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ADU builder in Costa Mesa, CA
Costa Mesa sits between the coast and the county’s job centers, with strong rental demand and its own ADU standards. We design to the current Costa Mesa code so plan check goes smoothly.
Coastal Orange County
Building an ADU in Costa Mesa.
What’s different about adding an ADU here, and how we plan around it.
Clear size and height rules
Costa Mesa allows detached ADUs up to 1,200 sq ft on single-family lots and 18 ft plus 2 ft for a matching roof pitch. Attached ADUs follow the underlying zone’s height and can be the greater of 50% of the house or 1,000 sq ft.
Placement on the lot
The city requires 6 ft between a detached ADU and the main house and other structures, so we plan the layout around separation as well as setbacks.
An ordinance that keeps evolving
The state reviewed Costa Mesa’s ADU ordinance in 2024 and required changes to match state law, so we always design to the current version of the code.
Plans that fit
Floor plans that work within Costa Mesa’s rules.
These ready-to-build plans fit Costa Mesa’s size, height limits. Our studio can adjust any of them to your lot.
Plan 400F
Studio · 1 Bath · 400 ft²
Plan 440
1 Bed · 1 Bath · 440 ft²
Plan 720
1 Bed · 1 Bath · 720 ft²
Plan 780
2 Bed · 1 Bath · 780 ft²
Plan 910
2 Bed · 1 Bath · 910 ft²
Plan 1000
3 Bed · 2 Bath · 1,000 ft²
How we work in Costa Mesa
One team from first visit to move-in.
01
Free ADU analysis
We review your Costa Mesa lot, what the local rules allow and which plans fit, with an estimated cost.
02
Design
Our in-house studio prepares construction-ready plans in about 1–2 months.
03
Permits
We submit to the City of Costa Mesa and handle every round of plan check.
04
Fixed-price build
Construction in about 4–5 months, managed by one project manager from our Long Beach office.
Costa Mesa ADU questions
Common questions in Costa Mesa.
How big can an ADU be in Costa Mesa?
On a single-family lot, a detached ADU can be up to 1,200 sq ft. On lots with an existing multi-family building, detached ADUs are 850 sq ft, or 1,000 sq ft with more than one bedroom.
How tall can an ADU be in Costa Mesa?
Detached ADUs can be 18 ft plus 2 ft for a roof pitch that matches the main house. Attached ADUs follow the zone’s height limit.
How far does an ADU need to be from the house in Costa Mesa?
Costa Mesa requires 6 ft of separation between a detached ADU and the main house and other structures.
Nearby
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Serving homeowners throughout Los Angeles and Orange County.