Room Additions in Los Angeles | Cost Per Square Foot, Permits, Timeline

Typical cost: $300 to $600 / sq ftGround floor is cheaper than up
Start to finish: 9 to 18 monthsIncluding drawings and permits
Permit needed: AlwaysDrawings and engineering required
First step: Lot checkWhat zoning actually allows

An addition adds square footage to the house you already own: a bedroom, a primary suite, an office, a bigger living room, or a second floor. In Los Angeles, where lots are small and moving is expensive, it is usually the cheapest way to get more space without leaving the neighborhood.

Before anything gets drawn, we check what your lot allows. Setbacks, height and the city's size limits decide how big you can go, and finding that out first is what keeps you from paying for drawings the city will reject.

Building out versus building upA ground-floor addition needs only a new foundation. A second story means stripping the roof and reinforcing the whole structure underneath, which is why it costs more per square foot.

What it costs in Los Angeles

What	Typical Los Angeles range	Notes
Ground-floor addition	$300 to $500 per sq ft	Simple ones near $250, complex past $600
400 sq ft bedroom and bath	$150,000 to $250,000	The most common size we build
Second-story addition	$400 to $600 per sq ft	Roof comes off, structure below gets reinforced
800 sq ft second floor	$320,000 to $480,000	Including the stairs
Adding a bathroom to the plan	$25,000 to $50,000	On top of the per-foot cost

Planning ranges for Los Angeles County, reviewed 2026-10-29. Not a quote. We price every job after walking it.

What's included

A check of what your lot and zoning actually allow
Architectural drawings and structural engineering
Permit filing, the back-and-forth with the city, and inspections
New foundation to match the existing house
Framing, roofing and an exterior that matches what is already there
Electrical, plumbing and heating and air, extended or new
Insulation, drywall, windows, doors, flooring and paint
Connecting the new space to the existing rooms and roofline

What drives the price

Ground floor or second story. Going up means reinforcing everything below first
Whether the addition includes a bathroom or a kitchen
Soil, slope and drainage, which drive the foundation cost on hillside lots
Matching the existing roof, stucco and windows so it does not look bolted on
What the addition forces you to upgrade: the electrical panel, the sewer line, the heating system

Permits and approvals

Every addition needs a permit with drawings and engineering. In the City of Los Angeles, the size limits and your zoning decide how big you can build, and hillside and historic properties get extra review. Beverly Hills, Santa Monica and Pasadena run their own reviews with their own rules. We check your parcel before anything is drawn so the plans match what will actually get approved.

How long it takes

Drawings and engineering take 6 to 12 weeks. City review runs 2 to 4 months depending on the city. Construction is 4 to 7 months for a ground-floor addition and 6 to 10 months for a second story. You get a written schedule when you sign and an update every week.

Three ways to scope it

Check the lot

Setbacks, height limits and size limits, before design. Tells you what is possible before you spend money.

Draw and permit

Drawings, engineering and the city review. Hillside, historic and fire-zone lots have extra steps.

Build

Fixed scope, a schedule you can hold us to, and a weekly update with photos.

How we run the job

1. Walk the property

We meet you on site, listen, and look at what the building and the city will need. You get a written scope and a budget range.

2. Drawings

When drawings are needed we bring in the architect and engineer, and price the design while it is being drawn.

3. Permit

We file with the city, handle the corrections they send back, and tell you where it stands.

4. Price and contract

An itemized price, a schedule and payment terms. Anything new after signing gets priced in writing first.

5. Build

One supervisor on your job, licensed trades, inspections in order, and a weekly update with photos.

6. Walkthrough

A final fix list, the city's sign-off, and a written warranty on our work.

Questions

How big an addition can I build?

It depends on your zone, lot size, setbacks and the city's floor-area limit. In the City of Los Angeles most single-family homes are capped at a percentage of the lot. We check your specific parcel before any design work, and it costs you nothing.

Is a second story cheaper than building out?

Usually not. Going up keeps your yard but means reinforcing the foundation and the first-floor walls, taking the roof off, and living with the house open for a while. If you have the lot area, building out is typically 25 to 40 percent cheaper per square foot.

Will it match the rest of the house?

Yes. We match the roof pitch, the eaves, the stucco or siding texture, the windows and the trim. You see all of it in the drawings before anyone builds anything.

Can I stay in the house?

For most ground-floor additions, yes. The work happens outside the existing walls until the day we connect the two, and we keep that window short. Second stories are harder to live through and many people move out for part of it.

Will my property taxes go up?

The new square footage gets assessed and added to what you already pay. The rest of the house keeps its existing assessment under Proposition 13. Budget roughly 1.1 to 1.25 percent of the new construction value per year.

Room Additions by city

Same work, different building department. Pasadena, Beverly Hills, Culver City, Long Beach, Santa Monica, Burbank, Sherman Oaks, Encino, Glendale, Studio City, West Hollywood. Or see every city.

Related work

Detached accessory dwelling unit in a back garden

Room Additions & Second Stories