Walnut Creek, Contra Costa County

ADU / Guest House Cost in Walnut Creek, CA

Walnut Creek remodeling costs are 15% abovethe California state average. Here's what a typical adu / guest house costs in Walnut Creek in 2026, based on a 500 sqf project.

Budget
$143,750
$288/sqf
Mid-Range
$230,000
$460/sqf
High-End
$345,000
$690/sqf

Cost breakdown

Foundation & Framing
25%$57,500
Mechanical (HVAC, Plumbing, Electrical)
20%$46,000
Interior Finishes
20%$46,000
Exterior & Roofing
15%$34,500
Kitchen & Bath Fixtures
10%$23,000
Permits, Plans & Engineering
10%$23,000

Breakdown based on mid-range estimate of $230,000

Typical Timeline
4-8 months
Permits Required

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

Remodeling in Walnut Creek

Affluent East Bay suburb with active remodeling market. Mix of condos and single-family homes. Hot summers drive demand for energy-efficient windows and HVAC upgrades.

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 Walnut Creek

Kitchen Remodel
$34,500 – $103,500
Bathroom Remodel
$17,250 – $55,200
Room Addition
$69,000 – $189,750
Roof Replacement
$14,375 – $43,125
Exterior Paint
$5,750 – $20,125
Whole House Remodel
$310,500 – $1,035,000

ADU / Guest House cost in other California cities

Oakland
$150,000 – $360,000 | Alameda County
Stockton
$106,250 – $255,000 | San Joaquin County
Redwood City
$156,250 – $375,000 | San Mateo County
Danville
$150,000 – $360,000 | Contra Costa County
Pleasanton
$143,750 – $345,000 | Alameda County
Millbrae
$150,000 – $360,000 | San Mateo County
Brentwood
$125,000 – $300,000 | Contra Costa County
Saratoga
$168,750 – $405,000 | Santa Clara County

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