet changes the fee picture as well as the build cost. Our ADU cost guide covers where the money actually goes.

How many can you have on one lot?

On a single-family lot, three, as a floor rather than a ceiling. State law requires cities to ministerially approve a combination of: one ADU created within existing space, one junior ADU, and one newly constructed detached ADU. That is three additional units alongside the primary residence, and the state housing department’s own handbook states it in those terms. A city may allow more under its own ordinance; it may not allow fewer.

ADUs also do not count against your lot’s allowable density. Government Code section 66319 says an ADU is an accessory use that “shall not be considered to exceed the allowable density for the lot.” Do not over-read that, though: ADUs are still counted as housing units in the state’s regional housing reporting. It means your zoning does not block them, not that they are invisible.

A guest house is not an ADU, and in Los Angeles it has its own rules

This is where most published advice goes wrong, and it matters, because “can I just build a guest house instead” is one of the most common questions we get.

First, the Los Angeles Municipal Code does define “Guest House” — but not the way you think. In the LAMC a Guest House is a dwelling containing not more than five guest rooms or suites of rooms with no kitchen facilities. That is a lodging definition. The backyard building homeowners mean is a different defined term: Accessory Living Quarters, which the code describes as an accessory building used solely as the temporary dwelling of guests of the occupants, having no kitchen facilities and not rented or otherwise used as a separate dwelling unit.

You can still build one in Los Angeles. The catch is in the zoning: in the R1 zone, accessory living quarters may not be located on a lot having an area of less than 10,000 square feet (other residential zones set their own thresholds). Most Valley and South Bay lots are well under that. And unlike an ADU, an accessory living quarters gets no state protection at all — no guaranteed four-foot setbacks, no ministerial approval, no minimum size the city must allow. You are entirely in the hands of local zoning.

What counts as a “kitchen” for this purpose is more expansive than a stove. The City’s zoning interpretation manual has historically treated a natural gas outlet, a 220-volt outlet, a double sink, a bar sink over one square foot, a hot water line to a bar sink, a refrigerator over 10 cubic feet, a garbage disposal, a dishwasher or the space for one, any device designed for cooking or heating food, and more than 10 square feet of counter as kitchen facilities. That is interpretive guidance rather than code text, and it dates from an older edition of the manual, so confirm the current position with the department — but it tells you how carefully this line is policed.

And if you build a kitchen-less guest room and quietly add a kitchen later? It stops meeting the accessory living quarters definition and becomes an unpermitted dwelling unit. That is a code enforcement problem, not an upgrade. The lawful route is to permit it as an ADU from the start — which, given the state protections an ADU carries and the 10,000-square-foot lot rule a guest house does not escape, is usually the easier path anyway.

Movable tiny houses

The City of Los Angeles recognizes a category most cities do not. A Movable Tiny House is registered with the DMV, meets ANSI 119.5 or NFPA 1192 standards, cannot move under its own power, and measures between 150 and 430 square feet. In Los Angeles it can serve as an ADU. Treat this as a City of Los Angeles answer only: other jurisdictions handle tiny houses on wheels very differently and many do not accept them as ADUs at all.

What if there is already a unit back there?

Two different pathways, and they get blurred constantly.

A lawfully permitted structure with no kitchen — a guest room, a rec room, a garage — converts under the state’s conversion provision. The city must approve it ministerially, and you are allowed up to 150 square feet of expansion beyond the existing footprint purely to create entry and exit. The work is adding a compliant kitchen and bringing the building up to habitability standards.

An unpermitted unit someone has been living in is a different statute. Government Code section 66311.7 (which you may see cited by its old number, 66332) lets you legalize a unit built before 1 January 2020. The city cannot deny the permit for building-standard violations or for failing to meet the local ADU ordinance, and cannot charge impact fees. Los Angeles implements it through a documented process with a health-and-safety checklist, and the unit may comply either with current codes or with the codes in effect when it was built. You will need to evidence the construction date — utility bills, leases, contractor receipts.

This Los Angeles project is a garage conversion: the same footprint, a new kitchen with full appliances, a bathroom, and French doors where the garage door used to be. Once that kitchen went in, the building stopped being a garage and became a dwelling unit, with everything that follows from it. The full sequence is on the garage-to-ADU conversion project page.

How common are ADUs now?

Common enough to have changed what California builds. According to the state housing department’s March 2026 ADU handbook, ADUs permitted annually across California grew from 1,336 in 2016 to 30,354 in 2024, and in 2024 they made up more than 26.6 percent of all homes permitted statewide. Those are permits rather than finished buildings, so treat them as a measure of intent as much as output — but better than one in four homes permitted in California being an ADU is a genuine shift, and it is why the law keeps moving in their favor.

What it costs and how long it takes

Covered properly in their own guides rather than summarized badly here: what an ADU costs to build, what a garage conversion costs, how long an ADU takes, and how homeowners pay for them. If quotes you have received vary wildly, there are specific reasons for that.

For what your particular lot allows, we publish ADU rules by city across Southern California, an ADU rules calculator, and a guide to the LADBS standard plan program, which is the shortcut most homeowners miss.

Where we build ADUs

We build ADUs from our Van Nuys office across the San Fernando Valley, the rest of Los Angeles County, Orange County, Ventura County, western Riverside County and western San Bernardino County. The mix changes by area: garage conversions dominate in the older Valley neighborhoods where detached garages sit at the back of the lot, detached new construction is more common on the wider lots of the Inland Empire and outer Orange County, and junior ADUs make the most sense in larger houses where a wing can be separated off. See our ADU construction service and all of our service areas.

ADU FAQs

What is an ADU?

An accessory dwelling unit is a second, self-contained home on a lot with an existing or proposed primary residence. California law requires it to have permanent provisions for living, sleeping, eating, cooking and sanitation. In practice the kitchen is the defining feature: a structure with a bedroom and bathroom but no kitchen is not an ADU. It can be detached, attached to the house, or created inside existing space such as a garage.

Is a granny flat the same as an ADU?

Yes. “Granny flat” is a colloquial term with no definition in California statute or in the Los Angeles Municipal Code. So are mother-in-law suite, in-law suite, casita, backyard cottage, secondary suite and carriage house. The state housing department itself notes ADUs have been known by many names. Use “accessory dwelling unit” when you apply for a permit, because that is the term the law attaches to.

What is the difference between an ADU and a guest house?

A kitchen. An ADU has one; a guest house does not, and without one it is not a dwelling unit. In Los Angeles the backyard version is formally called accessory living quarters, and it may not be built on a lot smaller than 10,000 square feet in the R1 zone. A guest house also gets none of the state protections an ADU receives, such as guaranteed four-foot setbacks and ministerial approval, so on most lots the ADU route is both easier and more useful.

What is a junior ADU?

A JADU is up to 500 square feet of interior livable space created entirely within the walls of a single-family house, including an attached garage. It needs its own exterior entrance and an efficiency kitchen with a cooking facility, appliances, a food preparation counter and storage. Sanitation may be shared or separate, and a deed restriction is recorded against the property. Since 1 January 2026, owner-occupancy is required only where the JADU shares a bathroom with the house.

How many ADUs can I build on my property?

On a single-family lot, state law requires cities to allow a combination of one ADU created within existing space, one junior ADU, and one newly built detached ADU — three additional units alongside the house. That is a minimum, not a maximum; a city may permit more. ADUs also do not count toward your lot’s allowable density.

How small can an ADU be?

California allows an efficiency unit with a minimum floor area of 150 square feet for up to two occupants, and a city may not set an ADU minimum size that would prohibit one. Habitability rules still apply: habitable rooms other than kitchens must be at least 70 square feet and 7 feet in any horizontal direction, with 7-foot ceilings. The 190 square feet often quoted online comes from the Building Code’s efficiency dwelling unit section (CBC 1208.4), not from ADU law.

