Building an ADU in Santa Monica

What you can build in Santa Monica

You can add an ADU or junior ADU (JADU) on any legal lot zoned for single-unit or multiple-unit homes, with a home already there or proposed with the ADU. The rules are in Santa Monica Municipal Code section 9.31.025, amended in October 2024 (Ordinance No. 2792CCS) and May 2025 (Ordinance No. 2814CCS). An ADU that meets them is approved by-right, without a hearing.

The code gives you two paths:

• Santa Monica permitted ADUs are the city's own, more generous standards: bigger units (up to 1,200 sq ft) and taller detached ADUs (two stories, 24 feet), but the zone's front setback applies.
• State mandated ADUs follow state law: a converted ADU and a JADU, and a new detached ADU of up to 800 sq ft with 4-foot side and rear setbacks and state height limits. The city can't add other objective development or design standards to these.

On a single-family lot you can have one converted ADU, one JADU and one new detached ADU. In the R1 (single-unit) zone you can add one more ADU, detached or as a new addition to the house, if it is used as a rental under a deed restriction or sold as a condominium.

On multifamily lots you can convert non-living space inside the building (storage rooms, boiler rooms, attics, basements, garages and similar) into at least one ADU or up to 25% of the existing units, whichever is greater. You can also build up to eight detached ADUs on a lot with an existing apartment building (no more than the number of existing units), or two with a proposed one. No ADU or JADU is allowed on a lot with a multiple-unit ownership project approved under Government Code 66499.41. For the state rules, see our California page. [1]

How the code answers the state's review

In February 2024, California's housing department (HCD) told Santa Monica that its ADU Ordinance No. 2742 (2023) did not comply with state ADU law. Among other points, HCD said the city must allow a converted ADU, a new detached ADU and a JADU together on a single-family lot; allow JADUs only on single-family-zoned lots; allow multifamily conversions only inside the apartment building; not require detached ADUs to sit in the rear half of the lot; and use state approval-or-denial wording for the 60-day deadline. HCD added that the city's extra R1 ADU could carry a rental deed restriction only once the state-required combinations were allowed, and that a deed restriction "in a form approved by the City Attorney" is not an objective standard.

The current code, amended in 2024 and 2025, now allows the three-unit combination, limits JADUs to single-family-zoned lots, keeps multifamily conversions inside the building, and drops the rear-half rule. The extra R1 ADU still needs a deed restriction "in a form approved by the City Attorney."

One rule that now conflicts with state law: the code still requires the owner to live in the house or the JADU for every JADU. Since January 1, 2026, state law requires owner occupancy only when the JADU shares a bathroom with the house. State law generally overrides a stricter local rule, so confirm with City Planning. [1][2][3]

Size, height and setbacks

Size (Santa Monica permitted ADUs). Every ADU must be at least 150 sq ft of floor area.

• New detached ADU: up to 850 sq ft for a studio or one bedroom, 1,200 sq ft with more than one bedroom.
• ADU converted from space in the house: the same limits, or 50% of the existing house if that is less.
• ADU converted from a detached accessory building: limited to the existing floor area, plus any allowed expansion.
• New ADU added onto a house in R1: 850 / 1,200 sq ft, or 50% of the house if less.
• State-mandated detached ADU: up to 800 sq ft.

Height. A Santa Monica permitted detached ADU can be two stories and 24 feet (24 feet on multifamily lots too). An ADU inside or added onto the house follows the zone's height limit for the house. A state-mandated detached ADU follows the state height limits; HCD says those are at least 16 feet, 18 feet within a half-mile walk of major transit, plus 2 feet to match the house's roof pitch.

Setbacks. New ADUs need 4 feet from side and rear lot lines, and the city's own standards keep the zone's front setback. No setback applies to existing living space or an existing accessory building converted to an ADU, or one rebuilt in the same place and size. A conversion in the front setback can grow up to 150 sq ft into it, only for entry and exit. Under the code, "detached" means at least 4 feet from the main house, wall to wall; the city's pre-approved ADU page says 6 feet, so confirm with City Planning.

Upper-story outdoor space rules and the zone's stepback rules (for ADUs in or added onto the house) also apply. [1][3][4]

Parking

Santa Monica requires no parking for an ADU or JADU. If you tear down or convert a garage, carport or parking space to build one, you don't have to replace it. Any parking you choose to add must meet the city's parking standards. If your ADU moves or displaces existing parking, the city may require you to close your curb cut; ask the Mobility Division. [1][4]

Fees

ADUs and JADUs built under section 9.31.025 are exempt from Santa Monica's four development impact fee programs: Affordable Housing Production, Child Care Linkage, Transportation Impact Fee, and Parks and Recreation. The city's pre-approved plan page notes that ADUs over 750 sq ft may be subject to Public Works impact fees, so ask Public Works about yours.

You pay initial plan check fees when you submit, and final fees before the permit is issued. Every ADU needs its own address, through an Address Application. Under state law, ADUs and JADUs under 500 sq ft of interior livable space are not subject to school impact fees.

For typical construction costs see our ADU cost guide, and for financing, our ADU financing guide. [1][3][4]

How long it takes

ADU and JADU applications are approved ministerially, without a hearing. On a lot with an existing home, the city must approve or deny a complete application within 60 days, or it is deemed approved (the clock pauses if you ask for a delay). If you apply together with a new house, the ADU is decided along with the house. A denial must come with a written list of what is wrong and how to fix it. The city can't deny an ADU because of nonconforming conditions or unpermitted structures that don't threaten health and safety and aren't affected by the ADU. Under state law, the city must also tell you within 15 business days whether your application is complete.

