ADU Builders in San Mateo, California
Whether you want a rental unit, a home for aging parents or a studio for adult kids, building an ADU in San Mateo has never been easier under California's ADU laws. Our team plans every project around the cool microclimates, fog belts and seismic activity typical of San Mateo.
Typical cost
$250k–$520k
Permit time
6–10 weeks
Est. rent
$2,600+/mo
Population
103,000
Popular ADU types in San Mateo
Our most requested projects in San Mateo are garage conversions and junior ADUs (JADUs). Many San Mateo parcels built between the 1950s and 1980s have wide rear yards that fit an 800–1,200 sq ft detached unit without touching the main house.
Design-wise, San Mateo homeowners in the Bay Area tend to favor compact, light-filled modern designs that maximize small urban lots.
Building an ADU in San Mateo County
Every San Mateo ADU we build is engineered around local conditions — especially seismic engineering, sewer lateral rules and high labor costs. We prepare complete plan sets so the city can approve within the state's 60-day review window, typically 6–10 weeks here.
At $2,600–$4,200 per month in rent, a new ADU in San Mateo can pay for itself in roughly 9.4 years.
San Mateo ADU FAQs
How much does it cost to build an ADU in San Mateo?
Most San Mateo ADUs we build land between $250k and $520k, depending on size, site work and finishes. Garage conversions sit at the low end; custom two-story units at the high end.
How long does ADU permitting take in San Mateo?
State law requires cities to act on complete ADU applications within 60 days. In practice, San Mateo permits typically take 6–10 weeks when plans are submitted complete — which is what our in-house drafting team focuses on.
What can I rent an ADU for in San Mateo?
Based on Bay Area rental trends, a new 1-bedroom ADU in San Mateo commonly rents for $2,600–$4,200 per month, putting typical payback around 9.4 years.
What are the biggest challenges for ADUs in San Mateo?
In San Mateo and the wider Bay Area, the issues we plan around most are seismic engineering, sewer lateral rules and high labor costs. We review these during a free feasibility check before you commit.
Is garage conversions a good option in San Mateo?
Yes — garage conversions are among the most popular projects we build in San Mateo. Newer subdivisions in San Mateo often have tighter side yards, so we frequently recommend attached ADUs or converting an existing garage to keep costs down.
ADU builders near San Mateo
Get a free ADU feasibility check in San Mateo
Tell us about your lot. We'll review zoning, setbacks and utilities and send a ballpark budget — no obligation.