An ADU in Los Angeles takes six months to a year from the first site walk to move-in: roughly one to two months of feasibility and design, one to three months of plan check and utility clearances, and three to eight months of construction depending on whether you are converting a garage or building a detached unit from the ground up. Green Design and Build is a licensed general contractor (CSLB #1110975) based in Van Nuys that designs, permits and builds detached ADUs, attached ADUs, garage conversions 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 neighbouring cities). The phase durations on this page are typical Los Angeles planning ranges, not a promise; the two things that most often push a project past a year are utility work and what the site walk did not catch.
We are led by Dekel Sofer. We hold a 4.7-star rating across 146 Yelp reviews and have completed hundreds of projects, and we build across all five counties from our office at 16120 Sherman Way. Our ADU page covers the four unit types and what we check on a site walk; this guide is only about the calendar.
The short answer by ADU type
| ADU type | Typical time from first meeting to move-in | Why |
|---|---|---|
| Garage conversion | Shorter end of six months to a year | No foundation, framing or roof phase; construction runs about three to five months |
| Junior ADU (inside the house, up to 500 sq ft) | Usually the shortest | Existing space, efficiency kitchen, often no new utility service |
| Attached ADU (addition with its own entrance) | Middle of the range | New foundation and framing, but shares walls, roof and utility runs with the house |
| Detached ADU (new backyard unit) | Longer end of six months to a year | Everything is new: foundation, framing, roof, solar, trenching for water, sewer and power |
The six-months-to-a-year figure is the one published on our homepage and it holds up because the middle of the schedule, plan check, is governed by a state deadline that does not care what kind of unit you are building. The ends of the schedule are what change: a detached unit needs more design and engineering up front and more months of construction at the back. A conversion skips both. Our garage conversion cost guide shows the stage-by-stage schedule for a conversion, and our ADU cost guide covers the dollars.
ADU timeline phase by phase
The table is how a typical fully permitted ADU in our service area moves through the calendar. Some phases overlap: utility applications go in during plan check, and a panel upgrade can happen while drawings are still being corrected.
| Phase | Typical duration | What happens |
|---|---|---|
| Feasibility and site walk | 1–3 weeks | Zoning and lot check against state minimums, sewer camera, panel and service check, survey if lot lines are unclear, written feasibility summary and budgeting range |
| Design and engineering | 4–8 weeks | Floor plans, elevations, site plan, selections; or choosing an LADBS pre-approved standard plan for a detached unit in the City of Los Angeles |
| Engineering and Title 24 | Runs inside the design phase | Structural calculations, foundation design, energy compliance forms, soils report where the lot requires one |
| Plan check and permit | Up to 60 days from a complete application, plus corrections | City of Los Angeles through LADBS; other cities through their own building divisions. State law sets the deadline (below) |
| Utility clearances | Overlaps plan check; about 3 weeks for a panel upgrade on the project we describe below | LADWP inside the City of Los Angeles; Southern California Edison or the city utility elsewhere; sewer connection review; water service |
| Construction | 3–5 months (garage conversion) or 5–8 months (detached) | Foundation, framing, utilities, inspections, insulation, drywall, finishes, final inspection |
| Final inspections and occupancy | 1–2 weeks | Final building, electrical, plumbing and mechanical inspections; certificate of occupancy; address and meter set-up if applicable |
The conversion figures in this table are the ones on our garage conversion cost guide. The feasibility and detached-design durations are our working planning ranges, and they are the part of the schedule you control: a homeowner who has chosen a floor plan, a finish level and a budget before design starts shortens design by weeks.
The 60-day rule, and why plan check still takes longer
California Government Code section 66317 requires the permitting agency to tell you in writing within 15 business days whether your ADU application is complete, and then to approve or deny a complete application within 60 days. If the agency does neither within 60 days, “the application shall be deemed approved.” A denial has to come back with a written list of what is deficient and how to fix it. Because the review is ministerial, there is no hearing, no neighbour notice and no discretionary design review for a unit that meets the state standards; our ADU rules pages and ADU rules calculator show what those standards are for your city.
That is the legal floor, and it is why an ADU is faster to permit than a room addition, where plan check runs two to four months. It is not the same as a permit in 60 days, for three reasons:
- The clock starts at “complete.” A submittal missing the Title 24 forms, a site plan with dimensioned setbacks, or the structural calculations does not start the clock. The 15-business-day completeness check is where incomplete packages lose a month.
- Corrections restart the conversation. Plan check comments come back, the drawings are revised and resubmitted, and each cycle takes time on both sides. A clean, complete first submittal is worth more than any expediter.
