Lafayette, Contra Costa County

Room Addition Cost in Lafayette, CA

Lafayette remodeling costs are 20% abovethe California state average. Here's what a typical room addition costs in Lafayette 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 Lafayette

Affluent Lamorinda community with established homes on larger lots. Premium finishes are the norm. Hillside lots may require additional engineering for additions.

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 Lafayette

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

Walnut Creek
$69,000 – $189,750 | Contra Costa County
Santa Monica
$72,000 – $198,000 | Los Angeles County
Hayward
$63,000 – $173,250 | Alameda County
Sonoma
$69,000 – $189,750 | Sonoma County
Union City
$66,000 – $181,500 | Alameda County
Petaluma
$66,000 – $181,500 | Sonoma County
Orinda
$75,000 – $206,250 | Contra Costa County
Huntington Beach
$66,000 – $181,500 | Orange County

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