Santa Monica's building permit process is paperless: you upload everything to the city's Electronic Plan Review System before visiting the counter. Plans are first prescreened for completeness, then routed to each department; you resubmit if there are corrections. Plans are currently reviewed under the 2025 California building codes, in effect since January 1, 2026. See our ADU permit process guide.

Coastal zone. Part of Santa Monica is in the California coastal zone. In a 2022 report approving one Santa Monica ADU through a permit waiver, the California Coastal Commission noted that the city's zoning code is uncertified for the coastal zone and that the Commission has regularly found an ADU is not equivalent to a full unit under the city's certified Land Use Plan. The city lists its Local Coastal Program as a current planning project. If your lot is in the coastal zone, ask City Planning what coastal approval you need before you apply. State law requires a coastal development permit for an ADU to be approved or denied within 60 days of a complete application. [1][3][4][5][6][7]

Garage conversions, junior ADUs and unpermitted units

Garage conversions. You can convert a garage or other existing accessory building into an ADU with no setback beyond what exists, and you don't replace the parking. Under the state-mandated path you may add up to 150 sq ft beyond the building, only for entry and exit; side and rear setbacks just need to be enough for fire safety. The city's ADU conversion information bulletin lists building code requirements for one-story conversions (footings, egress windows, fire-rated walls near lot lines) and the plans you need. It says sprinklers are needed only if the main house must be fully sprinklered. See our garage conversion guide.

Junior ADUs. A JADU is 150 to 500 sq ft inside the existing or proposed house, including an attached garage. It needs a separate entrance, an efficiency kitchen (cooking appliances, a prep counter and storage cabinets), and, if it has no bathroom of its own, an interior door to the house. You must record a deed restriction that bars selling the JADU separately. See our junior ADU guide.

Unpermitted units. The 2023 bulletin says unpermitted accessory buildings built before January 1, 2018 can be converted in place, and lists evidence that proves the build date (code enforcement orders, rent control registration, receipts, utility bills or a lease). It cites the old state code sections, so confirm current rules with Building and Safety. [1][8]

Renting it out and selling

ADUs and JADUs can't be rented for 30 days or less, except as permitted under the city's Home-Sharing and Vacation Rentals law (SMMC Chapter 6.20). State-mandated ADUs must be rented for more than 30 days. Since 2026, state law also bars short-term rental of any JADU. Santa Monica lease rules that apply to all homes apply to ADUs too.

Selling. Santa Monica allows ADUs to be sold as condominiums under SMMC 9.31.026. You need a subdivision map and condominium plan under the Subdivision Map Act and the Davis-Stirling Act, a safety inspection (a certificate of occupancy or a HUD-certified inspector's report), written consent from every lienholder, and approval from any existing homeowners association. Projects of four or fewer parcels don't go to the Planning Commission. You must notify water, sewer, gas and electric providers. An ADU can also be sold to a qualified buyer under state law (Government Code 66340). JADUs can't be sold separately.

Lot splits. The code points to its duplex and lot split rules for single-unit zones; ADUs can't push a lot over the unit count those allow. See our SB 9 lot split guide. [1][3]

Pre-approved ADU plans

Santa Monica runs a Preapproved ADU Program under which architects and designers can submit standard plans for detached ADUs for preapproval. As of October 2026 the city lists no preapproved plans ("NONE AT THIS TIME"). When plans are listed, you pick one, work with its vendor to add site details, complete a Hold Harmless Agreement, and submit with "ADU per Standard Plan No." on the application for an expedited review. No changes to a preapproved plan are allowed, and plans are valid only within the building code cycle in which they were approved. To compare with factory-built options see our prefab ADU guide. [4]

Permit steps in Santa Monica

1. Check the rules for your lot

   Read SMMC 9.31.025 and decide between the city's standards and the state-mandated path. Book a zoning consultation at the Permit Services Center or call City Planning at (866) 311-7266. If you are in the coastal zone, ask what coastal approval you need. [1][7][9]

2. Prepare plans

   Hire a designer, or use a preapproved standard plan if any are listed. The city's plan review supporting documents include structural calculations, a Title 24 energy report and, for new construction, a soils report. [4][5]

3. Apply for an address

   Every ADU needs its own address; complete the city's Address Application with a site plan and address plan. [4]

4. Submit online and pay initial fees

   Upload your application and plans to the Electronic Plan Review System and pay initial plan check fees. Plans are prescreened for completeness, then routed for review. [4][5]

5. Respond to corrections

   Resubmit revised plans if corrections are issued. The city must approve or deny a complete application within 60 days, or it is deemed approved. [1][4]

6. Pay final fees, get your permit and schedule inspections

   After approval, pay final fees and get your permit; construction needs inspections at stages through final approval. If you used a JADU, record the required deed restriction. [1][4][5]

Pre-approved and sample plans

• Preapproved ADU Program

  Vendors can get standard detached ADU plans preapproved for expedited review; the city listed none as of October 2026. [4]

Who to call

• Santa Monica Permit Services Center

  Permit issuance, building code and zoning consultations; open 8 a.m.-3 p.m. Monday-Thursday, appointments at checkin.smgov.net

  1685 Main Street (south entrance, from Olympic Dr.), Santa Monica, CA 90401

  [9]

• Santa Monica Building and Safety Division

  Plan review, inspections and permit records

  (866) 311-7266

  [5][7]

• Santa Monica City Planning Division

  Zoning rules for ADUs, the Local Coastal Program

  (866) 311-7266

  [7][10]

• Santa Monica Community Development Department

  Main department line

  (310) 458-2275

  [7]

Questions people ask