ADU Construction — Cost Guide
ADU Construction Cost in the San Francisco Bay Area
IronNest Construction — CSLB #1130134. Licensed general contractor serving San Francisco, the Bay Area, and Sacramento.
ADU Construction Cost in the San Francisco Bay Area
ADU costs in the Bay Area are among the highest in the country, driven by land costs, permit fees, and labor. That said, the rental income potential consistently exceeds the carrying cost of a construction loan — making most Bay Area ADU projects financially sound.
Project Scope
Typical Cost Range
JADU (Junior ADU, within existing space)
$40,000 – $100,000
Garage conversion (full ADU)
$120,000 – $220,000
Attached ADU addition
$160,000 – $300,000
Detached ADU (500–800 sq ft)
$180,000 – $320,000
Detached ADU (800–1,200 sq ft)
$260,000 – $450,000
ADU design and permits (no construction)
$15,000 – $40,000
What Affects the Price
- Unit size — every additional square foot adds cost
- Foundation type — slab vs. crawl space vs. basement
- Utility connections — new meter, sewer lateral, and gas connections
- Finishes — kitchen appliances, flooring, tile quality
- Site conditions — slope, access, tree removal
- Plan check fees — San Francisco charges among the highest in the state
Get a specific number for your project. Ranges are guides — your actual cost depends on your specific home, scope, and timeline. We give fixed-price proposals after a site visit.
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