Can I rent out an ADU?

Yes, for terms longer than 30 days. Cities may require, and in practice nearly always do require, a minimum 30-day rental term, which rules out short-term letting. A JADU carries the same 30-day floor. An ADU generally cannot be sold separately from the main house, though a small number of California cities have opted into a condominium pathway that allows it.

Can I legalize an unpermitted unit in my backyard?

Often, yes, if it was built before 1 January 2020. Government Code section 66311.7 requires cities to permit qualifying unpermitted ADUs and junior ADUs without denying them for building-standard violations or for failing the local ADU ordinance, and without charging impact fees. The unit may comply with either current codes or the codes in effect when it was built, and a health-and-safety review applies. You will need documentation of the construction date.

Find out what your lot actually allows

We will look at the lot, the setbacks, the existing structures and your city’s current ordinance, and tell you which of the three routes — conversion, junior ADU or new detached unit — makes sense on your property before anyone draws anything. The site visit takes about two hours, the written proposal follows within 48 hours, and both are free. We reply within one business day.

A junior accessory dwelling unit (JADU) is a unit of no more than 500 square feet of interior livable space created entirely inside an existing or proposed single-family house, including an attached garage, with its own entrance and an efficiency kitchen; it may share a bathroom with the main house. Because a JADU reuses the roof, walls and floor you already have, it is usually the least expensive legal way to add a second unit, and it pays no development impact fees. Green Design and Build is a licensed, bonded and insured general contractor (CSLB #1110975) based in Van Nuys, building ADUs, JADUs and garage conversions for homeowners across Los Angeles County, Orange County, Ventura County, western Riverside County and western San Bernardino County (Ontario, Rancho Cucamonga and neighboring cities).

We are led by Dekel Sofer; the company has completed hundreds of projects and holds a 4.7-star rating across 146 reviews on Yelp.

What a JADU is, in the words of the law

The rules for junior ADUs sit in California Government Code section 66333, and every city in our service area, including the City of Los Angeles, has to allow them. Verified against the Department of Housing and Community Development’s ADU Handbook (March 2026 edition), the definition has six parts:

1. Size. No more than 500 square feet. Since 1 January 2026 the statute measures “interior livable space,” so wall thickness does not count against you.
2. Location. Contained entirely within the single-family residence. An attached garage counts as part of the house, so converting an attached two-car garage into a JADU is the most common version we build. A detached garage cannot be a JADU; it becomes a garage conversion ADU instead.
3. Kitchen. An efficiency kitchen, which the statute defines as “a cooking facility with appliances, a food preparation counter, and storage cabinets that are of reasonable size in relation to the size of the JADU.” A city cannot demand a specific counter length, a 240-volt range circuit or a full-size stove.
4. Bathroom. A JADU “may include separate sanitation facilities or may share sanitation facilities with the existing structure.” If it shares, it must have its own exterior entrance and an interior door into the main living area.
5. Owner occupancy. Since 1 January 2026 (AB 1154), the owner must live in either the house or the JADU only when the JADU shares a bathroom with the house. Give the JADU its own bathroom and no owner-occupancy requirement applies. The requirement never applies when the owner is a government agency, land trust or housing organization.
6. Deed restriction. The city may require a recorded deed restriction that does two things and only two: prohibits selling the JADU separately from the house, and holds the unit to the size and attributes state law allows. The City of Los Angeles records it before the permit issues.

Two more rules matter. Only one JADU is allowed per lot. And no city may require parking for a JADU, even when it replaces an attached garage.

JADU plus ADU: the two-unit lot

The reason JADUs are worth knowing about is Government Code section 66323. On a single-family lot, a city must ministerially approve one ADU converted from existing space, one JADU, and one new detached ADU of up to 800 square feet with four-foot side and rear setbacks. That is how a standard 1950s Valley ranch house on a 6,000-square-foot lot ends up with three legal units: the house, a JADU in the attached garage, and a detached unit in the back yard. The detached unit is where most of the money and the rental value sit; the JADU is the inexpensive second one. Our ADU rules hub and the ADU rules calculator show the minimums your city has to allow for both.

How much does a JADU cost in Los Angeles?

A JADU in Los Angeles typically costs $60,000 to $150,000. That figure and every other on this page are typical Los Angeles budgeting estimates, not a price list or a quote. Your project can come in lower or higher depending on the house, the scope and the finishes; the only real number is a written proposal after a site visit.

The ceiling to compare against is the published range for a garage conversion ADU, $100,000 to $200,000, because a JADU built in an attached garage is the same shell with less plumbing: it can share the bathroom, and its kitchen is a cooking counter rather than a full kitchen with a range hood ducted through the roof. A JADU carved out of a bedroom wing with a new exterior door and no bathroom of its own sits at the low end; a garage JADU with its own bathroom, a new slab section for the drain, and a panel upgrade sits at the high end and overlaps the garage-conversion range.

The published ranges for other ADU types are in our guide to how much it costs to build an ADU on your property, and the garage figures are broken down in our garage conversion cost guide.

JADU vs ADU vs garage conversion

When a JADU beats a full ADU

A JADU is the right unit when the budget is the constraint, when the yard is not there, or when the second unit is for family rather than rent. It makes sense for a parent or an adult child who will share the house’s bathroom without friction, for a lot where a detached unit would eat the only outdoor space, and for a homeowner who wants a second permitted unit in months rather than a year. It is also the right first step on a lot that will eventually get a detached ADU too, because the JADU approval does not use up the detached-unit entitlement.

A full ADU is the better answer when rental income is the goal, because a 500-square-foot unit that shares a bathroom and has a hot plate rents for far less than a self-contained unit with its own kitchen and bath; when the only convertible space is a detached garage, which can never be a JADU; and when you do not want a deed restriction or an owner-occupancy condition on title. Our guides to detached ADU vs garage conversion and ADU vs room addition cover the other two decisions on the same lot.

Permits and the 60-day clock

A JADU is a ministerial permit, the same as an ADU. In the City of Los Angeles, including Van Nuys, Sherman Oaks, Encino, Studio City, Woodland Hills, Northridge and North Hollywood, the plans go to LADBS; Burbank, Glendale, Pasadena, Santa Clarita, every Orange County city and the western Riverside and San Bernardino County cities each run their own building divisions under the same state law. In Santa Clarita, where few houses have a detached garage to convert, a JADU is one of the usual routes; see our Santa Clarita ADU page. The agency has 15 business days to tell you whether the application is complete and then 60 days to approve or deny it. The deed restriction is recorded with the county before the permit issues, and the inspections are the ordinary building, electrical, plumbing and mechanical inspections plus the final.

Inside the house the code issues are practical rather than legal: a bedroom used as a JADU still needs an egress window, the wall and ceiling between an attached garage JADU and the house need the rated drywall and the self-closing door the residential code requires for a garage, and every sleeping room gets interconnected smoke alarms. None of it is hard; all of it should be on the drawings before plan check rather than discovered by the inspector.

How long does a JADU take?

A JADU is the fastest legal second unit because there is no foundation, no roof and usually no utility trenching. Design and drawings take a few weeks, plan check runs inside the statutory 60 days when the submittal is complete, and construction on an attached-garage JADU is measured in weeks rather than months: framing the door opening, rough electrical and any plumbing, insulation, drywall, the kitchen counter, flooring and finish. Six months to a year is the published range for an ADU project overall; a JADU sits at the short end of it, and our how long does an ADU take guide breaks the phases down.

A real garage that became a unit

Our garage-to-ADU conversion in Los Angeles, finished in 2025, shows what the fuller version of this work looks like: a detached two-car garage of about 500 square feet by the pool, with the roof structure rebuilt, new framing and sheathing, new windows and French doors where the garage door had been, stucco to match the tile roof, a full kitchen with an island, a tiled bathroom with a glass shower and wood-look flooring throughout, now a long-term rental. Because the garage was detached it had to be a full ADU rather than a JADU, with its own bathroom and a complete kitchen. A JADU in an attached garage keeps most of that scope and drops the parts that cost the most: the second bathroom’s plumbing and the full kitchen.

