Home Additions in Hillsborough, CA
Get a Free Hillsborough Addition Consultation
ADRB Review and Story Poles
Design review: every exterior change in Hillsborough needs design review. Staff reviews minor projects; the five-member Architecture and Design Review Board (ADRB), which meets the first Monday of each month, reviews new homes and substantial additions, and new houses, major remodels and teardowns start with an ADRB preliminary review. A pre-application meeting is required, board members visit the site, and the Town mails notice to owners within 500 feet 15 days before the hearing.
Story poles are required for ADRB projects 22 feet tall or more, new two-story homes and second-story additions. They go up at least 10 business days before the hearing, are certified within 5 days, and stay up through the 15-day appeal period.
Addition Work
Floor Area, Sprinklers and Trees
Floor area and envelope: maximum floor area is 25% of net lot area for the first acre plus 15% beyond that. Height is capped at 32 feet, with a building envelope rising 22 feet at the setback line and then sloping at 45 degrees. Setbacks are 20 feet at interior lot lines and 25 to 30 feet along streets, and the ADRB can find a home too massive even below the maximum.
Fire sprinklers: required in all new homes, and in existing homes over 2,000 sq ft (or over two stories) when added or altered area exceeds 1,500 sq ft, or 20% for homes over 7,500 sq ft, counted over 2 years. A room counts as altered when half or more of its wall or ceiling finishes are replaced. Central County Fire, 1399 Rollins Road, Burlingame, issues sprinkler permits.
Trees: any tree 18 inches or more in diameter at 4½ feet is protected. Removals tied to development go through design review first, with an arborist report and replanting plan.
A soils report is required for most two-story additions, and additions over 500 sq ft pay Hillsborough City School District fees.
1600 Floribunda Avenue, Hillsborough, CA 94010 · Town Hall (650) 375-7400
Building (650) 375-7411, pl*******@**********gh.net · Planning (650) 375-7422 (planners by appointment) · Engineering (650) 375-7444
Applications are electronic through eTRAKiT, and contractors register with their CSLB license. Inspections are requested by phone at (650) 375-7411 at least two to three days ahead; inspectors will not inspect work by subcontractors who are not on the subcontractor list or lack a Town business license. Hours vary, so call ahead.
Explore More
Other Hillsborough services: ADUs · Bathrooms · Kitchens · New Homes · Hillsborough overview
Same service nearby: Burlingame · San Mateo · Belmont
Hillsborough Home Additions FAQ
Does a second-story addition need story poles?
Yes, except some under 500 sq ft not facing a street may be reviewed by staff.
How large can a Hillsborough home be?
25% of net lot area for the first acre plus 15% beyond.
How far does notice reach?
Owners within 500 feet, 15 days before the hearing.
When does the ADRB meet?
The first Monday of each month.