A second-story addition in Los Angeles typically costs $400 to $650 per square foot all-in: $200,000 to $350,000 for a partial second story of 400 to 600 square feet, and $350,000 to $650,000 or more for a full second story of 800 to 1,200 square feet, including design, engineering, permits, construction and standard finishes. Green Design and Build is a licensed, bonded and insured general contractor (CSLB #1110975) based in Van Nuys, serving homeowners across Los Angeles County, Orange County, Ventura County, western Riverside County and western San Bernardino County (Ontario, Rancho Cucamonga and neighbouring cities). 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, and the only real number is a written proposal after a site visit.
Who we are
Green Design and Build is led by Dekel Sofer. We hold a 4.7-star rating across 146 Yelp reviews and have completed hundreds of projects across the five counties above. Our room additions page covers how we build additions; this guide is about what a second story costs, why, and when it is the wrong answer.
Second-story addition cost by size
Every range below assumes a wood-frame single-story house on a flat lot and includes drawings, engineering, the Title 24 report, plan check and permit fees, the structural work through the first floor, the new roof, systems and standard finishes.
| Addition | Typical size | Typical Los Angeles budgeting estimate |
|---|---|---|
| Partial second story (one or two rooms over part of the house) | 400–600 sq ft | $200,000–$350,000 |
| Full second story | 800–1,200 sq ft | $350,000–$650,000+ |
How we estimated these numbers
The ranges on this page are budgeting estimates for Southern California, not a price list. They are drawn from Green Design and Build’s own written proposals and completed projects across Los Angeles, Orange, Ventura and western Riverside and San Bernardino counties, checked against current supplier and subcontractor pricing. A real project can come in lower or higher depending on the house, the scope and the finishes. Reviewed by Dekel Sofer, licensed general contractor (CSLB #1110975), September 2026. Publishers and journalists are welcome to cite these figures with a link to this page.
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 arithmetic: a 500 square foot partial second story at $400 to $650 per square foot is $200,000 to $325,000; a 1,000 square foot full second story is $400,000 to $650,000. Two bathrooms and a laundry upstairs put a project high in its range; two dry bedrooms over the garage wing put it low. Our room addition cost guide has the full addition table, and our guide to what a Los Angeles general contractor costs shows where additions sit against other projects.
Why a second story costs $400 to $650 per square foot
A ground-floor addition in Los Angeles runs $300 to $500 per square foot. The second-story premium, roughly $100 to $150 more per square foot, pays for what has to happen to the house underneath the new rooms.
The foundation has to be verified, and often improved
The existing footings were sized for one floor. Before the engineer can draw the second story, we expose sections of the foundation, measure the footing width and depth, and check the concrete and the anchor bolts. On a 1950s to 1970s Valley ranch house the footing is often narrower than two stories need, and the fix ranges from new footings under the new bearing points to underpinning the existing stem wall. As typical Los Angeles budgeting estimates, foundation underpinning runs $10,000 to $40,000, and a bolt-and-brace retrofit, which the engineer usually folds into the design on a pre-1980 raised-foundation house, runs $4,000 to $12,000.
New shear walls, posts and beams through the first floor
A second story changes the load path of the whole house. The engineer adds plywood shear walls with hold-downs at the first floor to resist the earthquake and wind loads of the taller building, and new posts and beams to carry the second-floor joists down to the footings. That work runs through finished rooms: drywall comes off, kitchen cabinets sometimes come out, and closets get thicker. The stair takes floor area from the first floor, usually a bedroom or a corner of the living room, and that lost room is decided before any drawing is made.
The roof comes off and a temporary roof goes on
The existing roof and ceiling framing are removed, the new floor is framed over the first-floor walls, and the house is open to the sky until the second-floor walls and new roof are up. We schedule this phase for the dry months where we can and cover the house with a temporary membrane; it is the most expensive stretch of the project.
Systems that were sized for one floor
A second story almost always needs its own HVAC zone, because the existing furnace and ducts cannot reach it, and new bathrooms need drains routed down through the first floor. Many Valley houses still run on a 100-amp panel, and a new floor with a heat pump, bathrooms and bedrooms usually pushes it to a 200-amp upgrade, which our electrical page puts at $4,000 to $8,000 for an overhead service, or $8,000 to $15,000 or more if the utility has to change the service. Where demolition exposes original cloth-wrapped or aluminum wiring, a whole-house rewire at $15,000 to $35,000 often makes sense while the walls are open. Electrical, plumbing and HVAC work is performed by licensed electricians, plumbers and HVAC contractors and scheduled and supervised by us as your general contractor.
