Portola Valley, California

Zoning

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.

Building size

The maximum ADU you can build depends on the ADU type:

• The maximum size is 500 sq. ft. for a JADU
• Detached ADUs: 1,200 sq. ft. for lots < 3.5 acres. 1,500 sq. ft. for lots >= 3.5 acres
• Attached ADUs can be up to 1,700 sq. ft.

Building height

Height limitations for an ADU are those of the base zoning district. This includes daylight planes, where applicable. ADUs taller than eighteen feet (18’) vertical height or twenty-four feet (24’) maximum height, where allowed by the base zoning district, require Staff Discretionary Review from the town.

Setbacks

Minimum setbacks of 5 feet from the side and rear lot lines, as well as 6 feet from any existing structures are required for detached ADUs.

Parking

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

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.

Rental

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.

Watch-outs

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!

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