South San Francisco, San Mateo County

Room Addition Cost in South San Francisco, CA

South San Francisco remodeling costs are 20% abovethe California state average. Here's what a typical room addition costs in South San Francisco in 2026, based on a 300 sqf project.

Budget
$72,000
$240/sqf
Mid-Range
$126,000
$420/sqf
High-End
$198,000
$660/sqf

Cost breakdown

Foundation & Framing
30%$37,800
Roofing & Exterior
15%$18,900
Mechanical (HVAC, Electrical)
15%$18,900
Interior Finishes
20%$25,200
Windows & Doors
10%$12,600
Permits & Engineering
10%$12,600

Breakdown based on mid-range estimate of $126,000

Typical Timeline
3-6 months
Permits Required

Building permit, structural engineering, possibly zoning approval.

Remodeling in South San Francisco

Biotech corridor driving home values and renovation demand. Many mid-century homes being modernized. The city has streamlined ADU permitting to address housing demand.

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 South San Francisco

Kitchen Remodel
$36,000 – $108,000
Bathroom Remodel
$18,000 – $57,600
ADU / Guest House
$150,000 – $360,000
Roof Replacement
$15,000 – $45,000
Exterior Paint
$6,000 – $21,000
Whole House Remodel
$324,000 – $1,080,000

Room Addition cost in other California cities

Atherton
$84,000 – $231,000 | San Mateo County
Murrieta
$54,000 – $148,500 | Riverside County
Los Angeles
$63,000 – $173,250 | Los Angeles County
Sherman Oaks
$63,000 – $173,250 | Los Angeles County
Long Beach
$60,000 – $165,000 | Los Angeles County
Fairfax
$69,000 – $189,750 | Marin County
Union City
$66,000 – $181,500 | Alameda County
Ventura
$60,000 – $165,000 | Ventura County

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