Adu housing — 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.

About this service

ADU housing refers to the creation of independent living quarters on the same lot as a primary residence. This includes everything from detached backyard cottages to converted garages or above-garage apartments. You need this if you are looking to increase the value of your property, generate rental income, or provide long-term housing for guests. It is an effective way to maximize your land use while maintaining the character of your existing home and neighborhood environment.

Frequently asked in San Mateo

Also serving nearby: Hayward · Daly City · Oakland · Sunnyvale · Fremont

All cities in California →

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: Bay Meadows, Central San Mateo, Edgewater, Hillsdale, Shoreview, Uplands — and every surrounding area.