Accessory dwelling unit 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
These services cover the entire lifecycle of a backyard home, from initial property assessments to navigating local permit applications. You need this when you want to add living space but don't want to handle the complex zoning paperwork or design requirements yourself. Professionals guide you through the rules to ensure your project stays compliant with state and city codes while maximizing your property’s potential for rental income or housing family members.
Frequently asked in San Mateo
What is an ADU unit?
An ADU unit, or accessory dwelling unit, is a secondary housing unit on a single-family residential lot. It's a self-contained living space with its own kitchen, bathroom, and sleeping area. These units are designed for independent occupancy and can be attached to the main home or be a detached structure. They offer flexible housing solutions.
Are there ADU rules in New Hampshire?
While our services are focused locally, accessory dwelling unit rules vary significantly by location. New Hampshire has its own specific regulations for ADUs, which often differ from those in California. These rules might cover lot size, permitted locations, and design standards. For accurate information, you would need to consult New Hampshire's local ordinances.
Are there ADU rules in Massachusetts?
Our services are specific to the San Mateo area, but accessory dwelling unit regulations are indeed state and city dependent. Massachusetts has its own set of laws governing ADUs. These typically address aspects like minimum lot size, owner occupancy requirements, and maximum unit size. You'd need to consult local Massachusetts ordinances for precise details.
How do I get an ADU estimate?
Where can I find accessory dwelling unit builders near me?
Can I get an accessory dwelling unit for rent?
What is the accessory dwelling unit permit cost?
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: Downtown San Mateo, Bay Meadows, Shoreview, Aragon, Edgewater — and every surrounding area.
Areas we serve
Browse by state, then city.
California (4)
All of California · Rialto · San Buenaventura (Ventura) · San Mateo · Vacaville