Question 1

Do I need a permit to build an ADU in San Mateo?

Accepted Answer

Yes. Every ADU requires a building permit, but California's statewide ADU law makes approval ministerial (by-right) for compliant projects — no public hearing and a 60-day decision. We prepare the full permit set and manage the City of San Mateo / San Mateo County submittal for you.

Question 2

How much does an ADU cost in San Mateo?

Accepted Answer

It depends on the type. Garage conversions typically run $110,000-$200,000, junior ADUs $45,000-$95,000, and new detached ADUs $230,000-$450,000 turnkey. We give you a clear fixed-scope estimate after reviewing your lot and goals — free of charge.

Question 3

How long does it take to build an ADU?

Accepted Answer

A junior ADU or garage conversion can be done in 2-5 months, while a ground-up detached or prefab ADU generally takes 4-10 months including design and permitting. We give you a milestone schedule before construction starts.

Question 4

Can I rent out my ADU?

Accepted Answer

Yes. ADUs and junior ADUs can be rented on 30-day-plus leases throughout San Mateo County, making them a strong source of rental income. Short-term (under 30 day) rentals are generally restricted.

Question 5

How big can my ADU be?

Accepted Answer

California allows detached ADUs up to 1,200 sq ft, junior ADUs up to 500 sq ft, and cities must allow at least 800 sq ft regardless of lot coverage limits. Your exact maximum depends on your lot — we confirm it during feasibility.

Question 6

Do I have to add parking for my ADU?

Accepted Answer

Often no. If your property is within half a mile of transit — which covers much of San Mateo — or you're converting an existing garage, state law waives the added-parking requirement.

Question 7

Are you licensed and insured?

Accepted Answer

Yes. We are a fully licensed California general contractor carrying general liability and workers' compensation coverage, so your project and property are protected from permit to final inspection.

Question 8

Do you offer free estimates?

Accepted Answer

Absolutely. We provide free, no-obligation estimates for every ADU, garage conversion, and addition. Text or call us and we'll review your project and get you a clear scope and price.

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