All properties zoned for single family, two-family or multifamily may be eligible to build ADUs.
Number of units
The number of ADUs you’re able to build depends on how your lot is zoned:
- Lots zoned for single family use may add 1 ADU and 1 Jr. ADU (JADU).
- Lots zoned for two-family or multi-family may add up to 2 detached ADUs per lot or up to 25% of the existing units in the building if conversions of existing non-living space.
The maximum ADU you can build depends on the ADU type:
- The maximum size is 500 sq. ft. for a JADU
- 850 sq. ft. for a one bedroom detached ADU
- 1,000 sq. ft. for a 2 bedroom detached ADU
- Attached ADUs can be 1,000 sq. ft. or 50% of the existing area of the primary dwelling, whichever is greater.
- Existing conversions are not subject to size maxes.
Detached ADUs can reach a maximum height of 1 story or 16 ft with 9 ft max plate height. For attached ADUs, the maximum height is the same as underlying zone.
Minimum setbacks of 4 feet from the side and rear lot lines, as well as 10 feet from any existing structures are required for detached ADUs. However, for detached ADUs, there are no setbacks if ADU is located in rear 40% of lot. For attached ADUs: 4 ft from side & rear property lines minimum apply.
One parking spot required unless any of the following true:
- The accessory dwelling unit is located within one-half mile walking distance of public transit.
- The accessory dwelling unit is located within an architecturally and historically significant historic district.
- The accessory dwelling unit is part of the proposed or existing primary residence or an accessory structure.
- When on-street parking permits are required but not offered to the occupant of the accessory dwelling unit.
- When there is a car share vehicle located within one block of the accessory dwelling unit.
Owner occupancy is not a requirement for permitting an ADU from January 1, 2020 until January 1, 2025. This is a great opportunity for rental property owners to increase their yields in a cost-effective way.
A deed restriction prohibiting the separate sale of the units on the property will be required to be notarized and recorded with the San Mateo County Assessor’s Office (prior to issuance of a building permit) once an ADU application is approved by the Planning Division.
While long-term rentals are permitted for ADUs, short-term rentals (e.g. Airbnb for less than 30 days) are not permitted in the city.
Are you in a creek protection area? Do you have a utility easement over your property? Reach out to us and we’ll help you build a custom ADU to fit your unique property characteristics and local regulations!