Living somewhere else
Temporary housing is not in the construction estimate, but it is in the budget. Most families move out for the five to seven months of construction, because there is no ceiling, and at times no water or power, for weeks at a time. Put a number on the rent before you compare options.
Build up or build out?
The choice usually decides itself once you look at the lot.
| Build out (ground-floor addition) | Build up (second story) | |
|---|---|---|
| Typical Los Angeles budgeting estimate | $300–$500 per sq ft | $400–$650 per sq ft |
| Best when | The lot has room within setbacks and floor-area limits | The lot is small or already built out; you want to keep the yard, pool or a future ADU site |
| Structure | New footings and slab or raised floor; tie-in beam at the existing wall | Foundation verification, new footings, shear walls, posts and beams through the first floor |
| Living at home during construction | Usually yes | Usually not |
| Construction time | 4–7 months | 5–7 months |
| Total, first meeting to final inspection | 9–14 months | 9–14 months |
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.
Build out when the lot allows it and the space you want (a primary suite, a bigger kitchen, a family room) belongs on the main floor. Build up when a ground-floor addition would consume the backyard on a 5,000 to 6,000 square foot lot, or when you want the bedrooms upstairs and one open living floor below.
What the City of Los Angeles lets you build
Zoning decides whether the second story you want can exist, so we check four things before design starts.
Floor area. Under the Baseline Mansionization Ordinance, the residential floor area of a house on most R1 lots is capped at 45 percent of the lot area, existing square footage included. A 6,000 square foot R1 lot allows about 2,700 square feet of house; if the existing house is 1,500 square feet, roughly 1,200 square feet is available for a second story before exemptions and overlays. RS, RE, RA and the R1 variation zones use different ratios.
Height and the encroachment plane. On an R1 lot outside the hillside and coastal areas, the Municipal Code limits the house to 33 feet where the roof of the top floor slopes 25 percent or more, and 28 feet where it is flatter. Second-story walls must also stay inside an encroachment plane that starts 20 feet above grade at the side setbacks, which is what produces the stepped-back second stories you see on 50-foot Valley lots.
Setbacks. The new floor sits inside the same envelope as the first: a front yard of 20 feet or the prevailing setback, 5-foot side yards and a 15-foot rear yard on a standard R1 lot. A second story over a garage built to the property line under an older permit usually is not possible.
Overlays. In a Historic Preservation Overlay Zone, every exterior addition is reviewed under the HPOZ preservation plan before Building and Safety will take the plans, and a second story on a contributing single-story bungalow is often the one addition the board will not approve because it changes the streetscape. Hillside lots add the Baseline Hillside Ordinance’s slope-based floor area and grading limits and a geotechnical report; coastal lots add a Coastal Development Permit. Outside the City of Los Angeles, every city applies its own floor-area, height and setback rules, and master-planned communities add HOA architectural review before the city will issue anything.
When a detached ADU is the better answer
Sometimes the honest recommendation is not to add a second story at all. State law requires cities to approve a detached ADU of up to 800 square feet with 4-foot side and rear setbacks even where the lot’s floor-area cap or lot coverage would block an addition of the same size. An ADU is approved ministerially, you stay home during construction, its foundation and roof are new rather than retrofitted, and it can be rented or house a parent, which an addition cannot legally do. Our published ADU figures put a detached 500 square foot unit at $180,000 to $260,000, against $200,000 to $350,000 for a partial second story of similar size. Choose the second story when the space has to connect to the existing rooms or you want bedrooms over the living floor. Our guide to ADU vs room addition and our ADU page walk through the decision; if the house is a teardown candidate, see new home construction.
How long a second-story addition takes
| Phase | Typical time |
|---|---|
| Design, structural engineering and Title 24 | 8–12 weeks |
| Plan check and permits (LADBS or the city) | 2–4 months |
| Construction | 5–7 months |
| Total, first design meeting to final inspection | 9–14 months |
A second story cannot use an LADBS Express Permit; it goes through full Building Plan Check with structural calculations, then staged inspections from the exposed footings through framing, shear nailing, rough trades and final. HPOZ, hillside and HOA reviews sit in front of plan check, and each correction cycle adds weeks. Demolition does not start until the permit is in hand.
