Fairfax, Marin County

ADU / Guest House Cost in Fairfax, CA

Fairfax remodeling costs are 15% abovethe California state average. Here's what a typical adu / guest house costs in Fairfax 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 Fairfax

Bohemian Marin community with the most affordable housing in central Marin. Older, smaller homes with strong renovation potential. Hillside lots can complicate additions.

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 Fairfax

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

Belmont
$156,250 – $375,000 | San Mateo County
Murrieta
$112,500 – $270,000 | Riverside County
Modesto
$100,000 – $240,000 | Stanislaus County
Visalia
$93,750 – $225,000 | Tulare County
Santa Rosa
$137,500 – $330,000 | Sonoma County
Newark
$137,500 – $330,000 | Alameda County
Corte Madera
$150,000 – $360,000 | Marin County
Santa Barbara
$150,000 – $360,000 | Santa Barbara County

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