Adu services — 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 services manage the technical and creative side of building a secondary unit on your lot. Whether you are converting a garage or building a new structure from the ground up, you need these services to bridge the gap between architectural plans and physical construction. They help manage site preparation, utility connections, and structural integrity, ensuring your project is ready for occupancy without you having to coordinate multiple subcontractors independently.

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: Aragon, Bay Meadows, Shoreline, Polhemus — and every surrounding area.