What opening up a 1950s house finds
We have not yet published a second-story project story, but the discoveries are the ones we describe in our ADU cost guide, because the same kind of house is being opened up. On that project, a roughly 600 square foot detached unit the owner expected to cost about $180,000, digging the foundation exposed the main house’s original clay sewer line, cracked and full of roots; rerouting it cost about $14,000. The 100-amp panel was full, and an electric range and heat pump forced a 200-amp upgrade at about $6,000 to $8,000 with about three weeks of utility delay. Selections made during framing added about $30,000, and the unit finished at about $265,000. On a second story the equivalent surprises are an undersized footing, an unbolted sill, a rotted top plate and a full panel, which is why we hold 15 to 20 percent of the accepted bid as a contingency on any pre-1980 house.
When you compare quotes, ask each bidder to put the foundation assumptions, the structural scope, the HVAC zone and panel, the roof and stucco scope and the finish allowances in writing. A bid without the foundation and structural scope written down is not the low bid; it is the one that has not been priced yet.
Where we do this work
Most of our second-story additions are in the San Fernando Valley and the rest of Los Angeles County, where single-story ranch houses on small lots, LADBS plan check and the 45 percent floor-area cap shape the project. In Orange County city building divisions and HOA review run side by side. Ventura County adds fire-zone construction on hillside lots in Thousand Oaks and Simi Valley. Western Riverside County and western San Bernardino County bring newer slab houses on expansive soils in Corona, Eastvale, Ontario and Rancho Cucamonga. Every city and county we serve is on our service areas page.
Second-story addition cost FAQs
How much does a second-story addition cost in Los Angeles?
A second-story addition in Los Angeles typically costs $400 to $650 per square foot all-in, or $200,000 to $350,000 for a 400 to 600 square foot partial second story and $350,000 to $650,000 or more for a full 800 to 1,200 square foot second floor, including design, engineering, permits, construction and standard finishes. These are typical budgeting estimates, not a price list; a real project can come in lower or higher.
Why does a second story cost more than a ground-floor addition?
A second story costs roughly $100 to $150 more per square foot than a ground-floor addition in Los Angeles because the existing foundation must be verified and often underpinned, new shear walls, posts and beams run through the first floor, the roof comes off and is rebuilt, the new floor needs its own HVAC zone and often a 200-amp panel, and most families pay rent elsewhere for the roof-off phase. The rooms upstairs are the cheap part.
Is it cheaper to build up or build out?
Building out is cheaper per square foot in Los Angeles, at $300 to $500 against $400 to $650 for building up, and it usually lets you stay in the house. Building up is the better choice on a small lot where a ground-floor addition would take the yard, when the house is near its 45 percent floor-area cap and the yard is worth keeping, or when you want the bedrooms upstairs.
Can my foundation support a second story?
Most single-story Los Angeles houses can carry a second story, but a structural engineer has to verify the existing footings first, and on 1950s to 1970s houses the footing is often narrower than two stories require. The usual fixes are new footings under the new bearing points or underpinning, which runs $10,000 to $40,000 as a typical Los Angeles budgeting estimate, plus anchor bolts and cripple-wall bracing on a pre-1980 raised foundation.
How tall can a second story be in Los Angeles?
On a standard R1 lot in the City of Los Angeles outside the hillside and coastal areas, the house may be 33 feet tall where the roof of the top floor slopes 25 percent or more and 28 feet where it is flatter, and second-story walls must stay inside an encroachment plane that begins 20 feet above grade at the side setbacks. Hillside lots use the Baseline Hillside Ordinance, and other cities set their own limits.
Do I have to move out during a second-story addition?
Yes for most of the project. The roof comes off, the first floor is opened for shear walls, posts and beams, and the house has no ceiling, and at times no water or power, for weeks, so most families move out for the five to seven months of construction. Temporary housing is not in the construction estimate; budget for it before comparing a second story with a ground-floor addition or an ADU.
Find out whether your house can take a second story before you budget for one
Send us the address and what you need the space for. On a free site visit we check the floor-area allowance, the height limit and overlays for your lot, look at the foundation and the panel, and tell you whether to build up, build out or build an ADU, then give you a written, itemized estimate for the option that makes sense.