Answers › How much does an ADU cost in Santa Monica?
How much does an ADU cost in Santa Monica?
In 2026, a garage conversion ADU in Santa Monica typically costs roughly $150,000 to $280,000, and a new detached ADU runs from about $150,000 for a compact unit near 400 square feet to $600,000 or more for an 800 to 1,000 square foot unit with significant site work. Coastal Zone review, utility upgrades and finish level are the biggest swing factors, so these are planning ranges, not quotes.
| Garage conversion ADU | Roughly $150,000 – $280,000 |
|---|---|
| Detached ADU | Roughly $150,000 (compact) – $600,000+ (large, with site work) |
| Permit decision | Within 60 days of a complete application (state law) |
| Extra for Santa Monica | City plan check, possible Coastal Zone review, tight-lot logistics |
Why Santa Monica ADUs cost more than the Los Angeles average
Santa Monica adds three things to an ADU budget that most of Los Angeles does not: a separate city permit process with its own fees and plan check, Coastal Zone review for properties in the western part of the city, and tight lots where staging, parking and material deliveries cost real money. Labor and finish expectations in the 90401 to 90405 zip codes also sit above the county average.
What drives the number
The structure you start with matters most. A garage conversion keeps the walls, roof and slab, so the budget goes to foundation repairs where the slab is cracked or unlevel, fire-rated separation from the main house where required, insulation, a new electrical subpanel, plumbing tie-ins and a compact kitchen and bathroom. A detached new build adds a foundation, framing, roofing and full exterior, and the per-square-foot cost rises as the unit gets smaller because the kitchen, bathroom and utility connections are fixed costs regardless of size.
Utilities are the hidden line item. Many older Santa Monica homes run on 100-amp service that cannot carry a second dwelling, and a sewer lateral that is already at capacity may need replacement. Budget a utility survey early.
A realistic way to budget
Get the site facts first: lot survey, Coastal Zone status, existing electrical service, sewer location and soil conditions if the lot is sloped. Then price the unit as a complete scope, including design, engineering, permit fees, utilities and landscaping repair, not just the box. Oria Builders (CSLB #1029255) builds Santa Monica ADUs from its office on Main Street and prices every project from a written scope; confirm current fees and requirements with the City of Santa Monica before committing to a number.
Related Questions
Does a Santa Monica ADU need a Coastal Development Permit?
If the property is in the Coastal Zone, usually the blocks closest to the beach, a new unit generally needs a Coastal Development Permit or a written exemption in addition to the building permit. Check the parcel against the city's Coastal Zone map first.
Is a garage conversion cheaper than a new ADU?
Usually, because the structure and slab already exist. The savings shrink when the slab has to be replaced or the garage needs new fire separation and a full utility upgrade.
Can I rent out a Santa Monica ADU?
ADUs may be rented for terms of 30 days or more under California law. Short-term rentals are regulated separately by the city, so confirm the current rules before planning on nightly rental income.
Sources
Related
- General contractor in Santa Monica
- ADU Construction
- Project: Full Remodeling and garage conversion to an ADU in Los Angeles – Precision Punch List Completion
- Case study: Modern ADU Creation in Santa Monica’s Ocean Park Neighborhood
- How long does a remodel permit take in Santa Monica?
- What is the Coastal Zone and how does it affect remodeling in Santa Monica?
- How much does a 400-square-foot ADU cost?
Answered by Gilad Segev — Founder & Licensed General Contractor, Oria Builders (CSLB #1029255). Last updated October 2, 2026.