The other lesson comes from why ADU quotes vary so much between contractors: a garage conversion estimated at $85,000 to $95,000 that finished near $130,000 after the slab turned out to have no moisture barrier, the 100-amp panel had to become 200 amps, and a camera found root damage in the sewer line. Every one of those applies to an attached-garage JADU too, which is why our site walk starts with the slab, the panel and the sewer.

Where we build JADUs

We build JADUs and ADUs from our Van Nuys office across the San Fernando Valley and the rest of Los Angeles County, where the attached-garage ranch house is the natural JADU candidate; in Orange County, where master-planned communities add HOA review that state law limits but does not remove; in Ventura County; and in western Riverside County and western San Bernardino County, where newer slab-on-grade houses with three-car garages leave room for both a JADU and parking. See every city we serve on our service areas page, and the full picture of what we build on our ADU page and garage conversion page.

If you plan to finance the work, our financing page explains the programs we offer and how progress payments work under California law, and our ADU financing guide compares the loans homeowners use to fund a unit.

Junior ADU FAQs

How much does a junior ADU cost in Los Angeles?

A junior ADU in Los Angeles typically costs $60,000 to $150,000, a typical Los Angeles budgeting range and not a quote; a garage conversion ADU, the closest comparison, runs $100,000 to $200,000 in our published ranges. A JADU that shares the house bathroom and uses a plug-in efficiency kitchen sits at the low end; one with its own bathroom, a slab cut for a new drain and a panel upgrade sits at the high end. These are estimates, not a price list, and the only real number is a written proposal after a site visit.

What is the difference between a JADU and an ADU?

A JADU is limited to 500 square feet of interior livable space, must be inside the existing house or attached garage, needs only an efficiency kitchen, may share a bathroom with the house, and carries a deed restriction and, if the bathroom is shared, an owner-occupancy requirement. An ADU is a fully independent unit with its own kitchen and bathroom, can be detached or converted from a detached garage, can be larger, and has no owner-occupancy condition.

Do I have to live on the property if I build a JADU?

Only if the JADU shares a bathroom with the main house. Since 1 January 2026, California Government Code section 66333 lets a city require owner occupancy of a junior ADU only when the unit shares sanitation facilities with the house; a JADU with its own bathroom carries no owner-occupancy requirement. Some cities still record a covenant on every JADU, so ask before you file.

Can I have a JADU and a detached ADU on the same lot?

Yes. Government Code section 66323 requires cities to approve, on a single-family lot, one junior ADU and one ADU converted from existing space together with one new detached ADU of up to 800 square feet with four-foot side and rear setbacks. A JADU in the attached garage and a detached unit in the back yard is the most common two-unit layout we build in the San Fernando Valley.

Does a JADU need its own kitchen and bathroom?

A JADU needs an efficiency kitchen, which state law defines as a cooking facility with appliances, a food preparation counter and storage cabinets of a reasonable size for the unit; it does not need a full range or hood. It does not need its own bathroom and may share the house’s, in which case it must have a separate exterior entrance and an interior door to the main living area.

Can I convert my detached garage into a JADU?

No. A junior ADU must be contained entirely within the single-family residence, and an attached garage counts as part of the house but a detached garage does not. A detached garage becomes a garage conversion ADU instead, with a full kitchen and its own bathroom, which is a larger scope with a published Los Angeles range of $100,000 to $200,000.

Sources

The JADU rules on this page are California statute, which the Legislature amends most years; local ordinances are updated separately. The cost figures are our own, from conversions we have built. Confirm the current rules with your city before you commit.

• California HCD, Accessory Dwelling Unit fact sheet (April 2026) — the JADU rules, including that a JADU may share a bathroom with the single-family residence, and that impact fees may not be imposed on a JADU.
• California HCD, Accessory Dwelling Unit Handbook (March 2026) — Government Code section 66321(b)(3), the rule that local standards may not prevent at least an 800 sq ft ADU with four-foot setbacks at up to 16 feet.
• LADBS, Building Permits — the work that requires a permit in the City of Los Angeles, and the rule that building plans must be approved as a Building Plan Check before a permit is issued.

Last reviewed 17 September 2026.

Find out whether your garage should be a JADU or an ADU

Send us your address and a photo of the garage or the room you have in mind. We will walk the lot, check the slab, the panel and the sewer, tell you which unit the law and the house allow, and give you a written, itemized estimate. The site visit and the estimate are free.

A garage conversion ADU turns the slab, walls and roof you already have into a legal dwelling and typically costs $100,000 to $200,000 in Los Angeles; a detached ADU is a new building in the yard, costs $180,000 to $260,000 for about 500 square feet and $300,000 to $450,000 or more for about 1,000 square feet, and gives you a unit whose size, ceiling height, layout and position you choose. Green Design and Build is a licensed general contractor (CSLB #1110975) based in Van Nuys that builds both for homeowners across Los Angeles County, Orange County, Ventura County, western Riverside County and western San Bernardino County (Ontario, Rancho Cucamonga and neighboring cities). The conversion wins on cost and speed when the garage is sound and where you want the unit; the detached ADU wins when the garage is the wrong size, height or place, or when you want to keep the parking. These are typical Los Angeles budgeting estimates, not a price list or a quote, and your project can come in lower or higher.

We are led by Dekel Sofer. We hold a 4.7-star rating across 146 Yelp reviews and have completed hundreds of projects across all five counties. Our garage conversion and ADU pages describe each service; this guide is the comparison.

Garage conversion vs. detached ADU at a glance

These are typical Los Angeles budgeting estimates, not a price list or a quote. Your project can come in lower or higher depending on the house, the scope and the finishes; the only real number is a written proposal after a site visit. The figures are the ones on our pricing page and on our garage conversion cost guide and ADU cost guide.

Cost: the garage is a head start, not a discount

A two-car garage conversion at $100,000 to $200,000 against a 500-square-foot detached ADU at $180,000 to $260,000 looks like a clear win for the conversion, and on a sound garage it is. The savings are specific: no foundation, no framing, no roof, no solar array. What you still pay for is everything that makes a garage a home, and a 400-square-foot ADU contains the two most expensive rooms in any house, a kitchen and a full bathroom. A $100,000 to $150,000 conversion of a 400-square-foot garage works out to roughly $250 to $375 per square foot, below the $300 to $450 we publish for new construction; but the ranges overlap, because a detached garage at the back of a deep Valley lot with a cracked slab, a 100-amp panel and a clay sewer lateral can cost as much as a small new unit. What moves either number is the same short list: slab or foundation, the sewer run and the lateral’s condition, the 200-amp service upgrade most 1950s to 1970s houses need, the envelope, and the kitchen and bathroom, which cost the same on both routes. Our garage conversion cost guide itemizes each.

Two real projects, one from each side

The conversion that rose 40 percent. In why ADU quotes vary so much between contractors, a homeowner converting a detached two-car garage of roughly 400 square feet into a one-bedroom ADU with a kitchen, bathroom and laundry started with an estimate of $85,000 to $95,000. Three discoveries moved it to about $130,000: the slab had no proper moisture barrier and needed preparation and concrete work; the home’s original 100-amp panel had to become 200 amps; and a camera inspection found root intrusion and bellying in the sewer, so a section had to be replaced before the new fixtures could connect. None of that was a luxury; each was a condition the garage already had.

