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All ADU Regulations

Los Altos, California

Los Altos, California ADU regulation is being updated to comply with new state laws. Learn about the new requirements for permitting an ADU is Los Altos.
Updated Jun 20, 2020


All properties zoned for single family and multifamily use may be eligible to build ADUs.

Number of units

Lots zoned for single family use that have an existing dwelling are permitted to add 1 ADU and 1 Jr. ADU (JADU).

Building size

Maximum square footage is determined by your ADU type:
  • 500 sq. ft. for a Jr. ADU (JADU)
  • 850 sq. ft. for studio / 1 bedroom ADUs
  • 1,000 sq. ft. for 2+ bedroom ADUs; ADUs larger than 850 sq. ft. may be subject to zoning clearance review for objective design standards
  • Attached ADUs may be no larger than than 50% of the floor area of the existing home

Building height

Detached ADUs can reach a maximum height of 16 feet. Attached ADUs can reach the same height as the main structure, assuming they comply with municipal code (including daylight plane).
Los Altos also has daylight plane provisions that might prevent you from building to the full 16 ft. close to your property line. The daylight plane starts at eight feet above the property line and slope in at a 6:12 roof pitch. Examples:
  • At 4 ft. from the property line the max height would be 10 ft.
  • At 10 ft. from the property line the max height would be 16 ft.


Conversion of existing unfinished basement space can be used for an attached ADU.


Minimum setbacks of 4 feet from the side and rear lot lines, as well as 6 feet from any existing structures are required for detached ADUs.


No additional parking is required for ADUs if they are within 0.5 miles of public transportation (a bus stop, train station, etc.). When converting a garage or carport, replacement parking is not required.


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.


While long-term rentals are permitted for ADUs, short-term rentals (e.g. Airbnb for less than 30 days) are not permitted in Santa Clara.


Do you have a utility easement over your property? Do you have special setbacks? Reach out to us and we’ll help you build a custom ADU to fit your unique property characteristics and local regulations!

Want to learn more about ADU regulations in your area?

Book a free consultation and estimate with a Cottage ADU Expert to find out what’s possible on your property!