San Mateo, San Mateo County

ADU / Guest House Cost in San Mateo, CA

San Mateo remodeling costs are 25% abovethe California state average. Here's what a typical adu / guest house costs in San Mateo in 2026, based on a 500 sqf project.

Budget
$156,250
$313/sqf
Mid-Range
$250,000
$500/sqf
High-End
$375,000
$750/sqf

Cost breakdown

Foundation & Framing
25%$62,500
Mechanical (HVAC, Plumbing, Electrical)
20%$50,000
Interior Finishes
20%$50,000
Exterior & Roofing
15%$37,500
Kitchen & Bath Fixtures
10%$25,000
Permits, Plans & Engineering
10%$25,000

Breakdown based on mid-range estimate of $250,000

Typical Timeline
4-8 months
Permits Required

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

Remodeling in San Mateo

Central Peninsula location with strong remodeling demand. Mix of pre-war bungalows and mid-century ranches. The city's permitting department is moderately efficient by Bay Area standards.

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 San Mateo

Kitchen Remodel
$37,500 – $112,500
Bathroom Remodel
$18,750 – $60,000
Room Addition
$75,000 – $206,250
Roof Replacement
$15,625 – $46,875
Exterior Paint
$6,250 – $21,875
Whole House Remodel
$337,500 – $1,125,000

ADU / Guest House cost in other California cities

San Bernardino
$100,000 – $240,000 | San Bernardino County
Chula Vista
$118,750 – $285,000 | San Diego County
Calabasas
$143,750 – $345,000 | Los Angeles County
Culver City
$137,500 – $330,000 | Los Angeles County
Laguna Beach
$156,250 – $375,000 | Orange County
Roseville
$118,750 – $285,000 | Placer County
Sherman Oaks
$131,250 – $315,000 | Los Angeles County
Folsom
$118,750 – $285,000 | Sacramento County

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