The detached unit that went from $180,000 to $265,000. In our ADU cost guide, homeowners who had already removed an old, deteriorated garage planned a roughly 600-square-foot one-bedroom detached ADU on a budget of about $180,000; it finished near $265,000 after a $14,000 clay sewer reroute under the new foundation, a $6,000 to $8,000 panel upgrade with about three weeks of utility delay, and about $30,000 of finish upgrades chosen after framing. It is also the third option this guide keeps coming back to: when the garage is too far gone to convert, demolish it and build new on the same spot.

A finished conversion. Our garage-to-ADU conversion in Los Angeles, completed in 2025, started as a plain stucco box of about 500 square feet with one wide door opening and a single small window and became a self-contained rental with a rebuilt roof structure, new framing and sheathing, new windows and French doors, matched stucco, a full kitchen with an island and a full bathroom with a tiled shower. Notice that the roof structure was rebuilt, which is common once an old garage roof is asked to carry insulation, drywall and a ceiling.

The rules: where each one is allowed

California’s ADU statute lives in Government Code sections 66310 to 66342, and the rules below are verified against it and against LADBS; sources are at the end.

Conversions: no setback, no replacement parking, no separate connection

A garage converted to an ADU within its existing footprint needs no setback; section 66314(d)(7) says none shall be required for “an existing living area or accessory structure or a structure constructed in the same location and to the same dimensions as an existing structure” that is converted, and section 66323(a)(1) lets the unit expand up to 150 square feet for entry and exit. A garage one foot off the rear property line can become an ADU where a new building could not, provided the wall assembly handles fire separation. When a garage, carport or covered parking is converted or demolished for an ADU, section 66314(d)(11) says the city “shall not require that those offstreet parking spaces be replaced”; LADBS puts it plainly: “If you remove covered parking to build an ADU, you don’t need to replace it.” For an ADU within existing space, section 66311.5 (formerly 66324) bars the city or the utility from requiring a new or separate utility connection unless the unit is built with a new house. Sprinklers follow the main house on both routes.

Detached: 800 square feet guaranteed, four-foot setbacks, height, solar

For a new detached unit, section 66323(a)(2) requires ministerial approval of one detached ADU of up to 800 square feet with four-foot side and rear setbacks, and section 66321 bars a city from applying any floor-area, lot-coverage or open-space standard that would prevent it. Height is at least 16 feet, or 18 feet within half a mile walking distance of a major transit stop, and under the City of Los Angeles ordinance a detached ADU can go to 1,200 square feet where the lot’s own standards allow; our Los Angeles ADU rules page and ADU rules calculator show what applies to your project. LADBS states that “detached ADUs built from scratch must have solar panels,” a state energy-code requirement a conversion does not carry. An ADU of 750 square feet or less is exempt from local impact fees on either route.

Standard plans and the 60-day clock

The LADBS ADU Standard Plan Program pre-approves complete designs for detached units, roughly 60 plans from 200 to 1,200 square feet including the city-owned YOU-ADU plan that owners may use free of charge, and plan check is then limited to site-specific items such as zoning and the foundation. A conversion starts from the garage you already have, so it goes through regular plan check with its own drawings; our guide to ADU standard plans in Los Angeles explains when the catalog helps. Both routes get the same deadline under section 66317: the city must confirm within 15 business days that an application is complete and approve or deny it within 60 days, or it is deemed approved, with no hearing or neighbor notice.

What a garage conversion cannot fix

This is what decides most projects, and it is why the site walk comes before the price. Los Angeles County Building and Safety publishes standard notes for converting an existing single-story garage, and the same state building code applies inside the City of Los Angeles and in every other city we work in. Some of what those notes require can be fixed with money; some cannot be fixed at all.

• Ceiling height. Habitable rooms need a ceiling of at least 7 feet (California Residential Code R305.1). Most garages clear it at the plate but not always once a finished ceiling, insulation and a level floor go in. Raising the roof is possible, as on the 2025 project above, but at that point you are paying for framing and a roof anyway.
• Slab elevation and condition. The garage slab was poured to hold a car: it slopes toward the door, often sits below the house’s finished floor, and on older garages has no vapor barrier. The County notes allow a sound 3-inch slab as is and a sound 2-inch slab only with a 2-inch concrete topping, with an approved moisture barrier over it; a cracked, heaved or thin slab gets replaced. What cannot change is where the slab sits relative to the yard and the house, which fixes the floor level, the drainage and the step at the door.
• Footings. A garage’s continuous footing was sized for a garage. The County requires the pre-construction meeting to include “exposing a section of the foundation to verify existing footing depth” for the added anchoring and bracing, and the garage-door opening “shall be converted to a permanent wall and a new foundation at this location shall be installed and anchored to the existing continuous footing.” If the footing turns out to be shallow or broken, the conversion becomes a partial rebuild.
• Footprint and position. The unit sits where the garage sits, at the garage’s size plus 150 square feet. If the garage is 300 square feet or backs onto the neighbor’s bedroom, no design fixes that.
• Envelope and openings. Walls, roof and floor have to reach the residential energy standard (R-21 in 2×6 or R-15 in 2×4 walls in the County notes), a bedroom needs an egress window of 5.7 square feet net clear opening, and the unit needs light and ventilation openings a garage never had. On an attached garage the wall to the house becomes a one-hour fire-rated assembly from slab to roof sheathing.
• Sewer. The drain has to reach the lateral with fall; the County notes call for the connection at least 24 inches outside the existing foundation at a 2 percent slope. A garage downhill from the sewer, or far from it, means a pump or a long trench.

None of this means conversions are a bad idea. It means the garage has to be looked at before it is priced, and the honest outcome of a site walk is sometimes “demolish and build new on the same footprint,” which keeps the no-setback benefit while solving the height, slab and footing problems at once. For a smaller unit inside the existing house, see our guide to junior ADU rules and cost in Los Angeles.

Rent and value: what each one is worth

Tenants pay for a kitchen, a bathroom, light and privacy, not for how the building started, so a properly done conversion tends to rent like a detached unit of the same size, and a compromised one (low ceiling, small windows, a step down at the door) tends to rent for less. A larger detached unit with a second bedroom rents for more than any two-car garage can, and it can be placed for privacy from the main house in a way a garage on the driveway cannot. We do not publish rent figures because they vary by neighborhood; HUD’s Fair Market Rents for Los Angeles County are a conservative benchmark, and our ADU financing guide shows how to compare net rent with the loan payment. On property tax, both routes are treated the same way: the county assessor values the new construction as of completion and adds only that amount, and the existing house is not reassessed. At resale, either unit sells with the house as a property with an income unit; a conversion also removes covered parking, which some buyers care about more than others.

When each one wins

Convert the garage when it is structurally sound, with a good slab, adequate ceiling height and a roof worth keeping; its size and position already suit a studio or one-bedroom of about 400 square feet; the lot has no room for a new building four feet off the lines, or the yard matters more to you than the garage; budget is the constraint and $100,000 to $200,000 is the number you can finance; or you want the shorter schedule.

Build a detached ADU when you want two bedrooms, higher ceilings or a unit over 550 square feet; the garage is too low, too small, badly placed or in poor condition, so a conversion would need a new roof, slab and footings anyway; you want to keep the garage for parking and storage; the lot is deep enough for a private unit away from the house; or rental value is the goal and a larger unit will carry the higher cost.

Demolish and rebuild on the garage footprint when the garage is in the right place but the wrong condition; a structure “constructed in the same location and to the same dimensions” keeps the no-setback benefit.

Answer a few questions in the ADU rules calculator before you decide, and expect the site walk to check the slab, the ceiling, the footings, the panel and the sewer before any number is written.

