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ADU design-build · Costa MesaADUs in Costa Mesa
Mid-century homes close to the coast and steady rental demand: in Costa Mesa, an ADU is often the simplest way to add a home on land that is already yours.
What applies to your lot
Building an ADU in Costa Mesa
Who approves your ADU
City of Costa Mesa: ADUs follow Section 13-35 of the Zoning Code, updated in 2025 to match state law, and reviewed by Economic and Development Services. State law applies everywhere: a decision within 60 days of a complete application, no public hearing, and at least 800 sq ft with 4 ft side and rear setbacks.
Room to go up
Where the zone allows it, Costa Mesa permits two-story ADUs, with added setbacks for the upper floor. On a tight lot, that can mean a real one- or two-bedroom home.
Talk to a planner first
The city recommends a meeting with a planner before submitting. We prepare that conversation with your lot data, so it answers real questions.
Long-term rentals only
Like everywhere in California, an ADU cannot be rented for less than 31 days. It works for family or long-term tenants, not as a vacation rental.
California law, everywhere
The rules every city must respect
800 sq ft
Every city must allow at least an 800 sq ft detached ADU with 4 ft setbacks.
4 ft
Maximum side and rear setback for a new detached ADU.
750 sq ft
No impact fees up to this size.
60 days
To approve or deny a complete application, without a hearing.
Ideas for your lot
Plans that suit Costa Mesa lots
1 bedroom
One-bedroom with kitchen island
1 bed1 bath
2 bedrooms
Two bedrooms, two baths
2 beds2 baths
FAQ
ADU questions in Costa Mesa
Who approves an ADU in Costa Mesa?
The City of Costa Mesa, through Economic and Development Services.
Can my ADU have two floors?
Often yes, depending on your zone, with additional setbacks for the second floor. We check it on your parcel first.
Do you come to my property?
Yes. The visit is free: we look at the lot, the access and the utilities, then give you a realistic estimate.
Nearby areasNewport BeachHuntington BeachSanta Ana
Free feasibility call
Book a free 15-minute feasibility call
A project lead reviews your address, tells you what your lot can hold and gives you a first look at your financing eligibility.
What you get
- Free, with no obligation
- A clear answer on what your lot can hold
- A first look at financing eligibility, by phone or at your property
- A site visit only if it makes sense
Prefer to talk now? (424) 448-4895
Email: [email protected]
Los Angeles, CA · We come to your property
1 · Preferred time2 · Your property3 · Confirmed
Preferred day (Pacific time)
Preferred time
Tell us when to call you. A project lead calls you back at that time of day (Pacific time).
Your call is booked
We’ll confirm by text or phone. No obligation.
Service areas
Serving homeowners across Los Angeles
Los Angeles, the South Bay and Orange County, within about 40 miles of Paramount. Farther on request.
Service areas
ADU rules, city by city
Permits, fire and coastal zones, pre-approved plans: see what applies in the 36 cities we serve.
Central Los AngelesSan Fernando ValleyThousand OaksSimi ValleyParamountWest AdamsMid-CityCulver CityLong BeachDowneyWhittierNorwalkTorranceInglewoodComptonCarsonAnaheimSanta AnaIrvineHuntington BeachPasadenaGlendaleBurbankRialto (on request)Garden GroveOrangeFullertonCosta MesaNewport BeachTustinSherman OaksEncinoVan NuysWoodland HillsNorthridgeCalabasas