San Jose, Santa Clara County

Room Addition Cost in San Jose, CA

San Jose remodeling costs are 25% abovethe California state average. Here's what a typical room addition costs in San Jose in 2026, based on a 300 sqf project.

Budget
$75,000
$250/sqf
Mid-Range
$131,250
$438/sqf
High-End
$206,250
$688/sqf

Cost breakdown

Foundation & Framing
30%$39,375
Roofing & Exterior
15%$19,688
Mechanical (HVAC, Electrical)
15%$19,688
Interior Finishes
20%$26,250
Windows & Doors
10%$13,125
Permits & Engineering
10%$13,125

Breakdown based on mid-range estimate of $131,250

Typical Timeline
3-6 months
Permits Required

Building permit, structural engineering, possibly zoning approval.

Remodeling in San Jose

Silicon Valley incomes drive premium pricing. ADU construction is extremely popular as homeowners add rental units. The city has one of the most streamlined ADU permitting processes in the state.

A room addition adds square footage and value to your home. Costs depend on whether it's a simple bump-out, a second story, or a full wing addition with plumbing.

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Other projects in San Jose

Kitchen Remodel
$37,500 – $112,500
Bathroom Remodel
$18,750 – $60,000
ADU / Guest House
$156,250 – $375,000
Roof Replacement
$15,625 – $46,875
Exterior Paint
$6,250 – $21,875
Whole House Remodel
$337,500 – $1,125,000

Room Addition cost in other California cities

San Anselmo
$72,000 – $198,000 | Marin County
Los Angeles
$63,000 – $173,250 | Los Angeles County
Poway
$60,000 – $165,000 | San Diego County
Newport Beach
$75,000 – $206,250 | Orange County
Laguna Beach
$75,000 – $206,250 | Orange County
Encino
$66,000 – $181,500 | Los Angeles County
Union City
$66,000 – $181,500 | Alameda County
Costa Mesa
$63,000 – $173,250 | Orange County

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