Where we do this work

The choice between converting and building new shifts with the housing stock. Across the San Fernando Valley and the City of Los Angeles, 1950s to 1970s ranch houses come with detached two-car garages at the back of the lot that convert well when the slab and roof are sound, LADBS reviews both routes, and the standard plan catalog is available for detached units; see four ways to add an ADU in Los Angeles. In Orange County, attached garages on 1970s to 1990s tract houses are common, HOA review applies to either project, and keeping covered parking often tips the decision toward a detached unit. Ventura County cities such as Thousand Oaks and Simi Valley run their own building divisions, and hillside lots often need a soils report for a new foundation. In western Riverside County and western San Bernardino County, the larger lots of Corona, Ontario and Rancho Cucamonga make both routes feasible, and expansive soils can call for a geotechnical report on a detached unit; as our Corona ADU page explains, the attached garages and HOAs of Corona’s newer tracts change the calculus there. See all of our service areas.

Sources

ADU law changes most years and local ordinances are amended separately from the state statute. The rules referenced above were checked against the current state sources on the date shown; confirm anything decision-critical with LADBS or your city for your specific lot.

• California Department of Housing and Community Development, Housing Law Fact Sheets — Accessory Dwelling Units (April 2026) — confirms that ADU law sits at Government Code sections 66310–66342, the four-foot side and rear setback limit for new detached ADUs, the 60-day decision deadline, and that impact fees may not be charged on an ADU of 750 square feet or less or on a JADU.
• California HCD, Accessory Dwelling Unit Handbook (March 2026) — Government Code section 66321(b)(3) bars a city from applying lot coverage, floor area ratio, open space or minimum lot size standards that would not permit at least an 800 square foot ADU with four-foot side and rear setbacks, at a height of up to 16 feet.

Last reviewed 17 September 2026.

Detached ADU vs. garage conversion FAQs

Is it cheaper to convert a garage or build a detached ADU?

Converting a garage is usually cheaper: a garage conversion ADU in Los Angeles typically runs $100,000 to $200,000, while a detached ADU runs $180,000 to $260,000 for about 500 square feet and $300,000 to $450,000 or more for about 1,000 square feet. The gap narrows when the garage needs a new slab, footings or roof. These are typical Los Angeles budgeting estimates, not a price list or a quote; a real project can come in lower or higher.

Do I have to replace the parking if I convert my garage into an ADU?

No. Under California Government Code section 66314(d)(11), when a garage, carport or covered parking structure is converted to an ADU or demolished to build one, the city cannot require the lost off-street parking spaces to be replaced, and LADBS states the same rule for the City of Los Angeles. A detached ADU that leaves the garage standing keeps your covered parking.

Does a garage conversion ADU need setbacks?

No. A garage converted to an ADU within its existing footprint, or rebuilt to the same dimensions in the same location, needs no setback under Government Code section 66314(d)(7), and it may add up to 150 square feet for entry and exit under section 66323. A new detached ADU must sit at least four feet from the side and rear property lines. This is why a garage on the property line can become an ADU where a new building could not.

What can’t a garage conversion fix?

A garage conversion cannot change the slab’s elevation, the footprint’s size beyond 150 square feet of expansion, or its position on the lot, and it inherits the original footings and ceiling height. Habitable rooms need a ceiling of at least 7 feet, the garage-door opening must get a new foundation tied to the existing footing, and a thin or cracked slab needs topping or replacement. When those add up, demolishing and rebuilding on the same footprint keeps the no-setback benefit and solves all of them.

Does a detached ADU need solar panels?

Yes. LADBS states that detached ADUs built from scratch must have solar panels under the California energy code, while a garage conversion ADU does not carry that requirement because it is a conversion of an existing structure. The solar system is one of the items that makes a detached unit cost more than a conversion, alongside the new foundation, framing and roof.

Can I use an LADBS standard plan for a garage conversion?

No. The LADBS ADU Standard Plan Program pre-approves complete designs for new detached ADUs, so plan check is limited to site-specific review of zoning and foundation; a garage conversion starts from the garage you already have and goes through regular plan check with its own drawings. Both routes are covered by the state’s 60-day approval deadline for a complete application.

Convert it, rebuild it, or build new? Let us look at the garage first.

We will measure the ceiling, check the slab and expose the footing if needed, camera the sewer, check the panel and the setbacks, and tell you in writing whether your garage is worth converting, with a budgeting range for each route. The site visit and the estimate are free.

A room addition makes the house you live in bigger; an accessory dwelling unit (ADU) is a separate, self-contained home with its own kitchen, bathroom and entrance that can be rented, house a relative, or sit empty until you need it. In Los Angeles the two cost about the same per square foot, but they are governed by different rules, take different amounts of time, and answer different questions: an addition is the right choice when the new space must connect to your existing rooms, and an ADU is the right choice when you want income, independence for the occupant, or square footage your lot’s zoning would not otherwise allow. Green Design and Build is a licensed general contractor (CSLB #1110975) based in Van Nuys that designs and builds both, for homeowners across Los Angeles County, Orange County, Ventura County, western Riverside County and western San Bernardino County (Ontario, Rancho Cucamonga and neighboring cities).

We are led by Dekel Sofer. We hold a 4.7-star rating across 146 Yelp reviews and have completed hundreds of projects across all five counties. Because we build room additions and ADUs with the same team, we have no reason to steer you toward one; the first job on a site walk is telling you which one your lot and your goal actually call for.

ADU vs. room addition at a glance

These are typical Los Angeles budgeting estimates, not a price list or a quote. Your project can come in lower or higher depending on the house, the scope and the finishes; the only real number is a written proposal after a site visit. The addition figures are from our room addition cost guide and the ADU figures from our ADU cost guide.

Cost: close per square foot, different in total

Per square foot the two are close: $300 to $500 all-in for a ground-floor addition, $300 to $450 for a detached ADU, and past $500 for either on a difficult lot. The total is where they separate, because they are rarely the same size.

These are typical Los Angeles budgeting estimates, not a price list or a quote. Your project can come in lower or higher depending on the house, the scope and the finishes; the only real number is a written proposal after a site visit.

An ADU always contains the two most expensive rooms in any house, a kitchen and a full bathroom, so a 400-square-foot ADU carries more plumbing, electrical and cabinetry than a 400-square-foot family room. On the other hand, a garage conversion starts with a slab, walls and a roof, which is why it sits at the bottom of every ADU range, and a detached unit does not disturb the house you live in, so there is no cost for tying a new roof into an old one or opening a bearing wall. A second-story addition is the most expensive space per square foot because the roof comes off and the framing below often has to be strengthened to carry it.

On either project, hold a contingency of 15 to 20 percent above the accepted bid, especially on a pre-1980 house. The 600-square-foot detached ADU retold in our ADU cost guide went from a $180,000 budget to about $265,000 after a clay sewer line under the new foundation had to be rerouted (about $14,000), the 100-amp panel became 200 amps ($6,000 to $8,000 and about three weeks waiting on the utility), and the owners added roughly $30,000 of finish upgrades. Every one of those can happen on an addition.

Rules: the ADU can go where the addition cannot

This is the difference that decides more projects than cost does.

The addition has to fit the zoning

In the City of Los Angeles, which includes most of the San Fernando Valley, a room addition on a typical R1 lot has to sit inside the lot’s setbacks, usually 20 feet or the prevailing setback at the front, 5 feet from each side property line and 15 feet from the rear, and under the Baseline Mansionization Ordinance’s cap on total floor area, 45 percent of the lot area on most R1 lots. A 1,500-square-foot house on a 6,000-square-foot lot is at 25 percent and has room; a 2,700-square-foot house on the same lot is at the limit and cannot add a room, regardless of what the yard looks like. Every addition goes through full plan check with plumbing, electrical and mechanical permits; an addition in a Historic Preservation Overlay Zone goes through the Office of Historic Resources, and hillside lots add grading review and usually a geotechnical report. Our room additions page walks through these rules.

