Town of Los Altos Hills - Santa Clara ADU

Wondering if your community has pre-approved ADU plans? See more details here

Wondering if your community has pre-approved ADU plans? See more details here

A project of the Santa Clara County Planning Collaborative

Home > Local Rules > Town of Los Altos Hills

Local ADU Rules

Town of Los Altos Hills

Last Updated September 30, 2025

ADU Contact:

Phone: (650) 947-2544

Planning Division email: planning@losaltoshills.ca.gov

General Information	Details
ADU resources	https://www.losaltoshills.ca.gov/494/Accessory-Dwelling-Units
Pre-Approved Plans
Planning	Email: planning@losaltoshills.ca.gov Website: https://www.losaltoshills.ca.gov/178/Planning-Department
Building	Email: building@losaltoshills.ca.gov Website: https://www.losaltoshills.ca.gov/292/Building-Department
School District	Los Altos School District Impact Fees https://www.lasdschools.org/District/Department/147-Business-Services Mountain View Los Altos Union High School District Impact Fees www.mvla.net Palo Alto Unified School District School Impact Fees www.pausd.org
Utilities	PG&E https://www.pge.com/en_US/small-medium-business/building-and-property/building-and-maintenance/building-and-renovation.page Valley Water, Purissima Hills Water District, California Water Service Company https://www.valleywater.org/accordion/los-altos-hills Public Sewer/Private Sewer Connection – Los Altos Hills Public Works Department http://www.losaltoshills.ca.gov/197/Public-Works-Engineering Private Septic System https://ehinfo.sccgov.org/home GreenWaste https://www.greenwaste.com/los-altos-hills/
County Departments	Santa Clara County Office of the Clerk-Recorder https://clerkrecorder.sccgov.org/home Santa Clara County Fire District https://www.sccfd.org/ County Department of Environmental Health (if the property is not connected to sewer) https://cpd.sccgov.org/programs-and-services/land-use-program-onsite-wastewater-treatment-systems
ADU Ordinance	Los Altos Hills Municipal Code, Article 14 https://library.qcode.us/lib/los_altos_hills_ca/pub/municipal_code/item/title_10-chapter_1-article_14?view=all

Standards and Rules	Details
Process Overview	One mandatory pre-application meeting with a planner with a fee of $410, then submit a Building Permit Application See the Los Altos Hills ADU website for more information: https://www.losaltoshills.ca.gov/494/Accessory-Dwelling-Units
Zones allowed	R-A
Minimum ADU Size	150 square feet
Maximum ADU Size	1000 square feet maximum if the ADU is built 4 feet from the side and rear property lines 1200 square feet maximum if the ADU meets the standard 30-foot rear and side setbacks The maximum size of a detached accessory dwelling unit that is a studio or with one bedroom is eight hundred fifty (850) square feet The maximum size of an accessory dwelling unit with more than one bedroom is one thousand (1,000) square feet The maximum size of an attached accessory dwelling unit is one thousand (1,000) square feet or fifty (50) percent of the primary dwelling’s living area, whichever is less, provided that at least eight hundred (800) square feet is allowed The maximum size for a Junior ADU is 500 square feet, unless it includes one additional on-site parking space, in which case the maximum size may be increased to 650 square feet
Number of ADUs/Bedrooms
Maximum ADU Height	Maximum ADU height is 16 feet if the ADU is built 4 feet from rear and side property lines Maximum height increases to 19 feet if the ADU is built 30 feet (standard setbacks) from the rear and side property lines A detached ADU can have a second story as long as it meets standard height requirements An attached ADU can reach a maximum of the same height as a primary dwelling (27 feet) if it meets the standard setbacks (30 feet)
Setbacks	For ADUs up to 1000 square feet setbacks must be 4 feet from the side and rear property lines For ADUs up to 1200 square feet both rear and side setbacks must be 30-foot There are no special setbacks for corner lots There is no minimum / maximum distance required between the primary residence and ADU
Lot or Location Restrictions	Up to 800 sq ft floor area and development area are exempted for an ADU The maximum floor area and development area (paved area) of the parcel are calculated by formula
Parking Requirements	JADUs: No parking required ADUs: One spot required unless: Within one-half mile walking distance of public transit Within one block of a car share vehicle On a street where on-street parking permits are required but not offered to the occupant of the ADU Built as part of a new home
Other Requirements
Owner Occupancy	JADUs: Owner must occupy either the JADU or the primary house
Deed Restrictions	None
Renting Regulations	An ADU or JADU must be rented for a period of no less than thirty-one (31) days, and cannot be occupied as a short-term rental unit
Departments and Agencies Involved in Permitting	Planning, Building, Engineering, the County Fire Department, the County Department of Environmental Health (if the property is not connected to sewer), and Geotechnical Review (if the property is in a geo hazard zone)
Fees for ADUs	Planning, Building, Engineering, the County Fire Department, the County Department of Environmental Health (if the property is not connected to sewer), and Geotechnical Review (if the property is in a geo hazard zone) Planning Pre-Application Review Meeting = $410 Building Permit Fee = $240+0.9% of project evaluation ADUs are not subject to City impact fees. ADUs may still be subject to impact fees assessed by non-City public agencies, such as School District fees or Fire District fees.
Sample Fees From Recently Built Projects

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