- Typical cost
- $300 to $600 / sq ftSanta Monica, 2026
- Building department
- City of Santa Monica
- Permit needed
- Always
- Licensed
- CSLB 1083262Class B general building
Additions in Santa Monica are constrained by lot size more than by rules on most parcels, and by coastal development permit requirements on the parcels near the water. Second storeys are common here precisely because the lots do not leave room to build out.
What it costs in Santa Monica
| 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 |
Los Angeles County figures, reviewed 2026-10-29 by America General Contractors, California contractor licence CSLB 1083262. Planning ranges, not a quote, and not legal advice. We confirm the current rules for your parcel before anything is drawn.
How we approach it here
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 rules in Santa Monica
Santa Monica runs its own permits and plan check, has a seismic retrofit ordinance covering soft-story, unreinforced masonry and some concrete buildings, and applies Coastal Commission rules west of certain streets. The city also has strong rent control and tenant relocation rules that affect multifamily renovations.
Building department
City of Santa Monica Building & Safety
ZIP codes we cover
90401, 90402, 90403, 90404, 90405
Neighborhoods
North of Montana, Sunset Park, Ocean Park, Mid-City, Wilshire-Montana
What a room additions job includes
- 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 moves 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 inspections
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 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.
Santa Monica questions about room additions
Do I need a permit for room additions in Santa Monica?
City of Santa Monica Building & Safety 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 much does room additions cost in Santa Monica?
$300 to $600 / sq ft is the usual range across Los Angeles County, and Santa Monica sits inside it. The table on this page breaks it down by scope. What moves the number locally is the condition of the existing house and whether the layout changes, not the ZIP code. We price from a walkthrough, not a square-foot rule.
How long does room additions take in Santa Monica?
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.
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.
Other work we do in Santa Monica
kitchen and bathroom remodeling, ADU and garage conversion work, whole-house renovation, seismic retrofit and foundation work. Or see everything on the Santa Monica page.
Room Additions in nearby cities
Pasadena, Beverly Hills, Culver City, Long Beach, Burbank, Sherman Oaks.