The ADU is protected by state law

California Government Code section 66323 requires the city to approve, ministerially, one detached new-construction ADU of up to 800 square feet with four-foot side and rear setbacks on a lot with a single-family home, and section 66321 bars a city from applying any development standard, including floor-area ratio and lot coverage, that would prevent it. Height is at least 16 feet for a detached unit, 18 feet within half a mile walking distance of a major transit stop, and up to 25 feet or the zone’s limit for an attached unit; under the City of Los Angeles ordinance a detached ADU can go to 1,200 square feet where the lot’s own standards allow. A garage converted to an ADU needs no setback at all, and the city cannot require replacement parking. On a lot at its 45 percent limit, the ADU is the only new square footage available. Answer a few questions in our ADU rules calculator or read the Los Angeles ADU rules page.

The permit clock

Section 66317 requires the city to tell you within 15 business days whether an ADU application is complete and to approve or deny a complete application within 60 days; if it does neither, “the application shall be deemed approved.” There is no equivalent deadline for a room addition, which is why plan check for an addition runs two to four months in our published timeline and a complete ADU submittal is usually through faster. Both wait on the same utility clearances.

Attached ADU versus addition: the gray area

An attached ADU is physically an addition with its own entrance, kitchen and bath, and a wall between it and the house. State law caps it at 50 percent of the existing house’s floor area, with an 800-square-foot floor the city must allow, and lets it rise to 25 feet or the zone height limit, whichever is lower. Homeowners who want a suite for a parent today and a rental in ten years often build an attached ADU rather than a primary-suite addition; the kitchen and the separate entrance are what make the space rentable later, and the cost of the kitchen is the price of that option.

Timeline: 9–14 months versus 6–12 months

Our published schedule for a room addition is 9 to 14 months from first meeting to final inspection: 6 to 10 weeks of design, engineering and Title 24 for a ground-floor addition (8 to 12 for a second story), 2 to 4 months of plan check, and 4 to 7 months of construction (5 to 7 for a second story). An ADU runs 6 months to a year, garage conversions at the short end and large detached units at the long end; our guide to how long an ADU takes breaks it down phase by phase.

The gap comes from two places. Plan check is shorter for an ADU because of the 60-day rule, and in the City of Los Angeles a detached unit can use one of the LADBS pre-approved standard plans, which limits plan check to site-specific items. Construction is also usually shorter for a detached ADU than for an addition of the same size because the crew is not working inside an occupied house: no protecting the existing rooms, no tying into a kitchen in use, no roof open over the family. A second-story addition is the extreme case, where the house is often unlivable for part of the build.

Rent, family and resale: what each one is for

An addition is used by the people who own the house, and its value at resale is the value of a larger house on that street; a primary suite or family room in a 1,200-square-foot Valley ranch house tends to bring it in line with the larger homes nearby, but it produces no income. An ADU is a separate dwelling: it can be rented long term (state law bars a city from requiring owner occupancy for a standard ADU, and rentals of state-exemption ADUs and junior ADUs must be longer than 30 days), it can house a parent with a real front door between the generations, and it can revert to family use later. At resale it is marketed as a property with an income unit, but it stays part of the same parcel; state law only lets an ADU be sold separately as a condominium where the city has adopted an ordinance under Government Code section 66342.

The property-tax treatment is the same for both: new construction is assessed at market value when completed and added as a supplemental assessment, and the existing house and land are not reassessed, so your Proposition 13 base stays where it is. Rent is the factor we will not put a number on; HUD’s Fair Market Rents for Los Angeles County and a local property manager are the right sources, and our ADU financing guide shows how to compare net rent against the loan payment.

How to decide

Work through these in order; most homeowners have an answer by the third question.

If an addition is the direction, home addition ideas for a Los Angeles house walks through bump-outs, primary suites, family room expansions and partial and full second stories, with a cost range for each.

1. Does the new space have to open into the rooms you already have? A bigger kitchen, a family room off the living room, a second bathroom for the kids’ bedrooms: addition. Space used by someone else, or by you with a door between it and the house: ADU.
2. Do you want income, now or later? If yes, ADU; an addition never pays rent. If the answer is “maybe in ten years,” an attached ADU or a detached unit with a real kitchen keeps the option.
3. Is the lot at its floor-area limit or short on setbacks? If an addition does not fit under the 45 percent cap and the setbacks, the 800-square-foot ADU exemption is the square footage the state guarantees you.
4. Is there a garage you do not need for cars? A two-car garage of about 400 square feet is the lowest-cost route to an ADU, and the city cannot make you replace the parking. If you want the garage as part of the house instead, that is an addition and follows the addition rules.
5. Who is going to live in it? A parent who needs a bedroom near the family: addition or junior ADU inside the house. A parent who wants independence, an adult child, or a tenant: separate unit.
6. Can you live in the house during construction? An ADU does not disturb the house; a second-story addition is the slowest and most disruptive option and often means moving out for part of the build.
7. What will the neighborhood pay for? On a street of 2,500-square-foot houses, taking a 1,300-square-foot house to 2,000 is value the market recognizes. On a street of small houses on large lots near transit, an income unit is what buyers pay for.

Can you do both?

Yes, and on many lots it is the right answer. State law allows a detached ADU of up to 800 square feet regardless of the lot’s floor-area cap, and a junior ADU of up to 500 square feet inside the house alongside it, so a homeowner can add a primary suite under the zoning rules and still build a detached unit in the yard under the ADU rules. One design and engineering package that covers both saves a second round of plan check, and the 200-amp panel and any sewer repair get sized once for the whole property. A common Valley plan is a garage conversion ADU now and a second-story addition later, once the rent is coming in; another is an attached ADU built as the parents’ suite with a detached rental behind it.

Where we do this work

The rules that decide between an ADU and an addition change with the address. Inside the City of Los Angeles and most of the San Fernando Valley, the 45 percent floor-area cap and the R1 setbacks apply to additions and LADBS reviews both projects, with the standard plan catalog available for detached ADUs. In Orange County, each city sets its own floor-area and setback rules, and master-planned communities in Irvine and Anaheim Hills add HOA review, though state law voids covenants that prohibit or unreasonably restrict an ADU; our Anaheim ADU page covers the Anaheim Hills case, where slope, a soils report and usually an HOA come together. Ventura County cities such as Thousand Oaks have their own building divisions and hillside lots that often need a soils report; in Thousand Oaks, whether the lot is flat and whether it sits in a fire zone decide most of an ADU’s cost, as our ADU page for Thousand Oaks explains. In western Riverside County and western San Bernardino County, larger lots in Corona, Ontario and Rancho Cucamonga make a detached ADU and a ground-floor addition both feasible, and expansive soils can call for a geotechnical report. See all of our service areas.

ADU vs. room addition FAQs

Is an ADU cheaper than a room addition?

Per square foot they are close in Los Angeles: a ground-floor room addition typically runs $300 to $500 per square foot all-in and a detached ADU $300 to $450, while a second-story addition runs $400 to $650. In total an ADU often costs more than an addition of the same size because it always includes a kitchen and a full bathroom, and a garage conversion ADU at $100,000 to $200,000 is usually the lowest-cost route to a separate unit. These are typical Los Angeles budgeting estimates, not a price list or a quote; a real project can come in lower or higher.

Can I build an ADU if my lot is at its floor-area limit?

Yes. California Government Code sections 66321 and 66323 require a city to approve a detached ADU of up to 800 square feet with four-foot side and rear setbacks even where the lot’s floor-area ratio or lot coverage would block an addition of the same size. In the City of Los Angeles, a lot at the 45 percent Baseline Mansionization limit cannot add a room, but it can still build that ADU. Our ADU rules calculator shows what applies to your project.

Which adds more value, an ADU or an addition?

It depends on the street and the buyer. A room addition raises the value of the house toward the larger homes nearby; an ADU adds a separate dwelling that can produce rent and is marketed as a property with an income unit. Neither triggers a reassessment of your existing house; the county assessor adds only the value of the new construction. We do not publish value or rent figures because they vary by neighborhood; an appraiser or agent who knows your street is the right source.

