Mill Valley, Marin County

ADU / Guest House Cost in Mill Valley, CA

Mill Valley remodeling costs are 30% abovethe California state average. Here's what a typical adu / guest house costs in Mill Valley in 2026, based on a 500 sqf project.

Budget
$162,500
$325/sqf
Mid-Range
$260,000
$520/sqf
High-End
$390,000
$780/sqf

Cost breakdown

Foundation & Framing
25%$65,000
Mechanical (HVAC, Plumbing, Electrical)
20%$52,000
Interior Finishes
20%$52,000
Exterior & Roofing
15%$39,000
Kitchen & Bath Fixtures
10%$26,000
Permits, Plans & Engineering
10%$26,000

Breakdown based on mid-range estimate of $260,000

Typical Timeline
4-8 months
Permits Required

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

Remodeling in Mill Valley

Affluent community at the base of Mount Tamalpais. Redwood-shaded hillside homes require specialized construction. Many older homes being renovated with premium finishes. Narrow roads can complicate material delivery.

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 Mill Valley

Kitchen Remodel
$39,000 – $117,000
Bathroom Remodel
$19,500 – $62,400
Room Addition
$78,000 – $214,500
Roof Replacement
$16,250 – $48,750
Exterior Paint
$6,500 – $22,750
Whole House Remodel
$351,000 – $1,170,000

ADU / Guest House cost in other California cities

Sunnyvale
$156,250 – $375,000 | Santa Clara County
Hermosa Beach
$150,000 – $360,000 | Los Angeles County
Benicia
$125,000 – $300,000 | Solano County
San Bernardino
$100,000 – $240,000 | San Bernardino County
San Luis Obispo
$131,250 – $315,000 | San Luis Obispo County
Half Moon Bay
$150,000 – $360,000 | San Mateo County
Los Altos
$168,750 – $405,000 | Santa Clara County
Roseville
$118,750 – $285,000 | Placer County

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