Backyard accessory dwelling unit — San Mateo, CA
Last updated: September 24, 2026
What affects the price
Building an ADU involves several moving parts that shape your total budget. The biggest factor is whether you choose a prefabricated unit or a custom build on-site. Site preparation is also significant; if your land requires extensive grading, utility trenching, or foundation work, costs will climb. Your choice of finishes—like kitchen cabinetry, flooring, and siding materials—also shifts the bottom line. We help you navigate these variables to find a setup that fits your property. Exact pricing confirmed free on the call.
Frequently asked in San Mateo
What is the ADU cost in San Mateo?
Can I get a 24-hour ADU estimate in San Mateo?
What are the benefits of homes with in-law suites in San Mateo?
Are accessory dwelling units allowed in San Mateo?
What is the accessory dwelling unit construction cost in San Mateo?
How do I find an affordable accessory dwelling unit in San Mateo?
What's involved in accessory dwelling unit homes in San Mateo?
Also serving nearby: Hayward · Daly City · Oakland · Sunnyvale · Fremont
More on this: HUD ADU resources — ADU policy and financing research.
Service area details
Serving all of San Mateo — population 101,327; about 8,350 residents per square mile across 12.1 sq mi. ZIP codes covered include 94401, 94402, 94403, 94404, 94497.
Neighborhoods served in San Mateo: Aragon, Bay Meadows, Edgewater, Laurel Creek, Shoreview — and every surrounding area.
Areas we serve
Browse by state, then city.
California (4)
All of California · Rialto · San Buenaventura (Ventura) · San Mateo · Vacaville