How long does an ADU take compared with a room addition?

An ADU in Los Angeles typically takes six months to a year from first meeting to move-in, and a room addition 9 to 14 months. The ADU is faster because state law requires the city to approve or deny a complete ADU application within 60 days and because construction does not disturb the occupied house, while plan check for an addition runs two to four months and a second-story addition can take five to seven months of construction alone.

Can I do a room addition and an ADU on the same lot?

Yes. The floor-area cap applies to the addition, and the state’s 800-square-foot ADU exemption applies to the ADU, so a homeowner can add a primary suite to the house and still build a detached unit in the yard, with a junior ADU of up to 500 square feet inside the house also allowed. Designing both on one set of drawings saves a second plan check and lets the panel upgrade and any sewer work be sized once for the whole property.

What is the difference between an attached ADU and a room addition?

An attached ADU is an addition with its own entrance, kitchen and bathroom, separated from the house by a wall, and it can be rented as a separate dwelling; a room addition opens into the existing house and is part of it. State law caps an attached ADU at 50 percent of the existing house’s floor area, with an 800-square-foot floor the city must allow, and lets it rise to 25 feet or the zone height limit. Homeowners who may want rental income later often choose the attached ADU and pay for the kitchen that makes it rentable.

Sources

The ADU rules on this page are California statute, which the Legislature amends most years; local ordinances are updated separately and can lag it. Room additions are governed by ordinary zoning and building code instead, which varies by city. Confirm both before you choose between them.

• California HCD, Housing Law Fact Sheets — Accessory Dwelling Units — ADU law at Government Code sections 66310–66342: the 60-day decision deadline, four-foot side and rear setbacks, and no impact fees on an ADU of 750 sq ft or less.
• California HCD, Accessory Dwelling Unit Handbook (March 2026) — Government Code section 66321(b)(3), the rule that local standards may not prevent at least an 800 sq ft ADU with four-foot setbacks at up to 16 feet.
• LADBS, Building Permits — the work that requires a permit in the City of Los Angeles, and the rule that building plans must be approved as a Building Plan Check before a permit is issued.

Last reviewed 17 September 2026.

Not sure whether your lot wants an ADU or an addition? Walk it with us.

We will check your setbacks and floor-area limit, camera the sewer, look at the panel and the garage, and tell you in writing which project fits your lot and your goal, with a budgeting range for each. The site visit and the estimate are free.

Most homeowners in Los Angeles finance an ADU with home equity: a home equity line of credit (HELOC), a home equity loan, or a cash-out refinance, and those who do not have the equity yet use a renovation loan or a construction loan that lends against the value of the property with the ADU finished. Green Design and Build is a licensed general contractor (CSLB #1110975) based in Van Nuys, not a lender; we build detached ADUs, garage conversions, attached ADUs and junior ADUs for homeowners across Los Angeles County, Orange County, Ventura County, western Riverside County and western San Bernardino County (Ontario, Rancho Cucamonga and neighboring cities), and this guide explains the financing paths Los Angeles homeowners use so you know what to ask a lender for. Our published Los Angeles budgeting estimates run from $100,000 to $200,000 for a garage conversion ADU to $300,000 to $450,000 or more for a 1,000-square-foot detached unit; these are typical budgeting estimates, not a price list or a quote, and your project can come in lower or higher.

We are led by Dekel Sofer. We hold a 4.7-star rating across 146 Yelp reviews and have completed hundreds of projects across all five counties. Green Design and Build offers financing programs through Synchrony, Service Finance and Home Run Financing; terms depend on the lender and credit approval, and the details are on our financing page.

How much are you financing?

The loan has to fit the project, so start with the number. The ranges below are the ones published on our pricing page and on our ADU cost guide.

These are typical Los Angeles budgeting estimates, not a price list or a quote. Your project can come in lower or higher depending on the house, the scope and the finishes; the only real number is a written proposal after a site visit.

Two adjustments matter for the loan amount. First, our ADU cost guide recommends a contingency of 15 to 20 percent above the accepted bid; on the 600-square-foot detached ADU retold there, a $180,000 budget finished near $265,000; the largest items were a $14,000 sewer reroute, a $6,000 to $8,000 panel upgrade and about $30,000 of finish upgrades the owners chose after framing. Borrow the contingency up front; a HELOC you do not draw costs little, and a second loan mid-project costs time. Second, include the soft costs that come before construction: design, engineering, Title 24, plan check and permit fees, and any soils report. Our post on why ADU quotes vary so much between contractors explains what a complete quote includes, and our pricing page collects every range we publish.

ADU financing options compared

Which one is right depends on your equity, your existing mortgage rate, your income and how fast you need the funds. We describe how each works below without rates, because rates change and lenders differ.

HELOC

A HELOC is the financing path homeowners use most often for an ADU because it matches how a construction contract is paid: in stages. You draw against the line as each progress payment comes due and pay interest only on what you have drawn. The lender sets the line as a percentage of your home’s appraised value minus your first mortgage, so an owner of a 1960s Valley house bought a decade ago usually has room; an owner who bought in the last two years may not. Most HELOCs carry a variable rate and a draw period followed by a repayment period, so ask what the payment looks like once the draw period ends.

Home equity loan

A home equity loan is a second mortgage for a fixed amount at a fixed rate, funded in a lump sum. It suits an owner who wants a payment that does not move and a budget already settled by a site walk and a written proposal. The trade-off is interest on the full amount from closing, including money that sits in the bank for months waiting for plan check.

Cash-out refinance

A cash-out refinance replaces your existing mortgage with a larger one and hands you the difference. It only makes sense when the new rate is close to the one you have; an owner with a low-rate mortgage from a few years ago usually keeps it and adds a second lien instead. It does give you one payment and a fixed rate on the whole balance.

Renovation loans: FHA 203(k) and Fannie Mae HomeStyle Renovation

Renovation loans are the route for homeowners who do not have the equity today but will once the ADU exists, because the lender underwrites against the as-completed appraised value. The FHA 203(k) program lets homebuyers and homeowners finance repairs and improvements into the mortgage; the Limited 203(k) is capped at $75,000 of improvement cost, so an ADU usually needs the Standard 203(k). Since October 2023, FHA has allowed lenders, for some borrowers, to count 50 percent of the estimated rental income from a new ADU the borrower plans to add under a Standard 203(k) toward qualifying, and 75 percent of the estimated rent from an existing ADU. Fannie Mae’s HomeStyle Renovation mortgage lets a borrower “purchase a property or refinance an existing loan and include funds in the loan amount to cover the costs of repairs, remodeling, renovations, or energy improvements,” and Fannie Mae’s guide states it may be used to construct accessory units where local zoning allows. Both programs require plans, a contractor the lender accepts and a cost breakdown before closing, and both pay the contractor through lender-controlled draws with inspections. Ask the lender specifically whether the loan can be used for a detached ADU on your lot and how ADU rental income is treated in qualifying; the rules differ by program and lender.

Construction loans

A construction loan funds the build in draws tied to completed work, with interest-only payments during construction, and usually converts to a permanent mortgage when the ADU is finished. It is the tool for a larger detached unit when equity will not cover the budget and a renovation loan does not fit. Expect the lender to require the full plan set, the building permit, our written proposal and schedule, and an inspection before each draw, so design and permitting should be well along before you apply; our guide to how long an ADU takes shows where in the calendar that is.

Personal loans and contractor financing

Unsecured personal loans close fast and put no lien on the house, but the amounts and terms rarely fit a full ADU budget; they are more often used for a contingency or the last stretch of a phased project. Green Design and Build offers financing programs through Synchrony, Service Finance and Home Run Financing; terms depend on the lender and credit approval. We do not set the rates and we cannot promise approval.

