You can almost certainly build an ADU in Santa Monica. California law requires every city to allow at least one ADU and one junior ADU on a single-family lot, protects an 800 square foot unit with four-foot side and rear setbacks at 16 feet of height, bars cities from requiring replacement parking for a garage conversion, and gives the city 60 days to approve or deny a complete application. Santa Monica applies its own design standards and fees on top of that floor.
- Building department
- Santa Monica Building & Safety
- State floor
- 800 sq ft protected4 ft setbacks, 16 ft height
- Decision deadline
- 60 daysOn a complete application
- Typical all-in cost
- $120k to $400kConversion through detached
What state law guarantees you, here and everywhere
- At least one ADU and one junior ADU on a single-family lot
- An 800 square foot unit with 4-foot side and rear setbacks at 16 feet of height, which no local lot-coverage, floor-area or open-space rule can block
- 18 feet of height near major transit or on a lot with an existing multi-storey multifamily building, plus 2 feet to match the main roof pitch
- No replacement parking when you convert a garage
- No owner-occupancy requirement for a full ADU
- A decision within 60 days of a complete application, with 15 business days for the city to confirm completeness
A city cannot opt out of these. Where a local ordinance conflicts with state law, state law governs, and local ADU ordinances that are not properly submitted to the state housing department can be void entirely.
What is specific to Santa Monica
Santa Monica runs its own permits and has its own ADU standards layered on the state floor. The city has also been among the California jurisdictions permitting separate condominium-style sale of ADUs under state law, which is unusual and worth knowing if a future sale is part of your thinking.
Coastal zone rules apply across much of the city. A parcel inside the coastal zone may need a coastal development permit for new construction, which adds review time, though many smaller projects are exempt. We check coastal status by parcel at the start.
Santa Monica also has strong rent control and tenant protection rules. On a property with existing tenants, adding a unit or doing significant construction has notice and habitability implications that need planning before work begins.
- Coastal zone status needs checking parcel by parcel
- Strong rent control affects work on tenanted properties
- The city has permitted separate sale of ADUs under state law
- Its own ADU standards sit on top of the state requirements
Local ordinances, fees and plan availability change faster than any website. We confirm the current Santa Monica requirements against your specific parcel before anything is drawn, and that check costs you nothing.
What it costs
| What | Typical Los Angeles range | Notes |
|---|---|---|
| Junior ADU, inside the house | $60,000 to $120,000 | Up to 500 sq ft |
| Garage conversion | $120,000 to $150,000 | 350 to 400 sq ft |
| Detached ADU, 600 to 800 sq ft | $200,000 to $250,000 | Standard finishes |
| Detached ADU, 1,000 to 1,200 sq ft | $300,000 to $350,000 | Larger units |
Work out your own number. The ADU cost calculator gives you a line-item range for your lot and unit type in under a minute.
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.
Questions
Can Santa Monica refuse my ADU?
Not on a standard unit meeting the state's objective standards. Santa Monica applies its own design standards and fees, and reviews the site-specific parts, but it cannot refuse an ADU that meets state law. Hillside, fire-zone and historic conditions add requirements rather than a veto.
How long does an ADU permit take in Santa Monica?
State law gives the city 60 days to decide a complete application, plus 15 business days to confirm completeness. Real timelines run two to four months once correction rounds are counted. A pre-approved standard plan, where the city offers one and it fits your lot, is far faster.
Do I need to live on the property?
Not for a full ADU. That requirement was removed permanently by state law. For a junior ADU it can still apply where the junior unit shares a bathroom with the main house.
Can I rent it short term?
Generally no. ADU short-term rental is restricted across the region, and junior ADU rentals must run longer than 30 days under state law.
Do you build in Santa Monica?
Yes. We are a licensed California general contractor, CSLB 1083262, working across all of Los Angeles County, and we handle the drawings, the permit and the build.
Related reading
- Can I build an ADU on my property in Los Angeles?
- What are the ADU setback and height rules in Los Angeles?
- What permits do I need for an ADU in Los Angeles?
- What is a junior ADU (JADU)?
- ADU Cost Per Square Foot in Los Angeles
- Garage Conversion Cost in Los Angeles
- Does an ADU Raise Your Property Taxes?
- Pre-Approved ADU Plans in Los Angeles