- Clearances run alongside. Planning clearance, the fire department in a fire zone, hillside grading review, a Historic Preservation Overlay Zone review through the Office of Historic Resources, and the utility applications each have their own queue. The building permit is not issued until they are cleared, and none of them is bound by the 60-day rule.
In the City of Los Angeles, a detached unit built from one of the roughly 60 LADBS pre-approved standard plans skips the design review of the building itself; LADBS reviews only the site-specific items, which “reduces the time required for plan check resulting in faster permit issuance.” LADBS does not promise a number of weeks saved, and neither do we, but a standard plan removes the corrections cycles that come from a custom design.
What delays an ADU in Los Angeles
Every phase in the table can run long, but the same handful of items cause most of the overruns we see. They are all things we look for on the first site walk.
Electrical service and the panel
Many 1950s to 1970s houses in the San Fernando Valley and the older parts of Orange County run on a 100-amp panel that is already carrying the main house. An ADU with a kitchen and a heat pump usually means a 200-amp service upgrade, and that upgrade is scheduled around the utility, not around you. On the 600-square-foot detached ADU in our ADU cost guide, the panel upgrade cost $6,000 to $8,000 and added about three weeks of delay “while waiting on the utility company’s timeline.” Inside the City of Los Angeles the service change goes through LADWP; in Orange County, Ventura County, western Riverside County and western San Bernardino County it goes through Southern California Edison or the city’s own utility. The work is performed by licensed electricians and scheduled and supervised by us as your general contractor; our electrical page explains the panel work. Filing the utility application during plan check, not after the permit, is how we keep it off the critical path.
The sewer lateral
A detached ADU needs a drain line to the street or to the house lateral, and on the same project above the excavation for the new foundation uncovered an old clay sewer line with cracks and root intrusion. Rerouting it cost approximately $14,000 and added work nobody had scheduled. A camera inspection before design costs a fraction of that and turns a surprise into a line item. The plumbing is performed by licensed plumbers and scheduled and supervised by us; see our plumbing page.
Soils, slope and hillside review
A flat Valley lot with a two-car driveway needs no soils report. A hillside lot in Sherman Oaks, Encino or Studio City, a sloping lot in Glendale or Thousand Oaks, or a property with a retaining wall between the house and the ADU site usually needs a geotechnical report before the foundation can be engineered, and in the City of Los Angeles a hillside lot goes through additional grading and access review. That adds weeks at the front of the schedule and can add a month or more of foundation work at the back.
Fire hazard zones
Since CAL FIRE’s March 2025 maps, much of the hillside Valley, the Santa Monica Mountains and the Orange County canyons sit in a Very High Fire Hazard Severity Zone. An ADU there is built to Chapter 7A of the building code: ember-resistant vents, Class A roof assembly, tempered or multi-pane glazing, and protected eaves. None of that is slow to build, but the fire department review is a separate clearance, and the materials have longer lead times than standard products.
HOA and CC&R review
Civil Code section 4751 makes any covenant that “effectively prohibits or unreasonably restricts” an ADU on a single-family lot void and unenforceable, but it still allows reasonable restrictions, and it does not remove the architectural review step. In master-planned communities in Irvine, Anaheim Hills, Rancho Cucamonga and Corona, plan on a review cycle before you submit to the city, and get it started during design rather than after.
Selections and change orders
The single largest cost movement on the project above was not a hidden condition: the owners added roughly $30,000 of finish upgrades after framing. Changes after rough-in are also the most common self-inflicted delay, because tile, cabinets and fixtures ordered late arrive late. Choose finishes before drywall, and expect custom cabinetry to take about three weeks to manufacture.
A real detached ADU that went from $180,000 to $265,000
The project we keep referring to is retold in full in our ADU cost guide. The homeowners had already removed an old, deteriorated garage and planned a roughly 600-square-foot one-bedroom, one-bath detached ADU on a budget of approximately $180,000. Three things moved it to about $265,000: the clay sewer line found under the new foundation (about $14,000 to reroute), the 200-amp panel upgrade ($6,000 to $8,000 and around three weeks waiting on the utility), and approximately $30,000 in finish upgrades chosen after framing. Two of the three were schedule problems as much as budget problems, and both are now standard checks on our site walk. Those figures, like every cost range we publish, are typical Los Angeles budgeting estimates, not a price list or a quote; a project can come in lower or higher. For a garage conversion, the equivalent story is the two-car garage in why ADU quotes vary so much that went from an $85,000 to $95,000 estimate to about $130,000 after the slab, the panel and the sewer were opened up.
