Hillsborough ADU topic page
Hillsborough ADU Rules
Start with the official local ADU rules, then confirm lot-specific limits before requesting provider quotes.
Short answer
Start with the official local ADU rules, then confirm lot-specific limits before requesting provider quotes.
Source requirement: Official city or county rule source parsed and cited.
Local rule evidence
Size
JADU: 500 sq. ft. Building Permit Only: 800 sq. ft. Detached/Attached ADU Planning Permit (one bedroom or less): 850 sq. ft. Detached/Attached ADU Planning Permit (2+ bedrooms): 1,000 sq. ft. Applicant can request an ADU Exception Review, which allows more permissive...
Setbacks and parking
Side and Rear: 4 feet Front: 25 feet, unless these would preclude the construction of an ADU that is 800 square feet No setback is required for an ADU that is constructed in the same location and to the same dimensions as an existing structure JADUs: No parking...