Los Altos, CA

Accessory Dwelling Unit (ADU) City Guidelines


Attached/Detached: R1-10/R1-H/R1-20/R1-40/R3-4.5/R3-5/R3-3/R3.1.8/R3-1

(Note: ADUs are exempt from standards requirements if the unit: (a) is one ADU per single family lot located within R1-10, R1-H, R1-20, or R1-40 zones; (b) is contained within the existing space of the main dwelling or an existing accessory structure; (c) has independent exterior access from the main dwelling; (d) has side and rear setbacks sufficient for fire safety.)

Lot Size:

No minimum.

Maximum ADU Floor Area:

Attached: 1,200 sq.ft. and not more than 50% of living area

Detached: 1,200 sq.ft. and not more than 50% of living area

No. of Bedrooms:  


Storage / Closet:

No min/max

Kitchen / Bath:  

Require separate bathroom and kitchen facilities (permanent range, counters, refrigerator, sink). Min. 1 bathroom.


ADU must have one parking space per unit or per bedroom, whichever is less. No parking standards shall be imposed on an ADU that is: (a) located within one-half mile of a public transit stop or station, (b) located within an architecturally and historically significant historic district, (c) is part of the proposed or existing primary dwelling or an existing accessory structure, (d) not offered on-street parking permits, (e) within one block of a car share vehicle.


Attached/Detached: must comply with minimum requirements of underlying zone.

No setbacks are required for an existing garage partially or fully converted to an ADU.

For an ADU constructed above an existing garage, a minimum of 5’ shall be required from side and rear lot lines.


Attached/Detached: must comply with standards of underlying zoning district.


ADU cannot face the street.

Rear Yard Coverage:

Must comply with coverage standards of underlying zoning district.

Materials / Design:

ADU must relate to the primary dwelling by use of similar exterior wall materials, window types, trims, roofing material and roof pitch.

Landscaping of ADU must meet the standards of the underlying zoning district.


Must be separate from existing primary dwelling.

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