Costa Mesa, Orange County

ADU / Guest House Cost in Costa Mesa, CA

Costa Mesa remodeling costs are nearthe California state average. Here's what a typical adu / guest house costs in Costa Mesa in 2026, based on a 500 sqf project.

Budget
$131,250
$263/sqf
Mid-Range
$210,000
$420/sqf
High-End
$315,000
$630/sqf

Cost breakdown

Foundation & Framing
25%$52,500
Mechanical (HVAC, Plumbing, Electrical)
20%$42,000
Interior Finishes
20%$42,000
Exterior & Roofing
15%$31,500
Kitchen & Bath Fixtures
10%$21,000
Permits, Plans & Engineering
10%$21,000

Breakdown based on mid-range estimate of $210,000

Typical Timeline
4-8 months
Permits Required

Building, electrical, plumbing, mechanical. May require plan check.

Remodeling in Costa Mesa

Central OC location with mix of affordable and premium neighborhoods. Eastside Costa Mesa has strong renovation potential. South Coast Metro area attracts higher-end projects.

California allows ADUs on most residential lots since 2020. An ADU adds living space and rental income. Cities must approve or deny within 60 days of a complete application.

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Other projects in Costa Mesa

Kitchen Remodel
$31,500 – $94,500
Bathroom Remodel
$15,750 – $50,400
Room Addition
$63,000 – $173,250
Roof Replacement
$13,125 – $39,375
Exterior Paint
$5,250 – $18,375
Whole House Remodel
$283,500 – $945,000

ADU / Guest House cost in other California cities

South San Francisco
$150,000 – $360,000 | San Mateo County
Santa Rosa
$137,500 – $330,000 | Sonoma County
Oakland
$150,000 – $360,000 | Alameda County
Folsom
$118,750 – $285,000 | Sacramento County
Campbell
$150,000 – $360,000 | Santa Clara County
Lake Forest
$131,250 – $315,000 | Orange County
Half Moon Bay
$150,000 – $360,000 | San Mateo County
Walnut Creek
$143,750 – $345,000 | Contra Costa County

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