ADU Builder in Millbrae, CA
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Millbrae ADUs
ADU permits in Millbrae go through the Building Division with ministerial approval. Under the City’s posted ordinance, JADUs are up to 500 sq ft and an 800 sq ft, 16-foot ADU with 4-foot setbacks is always allowed. ADUs under 750 sq ft are exempt from impact fees, those over 500 sq ft pay school fees, and the City runs a pre-approved ADU program. Millbrae’s posted ordinance dates from 2020, so we confirm current limits under state law for each project. An ADU does not need sprinklers if the main house does not have them.
ADU Construction
Permits
Sewer lateral: added plumbing fixtures or work on 25% or more of the structure starts with an Engineering determination and a video inspection of the sewer lateral.
Before final: a Waste Management Plan final summary showing 65% diversion must be approved before the final inspection can be scheduled. Construction hours: 7:30 a.m. to 7 p.m. weekdays, 8 a.m. to 6 p.m. Saturdays, 9 a.m. to 6 p.m. Sundays and holidays.
621 Magnolia Avenue, Millbrae, CA 94030
Building (650) 259-2330 · Planning (650) 259-2341 · Engineering (650) 259-2339
All building permits go through the City’s online portal (eProcess360); paper applications are not accepted. Inspections are scheduled by email to the Permit Technician or at (650) 259-2330, at least a day ahead. Posted counter and inspection hours vary between City pages, so call ahead.
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Other Millbrae services: Bathrooms · Kitchens · Additions · New Homes · Millbrae overview
Same service nearby: Burlingame · San Bruno · Hillsborough
See how to build an ADU.
Millbrae ADU Builder FAQ
Is ADU approval ministerial in Millbrae?
Yes.
Does Millbrae have pre-approved ADU plans?
Yes, through its pre-approved ADU program.
Do ADUs pay school fees?
ADUs over 500 sq ft do.
Does the ADU need sprinklers?
Not if the main house does not have them.