A finished example of the conversion route is our garage-to-ADU conversion in Los Angeles, completed in 2025: a plain stucco garage of about 500 square feet with one wide door opening became a self-contained rental with a rebuilt roof structure, new framing and sheathing, new windows and French doors, a full kitchen and a full bathroom.
How to keep an ADU on schedule
- Do the feasibility work first. Sewer camera, panel check, lot-line and setback check, fire-zone and hillside status. Every item found here is a change order avoided later.
- Decide what the unit is for before design. A rental studio, a parent’s suite and a home office want different floor plans, and changing your mind after engineering costs weeks.
- Submit a complete package. Title 24, structural calculations, dimensioned site plan, and the soils report if the lot needs one. The 60-day clock only starts on a complete application.
- File utility applications during plan check. Service upgrades are on the utility’s calendar; the earlier the application, the less it matters.
- Finalize selections before rough-in. Cabinets, tile, fixtures, windows and doors with long lead times should be ordered while framing is still going up.
- Use a standard plan in the City of Los Angeles if one fits. For a detached unit, the LADBS catalogue avoids the design corrections that slow custom plan check.
- Hold a contingency. Our ADU cost guide recommends 15 to 20 percent above the accepted bid; a contingency also buys schedule, because a funded change order is approved in a day and an unfunded one waits.
Financing has a calendar too. A HELOC or a construction loan with a draw schedule needs to be in place before the deposit, which under California law is capped at $1,000 or 10 percent of the contract price, whichever is less; our financing page explains the programs we offer.
Where we do this work
An ADU schedule depends on who reviews it. Inside the City of Los Angeles and most of the San Fernando Valley, plans go to LADBS, the utility is LADWP, and detached units can use the standard plan catalogue. In Orange County every city runs its own building division and master-planned communities add HOA review before submittal. Ventura County cities such as Thousand Oaks and Simi Valley review their own permits, with Ventura County Building and Safety covering unincorporated areas, and hillside lots there often need a soils report. In western Riverside County and western San Bernardino County, Corona, Riverside, Ontario and Rancho Cucamonga have their own departments, newer housing stock with 200-amp panels already in place, and expansive soils that can require a geotechnical report. See all of our service areas.
ADU timeline FAQs
How long does it take to build an ADU in Los Angeles?
A fully permitted ADU in Los Angeles typically takes six months to a year from the first site walk to move-in. Feasibility and design take one to three months, plan check and utility clearances one to three months, and construction three to five months for a garage conversion or five to eight months for a detached unit. Hillside, fire-zone and historic reviews, and utility service upgrades, are the usual reasons a project runs toward the long end.
How long does ADU plan check take in Los Angeles?
Under California Government Code section 66317, the city must tell you within 15 business days whether your ADU application is complete and then approve or deny a complete application within 60 days, or it is deemed approved. In practice plan check runs one to three months once corrections cycles and planning, fire and utility clearances are included. A complete first submittal is the single biggest factor in staying near 60 days.
Is a garage conversion faster than a detached ADU?
Yes. A garage conversion ADU in Los Angeles sits at the shorter end of the six-month to one-year range because there is no foundation, framing or roof phase, and construction typically takes three to five months. A detached ADU needs more design and engineering up front and more months of construction, so it sits at the longer end. Both go through the same 60-day plan check rule.
What is the biggest cause of ADU delays?
Utility work is the most common cause of ADU delays in Los Angeles. On a detached ADU project we have written about, a 100-amp to 200-amp panel upgrade added about three weeks waiting on the utility, and an old clay sewer line found under the new foundation added unplanned excavation. Filing the utility application during plan check and running a sewer camera before design are the two best ways to avoid both.
Does an LADBS standard plan make an ADU faster?
Using one of the LADBS pre-approved standard plans for a detached ADU in the City of Los Angeles lets plan check focus on site-specific items such as zoning and foundation, which LADBS says reduces plan check time and results in faster permit issuance. LADBS does not state a specific number of weeks saved. Standard plans apply to new detached units, not to garage conversions, which go through regular plan check with their own drawings.
How much time should I add for a hillside or fire-zone lot?
A hillside lot in Los Angeles usually needs a geotechnical report before the foundation can be engineered, which adds weeks at the front of an ADU schedule, and hillside grading review is a separate clearance from the building permit. A lot in a Very High Fire Hazard Severity Zone adds a fire department review and Chapter 7A materials with longer lead times. Neither changes the 60-day plan check rule, but both add clearances that run outside it.
Find out how long your ADU will take before you commit
Give us your address and what you want the unit to do, and we will walk the lot, camera the sewer, check the panel and the fire-zone and hillside status, and give you a written feasibility summary with a phase-by-phase schedule for your property. The site visit and the estimate are free.