Cash

Paying cash avoids interest and closing costs, but it removes the discipline a lender’s draw schedule imposes. Keep the 15 to 20 percent contingency in a separate account and pay on the same milestone schedule you would with a lender.

How the contract and the draw schedule shape your payments

Whatever loan you use, California law fixes the shape of the payments. Under Business and Professions Code section 7159, a home improvement contract must state that “the downpayment may not exceed $1,000 or 10 percent of the contract price, whichever is less,” and that “it is against the law for a contractor to collect payment for work not yet completed, or for materials not yet delivered.” Change orders become part of the contract only when written and signed by both parties before the work starts. So a legitimate ADU contract in Los Angeles has a small deposit, progress payments tied to milestones such as foundation, framing, rough inspections, drywall and final, and written change orders for anything discovered along the way.

For financing, three things follow:

1. Your loan has to fund in stages. A HELOC or a construction loan does that natively. A home equity loan or cash-out refinance funds once, so the money sits until each milestone; a renovation loan funds through the lender’s own draw process, which you and we both follow.
2. Milestones drive interest. On a HELOC, a project that finishes in seven months costs less interest than the same project at twelve; on a lump-sum loan the interest clock runs regardless. Read the schedule in our ADU timeline guide with the loan in hand.
3. Change orders need funded money behind them. On the $180,000 project that finished at $265,000, every increase was a written change order for a real condition or a real upgrade. An owner with the contingency in the HELOC approves a change order in a day; an owner who has to go back to the lender waits, and the crew waits with them.

Does the rent pay for the loan?

For a rental ADU the question is whether the rent covers the payment. The honest way to answer it is arithmetic with your own lender’s payment figure, not a number from a contractor’s brochure. Our ADU rental income guide puts HUD’s FY 2026 Fair Market Rents for each county against typical build costs.

• Start with realistic rent. The U.S. Department of Housing and Urban Development publishes Fair Market Rents for Los Angeles County by bedroom count each year (see HUD’s Fair Market Rents); those figures are a conservative floor for a new studio or one-bedroom, and a local property manager will give you a market figure for your neighborhood.
• Subtract what the tenant does not pay. Vacancy, the ADU’s share of property tax, insurance, maintenance and any utilities you keep in your name. Most ADUs share the house’s water, sewer and panel, so decide early whether you want a separate electric meter for the tenant.
• Compare net rent to the loan payment. If net monthly rent covers the payment on the loan you actually used, the unit carries itself; if not, the gap is the price of the space, the family use or the long-term value.
• Count the property-tax change correctly. Building an ADU in California does not trigger a reassessment of the existing house; the county assessor values the new construction as of completion and adds only that amount as a supplemental assessment, so your Proposition 13 base on the main house stays where it is.
• Ask about rental income in qualifying. Some FHA and conventional programs let a lender count a portion of projected or existing ADU rent toward your income; the percentages and conditions differ by program, so raise it in the first conversation.

State law bars a city from requiring owner occupancy for a standard ADU, and rentals of state-exemption ADUs and JADUs must be for terms longer than 30 days, so plan on a lease rather than a short-term rental.

What lenders will ask us for

Every lender that funds construction wants the same package, and we prepare it as part of the project: a written feasibility summary from the site walk with the budgeting range; the plan set, engineering and building permit; an itemized proposal with allowances, exclusions, the progress-payment schedule and the change-order procedure required by section 7159; our license, bond and insurance details (verify CSLB #1110975 on the CSLB site); and a construction schedule with milestones the lender can tie draws to. Renovation and construction lenders may also require lien releases at each draw and an inspection before funds are released.

Choosing the right ADU financing

• Plenty of equity and a low existing mortgage rate: HELOC, or a home equity loan if you want a fixed payment.
• Existing rate close to today’s rates: compare a cash-out refinance against a HELOC on total cost, not just the rate.
• Thin equity but a property that will appraise well when finished: a renovation loan (Standard 203(k) or HomeStyle Renovation) or a construction loan; if you are buying the house now, a renovation loan at purchase covers both in one closing.
• Most of the money and a small gap: contractor financing or a personal loan for the gap.
• Unsure the unit pencils out: do the rent arithmetic above first, and consider a garage conversion at the bottom of the budget range before a detached unit at the top.

We are a builder, not a lender or a financial adviser, and the right loan depends on facts about your finances we do not see. Talk to at least two lenders, bring our feasibility summary, and ask each for the total cost of the loan over the life of the project, not the rate alone.

Where we do this work

Financing an ADU works the same across our service area; the budget it has to cover does not. Inside the City of Los Angeles and the San Fernando Valley, a detached unit can use an LADBS pre-approved standard plan and older Valley houses usually need the 200-amp panel upgrade in the budget. In Orange County and Ventura County, each city runs its own building division and HOA review in master-planned communities adds time, so a HELOC in place before design starts avoids paying interest on idle money. In western Riverside County and western San Bernardino County, newer houses in Corona, Ontario and Rancho Cucamonga tend to have larger lots and 200-amp service already, which keeps a detached unit nearer the bottom of its range. See all of our service areas.

ADU financing FAQs

How much does it cost to build an ADU in Los Angeles?

A garage conversion ADU in Los Angeles typically runs $100,000 to $200,000, a detached ADU of about 500 square feet $180,000 to $260,000, and a detached unit of about 1,000 square feet $300,000 to $450,000 or more, with new construction at roughly $300 to $450 per square foot all-in. These are typical Los Angeles budgeting estimates, not a price list or a quote; a real project can come in lower or higher, and the only real number is a written proposal after a site visit.

What is the best way to finance an ADU?

For most Los Angeles homeowners with equity, a HELOC is the best fit for financing an ADU because you draw funds as each progress payment comes due and pay interest only on what you have used. A home equity loan or cash-out refinance suits owners who want a fixed payment, and a renovation or construction loan suits owners whose equity will not cover the budget until the ADU is finished. The right choice depends on your equity, your existing mortgage rate and your income, so compare at least two lenders.

Can I use an FHA 203(k) loan to build an ADU?

Yes, an FHA Standard 203(k) loan can finance an ADU as part of a purchase or refinance, with the improvement cost included in the mortgage; the Limited 203(k) is capped at $75,000 of improvements, which is below most ADU budgets. Since October 2023, FHA has let lenders count, for some borrowers, 50 percent of the estimated rental income from a new ADU built under a Standard 203(k) toward qualifying. The lender approves the plans and the contractor before closing and pays for the work through inspected draws.

Does Green Design and Build offer financing for ADUs?

Green Design and Build offers financing programs through Synchrony, Service Finance and Home Run Financing; terms depend on the lender and your credit approval. We are a builder, not a lender, so we cannot promise approval or quote a rate. For a full ADU budget most homeowners use home equity, a renovation loan or a construction loan, and we provide the feasibility summary, plans, proposal and schedule those lenders require.

How much can I put down on an ADU contract in California?

Under California Business and Professions Code section 7159, the down payment on a home improvement contract may not exceed $1,000 or 10 percent of the contract price, whichever is less, and a contractor may not collect payment for work not yet completed or materials not yet delivered. The rest of an ADU contract is paid in progress payments tied to milestones, which is why a loan that funds in stages, such as a HELOC or construction loan, matches the contract well.

Will building an ADU raise my property taxes?

Building an ADU in California adds the assessed value of the new construction to your property tax bill but does not trigger a reassessment of your existing house and land, so your Proposition 13 base on the main home stays where it is. The county assessor values the ADU as of completion and bills the difference as a supplemental assessment. The Los Angeles County Assessor publishes ADU guidance and can estimate the effect for your project.

Get the numbers your lender will ask for

Before you apply for anything, we will walk your lot, camera the sewer, check the panel and give you a written feasibility summary with a budgeting range, a phase schedule and the itemized proposal that HELOC, renovation and construction lenders require. The site visit and the estimate are free.