Hillsborough, San Mateo County

ADU / Guest House Cost in Hillsborough, CA

Hillsborough remodeling costs are 40% abovethe California state average. Here's what a typical adu / guest house costs in Hillsborough in 2026, based on a 500 sqf project.

Budget
$175,000
$350/sqf
Mid-Range
$280,000
$560/sqf
High-End
$420,000
$840/sqf

Cost breakdown

Foundation & Framing
25%$70,000
Mechanical (HVAC, Plumbing, Electrical)
20%$56,000
Interior Finishes
20%$56,000
Exterior & Roofing
15%$42,000
Kitchen & Bath Fixtures
10%$28,000
Permits, Plans & Engineering
10%$28,000

Breakdown based on mid-range estimate of $280,000

Typical Timeline
4-8 months
Permits Required

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

Remodeling in Hillsborough

Exclusive residential town with large homes and strict architectural review. No commercial zones means all services come from outside. Expect top-tier contractor rates and extended design review timelines.

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 Hillsborough

Kitchen Remodel
$42,000 – $126,000
Bathroom Remodel
$21,000 – $67,200
Room Addition
$84,000 – $231,000
Roof Replacement
$17,500 – $52,500
Exterior Paint
$7,000 – $24,500
Whole House Remodel
$378,000 – $1,260,000

ADU / Guest House cost in other California cities

Elk Grove
$112,500 – $270,000 | Sacramento County
Corte Madera
$150,000 – $360,000 | Marin County
San Ramon
$143,750 – $345,000 | Contra Costa County
Woodland Hills
$131,250 – $315,000 | Los Angeles County
Novato
$143,750 – $345,000 | Marin County
Burlingame
$162,500 – $390,000 | San Mateo County
San Mateo
$156,250 – $375,000 | San Mateo County
Mission Viejo
$131,250 – $315,000 | Orange County

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