Table of Contents

• ADUs/JADUs AND THEIR BENEFITS
• QUICK OVERVIEW: TOWN ADU REQUIREMENTS
• QUICK OVERVIEW: HOW TO BUILD AN ADU/JADU IN TOWN
• FREQUENTLY ASKED QUESTIONS 
• CONTACT INFORMATION AND ADDITIONAL RESOURCES
• TAKE THE SURVEY ( BY JANUARY 18, 2023 )

QUICK OVERVIEW: TOWN ADU REQUIREMENTS

For detailed Municipal Code information, see Section 18.36.040.B

SIZE:

JADU: Up to 500 sq ft

Internal ADU: Up to 1,200 sq ft (or up to 1,700 sq ft with discretionary review)

External ADU (conforming to Town standards for setbacks/etc., <3.5 acres): Up to 1,200 sq ft

External ADU (conforming to Town standards for setbacks/etc., >3.5 acres): Up to 1,500 sq ft

External ADU (not conforming to Town standards): 850 sq ft (studio/1BR); 1,000 sq ft (2+BR)

SETBACKS:

Properties <1 acre: 20' front, 10' sides/rear (Town standards), 4' sides/rear (State standards)

Properties >1 acre: 50' front, 20' sides/rear (Town standards), 4' sides/rear (State standards)

Note that other requirements apply if the project uses the State standards rather than Town standards.

NUMBER OF UNITS ALLOWED:

Properties <3.5 acres: (1 External or 1 Internal ADU) + (1 JADU) = 2 units total

Properties >3.5 acres: (1 Detached ADU) + (1 Internal ADU) + (1 JADU) = 3 units total

PARKING:  External ADUs require one off-street parking space that can be uncovered, in tandem with other parking, and/or in setbacks. For properties >1 acre where the ADU is under 1,200 sq ft the parking space may overlap with guest parking. Internal ADUs/JADUs do not require a dedicated parking space.

SEWER/SEPTIC CONSIDERATIONS: Properties considering adding an ADU or JADU should carefully consider their sewer or septic system. Your system will need to have available capacity to serve your new unit, in particular if a bedroom is added. This may involve a simple hookup to an existing system, or could involve large costs with expanding a septic system or extending to a street sewer system. If on sewer, you will need an additional hook-up for an external ADU.

ELECTRICAL UTILITIES: 

Attached/Internal ADU/JADU - no undergrounding required

Detached ADU - if connection is from main house, required to underground from main house

SAFETY RESTRICTIONS:

FIRE:  Certain parcels in Portola Valley may be restricted in development due to fire safety issues, such as street ingress/egress, slope, width of road and other conditions.

GEOLOGIC:  Certain parcels may be restricted in development under the Town’s geologic regulations, with respect to proximity to earthquake faults, traces and areas subject to active downslope movement as shown on the Town’s Geologic and Ground Movement Potential Maps.

COST CONSIDERATIONS: Costs vary widely for construction in the Bay Area. On average, it costs between $600 to $1,000 per square foot to construct a unit in Town.  Town permitting fees are usually a minor component of a new construction project, for example:

800 square foot detached ADU

Property on sewer

Planning & Building Permit Fees: $9,449

Sewer Fees: $4,370

TOTAL: $13,819

CONVERSIONS: Conversions represent a potentially much more affordable way of creating an ADU or JADU on your property. A room in your home could be converted into a JADU with the addition of a bathroom, a simple efficiency kitchen, and an exterior door. A conversion that does not include a bathroom must include an interior door to access shared bathroom facilities. A previously permitted pool house could be converted into an ADU with the addition of a kitchen and/or bath.