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ADU Builders & Contractors in Costa Mesa, CA

Costa Mesa has launched a Safe ADU Legalization Program under AB 2533 to help homeowners with unpermitted units come into compliance, alongside streamlined permitting for new ADU construction.

📊 ADU Quick Facts for Costa Mesa

Avg. Cost/sqft

$300-$550

Permit Timeline

4-10 weeks

Max Size

1200 sqft

Setbacks

4ft sides

View Costa Mesa Planning Department →

Top 426 ADU Contractors in Costa Mesa

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#1SEACREST DEVELOPERS INC

Costa Mesa, CA

Seacrest Developers Inc — licensed ADU contractor in Costa Mesa, CA. Detached ADU construction. 24+ years experience.

View Profile📞 (949) 499 1381
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#2KINSER CAPITAL

Costa Mesa, CA

Kinser Capital — licensed ADU contractor in Costa Mesa, CA. Detached ADU construction.

View Profile📞 (916) 420 9983
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#3GREEN GLOBE PLUMBING

Costa Mesa, CA

Green Globe Plumbing — licensed ADU contractor in Costa Mesa, CA. Detached ADU construction. 14+ years experience.

View Profile📞 (949) 290 7126
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#4WESTBERG TILES

Costa Mesa, CA

Westberg Tiles — licensed ADU contractor in Costa Mesa, CA. Detached ADU construction. 21+ years experience.

View Profile📞 (714) 658 2499
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#5EPIC CUSTOM HOMES INC

Costa Mesa, CA

Epic Custom Homes Inc — licensed ADU contractor in Costa Mesa, CA. Detached ADU construction. 9+ years experience.

View Profile📞 (949) 280 7006
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#6OPTIMA CONSTRUCTION INC

Costa Mesa, CA

Optima Construction Inc — licensed ADU contractor in Costa Mesa, CA. Detached ADU construction. 8+ years experience.

View Profile📞 (949) 394 3870
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#7KEUSDER WALTER WESTON

Costa Mesa, CA

Keusder Walter Weston — licensed ADU contractor in Costa Mesa, CA. Detached ADU construction. 42+ years experience.

View Profile📞 (714) 557 9003
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#8BEACHWOOD CONSTRUCTION

Costa Mesa, CA

Beachwood Construction — licensed ADU contractor in Costa Mesa, CA. Detached ADU construction. 41+ years experience.

View Profile📞 (949) 230 1548
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#9CALIFORNIA PROPERTY STANDARDS

Costa Mesa, CA

California Property Standards — licensed ADU contractor in Costa Mesa, CA. Detached ADU construction.

View Profile📞 (949) 278 4343
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#10R D M S INC

Costa Mesa, CA

R D M S Inc — licensed ADU contractor in Costa Mesa, CA. Detached ADU construction. 23+ years experience.

View Profile📞 (714) 546 1130
View All 426 Contractors →

💰 How Much Does an ADU Cost in Costa Mesa?

Garage Conversion

$75,000 - $185,000

Converting existing garage to living space

Detached ADU

$150,000 - $380,000

New standalone unit (600-1,200 sqft)

Permit & Fees

$4,000 - $12,000

Plan check, permits, utility connections

* Costs vary based on size, finishes, site conditions, and contractor. Get quotes from multiple Costa Mesa contractors to compare pricing.

❓ Frequently Asked Questions About ADUs in Costa Mesa

How much does it cost to build an ADU in Costa Mesa?▼
The average cost to build an ADU in Costa Mesa ranges from $150,000 to $380,000, or approximately $300 to $550 per square foot. Garage conversions typically cost $75,000 to $185,000.
How long does it take to get an ADU permit in Costa Mesa?▼
The ADU permit process in Costa Mesa typically takes 4 to 10 weeks. California law requires cities to approve or deny ADU permits within 60 days of receiving a complete application.
What are the ADU size limits in Costa Mesa?▼
In Costa Mesa, detached ADUs can be up to 1200 square feet. Attached ADUs are limited to 50% of the primary dwelling or 1,200 sqft, whichever is less. Junior ADUs (JADUs) are limited to 500 sqft and must be within the existing home.
What is the setback requirement for ADUs in Costa Mesa?▼
Costa Mesa requires 4-foot setbacks from side property lines and 4-foot setbacks from rear property lines for new ADU construction. Converted structures (like existing garages) may maintain their current setbacks.
Do I need to provide parking for my ADU in Costa Mesa?▼
No parking is required for ADUs in Costa Mesa if your property is within half a mile of public transit, in a historic district, part of an existing multi-family building, or if the ADU is a garage conversion. Otherwise, one space may be required.

Also See ADU Contractors In

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