Los Altos ADU Standards: LiveLarge Home Guide

If you’re planning to build an ADU in Los Altos, LiveLarge Home can help you navigate the city’s key development standards and ensure a successful project. Here’s an overview of the essential regulations and processes for building an ADU in Los Altos.
ADU Types:
- Attached ADU:
Created by adding to or converting part of the primary dwelling.
Maximum Size: 1,200 sq. ft. (up to 50% of the existing or proposed primary dwelling’s floor area).
- Detached ADU:
A separate structure or a converted existing structure (e.g., garage).
Maximum Size: 1,200 sq. ft.
- Junior Accessory Dwelling Unit (JADU):
Created by converting existing space within a primary residence.
Maximum Size: 500 sq. ft.
General Information:
ADUs provide independent living spaces for a variety of uses, such as affordable housing, rental income, or downsizing. They contribute to Los Altos’ housing goals by increasing the overall housing stock.
Regulations:
- Detached ADU:
- Maximum Height: 18 feet
- Setbacks: Minimum 4 feet (front, side, and rear)
- Building Separation: 5 feet
- Attached ADU:
- Maximum Height: 16 feet or the height of the underlying zoning district, whichever is greater
- Setbacks: Same as the primary dwelling
- Building Separation: 5 feet
- JADU:
- Maximum Height: N/A
- Setbacks: N/A
- Building Separation: 5 feet
Setbacks:
- Attached ADUs: No setbacks required, except for fire safety regulations.
- Detached ADUs: Follow the same setbacks as the main residence—minimum of 3 feet from side/rear, 20 feet from the front, and 30 feet in A Zones. At least 5 feet from the primary dwelling is required.
Second-Story ADUs: Permitted only if they are conversions and meet landscape requirements; otherwise, they are not allowed.
Lot Coverage:
- Attached: No additional coverage since they must remain within the existing structure.
- Detached: Limited to the same coverage as the primary residence, capped at 30% of the usable rear yard.
Kitchen Requirements:
- Detached/Attached ADUs: Must include a sink, refrigerator, cooktop/oven, and sufficient counter space and cabinets.
- JADUs: Must include a counter-top cooking appliance or hot plate.
For more details, contact the Planning Division at (650) 947-2750 or via email at planning@losaltosca.gov.
Let LiveLarge Home be your guide through the ADU process in Los Altos. With expertise in design and construction, including pre-approved plans and prefab options, we ensure your ADU meets local standards and enhances your property. Reach out today to get started on your ADU project!
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