Sonoma, Sonoma County

ADU / Guest House Cost in Sonoma, CA

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

Historic town with strict design guidelines around the Plaza. Wine country aesthetics - natural stone, exposed beams, indoor-outdoor living - drive material costs higher. Limited contractor pool in this small market.

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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