On single-family residential lots in Palo Alto, you can build one ADU (attached or detached) and one Junior ADU (JADU). ADUs are allowed on any property where single-family or multi-family residential is a permitted use.

Multifamily properties can build up to two detached ADUs and convert non-livable space into additional ADUs (up to 25% of existing units). The same 4-foot setback requirements apply to detached ADUs on multifamily lots.

Yes, Palo Alto allows Junior ADUs up to 500 square feet. A JADU must be located entirely within the existing single-family residence and requires an efficiency kitchen. JADUs may share a bathroom with the main home. A deed restriction is required before permit issuance, and owner-occupancy is required.

Palo Alto does not have a separate guest quarters classification. Any secondary living space with kitchen facilities would be classified as an ADU.

Detached ADUs in Palo Alto are limited to 1,000 square feet. ADUs up to 800 square feet with 4-foot setbacks and 16-foot height limits qualify for streamlined ministerial approval and cannot be denied due to lot coverage, FAR, or open space requirements.

Attached ADUs can be up to 800 square feet or 50% of the primary dwelling's floor area (whichever is greater), not exceeding 1,000 square feet. An extra 800 square feet can be added above maximum FAR and lot coverage limits for attached ADUs.

Yes. Under California state law, ADUs up to 800 square feet are exempt from lot coverage, FAR, and open space requirements. Basement space in the R-1 zoning district does not count toward floor area calculations if the finished floor is no more than 3 feet above grade.

Detached ADUs have a maximum height of 16 feet in most zones. Near transit, heights up to 17-18 feet may be allowed. Attached ADUs can reach the height of the primary dwelling if they comply with underlying zoning setbacks and daylight plane requirements. ADUs in R-E zones can reach 30 feet; OS zones allow up to 25 feet.

Attached ADUs in R-E and OS zones may have two stories. All other zones limit attached ADUs to single-story. All detached ADUs must be single-story dwellings. ADUs built in flood zones are not entitled to height extensions.

Detached ADUs require minimum 4-foot setbacks from the side and rear lot lines, plus at least 6 feet from any existing structures. Attached ADUs may require 6-foot setbacks from side and rear lot lines depending on configuration. Roof eaves may encroach up to 2 feet into setbacks, but windows, doors, and below-ground structures may not.

Detached ADUs must maintain at least 3 feet from the exterior walls of the primary dwelling, with 6 feet recommended for optimal access and maintenance.

Palo Alto processes qualifying ADU permits ministerially within 60 days. Overall, expect 2-4 months from application to permit issuance depending on project complexity. Before obtaining a permit, you must receive a street address assignment from the Planning Department. JADUs require a deed restriction to be recorded with the County prior to permitting.

Building an ADU in Palo Alto can cost $10,000-$25,000 or more in permit fees depending on size and complexity. ADUs under 750 square feet qualify for reduced or waived impact fees. Tree protection reviews may extend the approval timeline if your ADU is near protected trees.

Palo Alto does not routinely require soils reports for standard ADU projects. A site survey may be required depending on project location and proximity to property lines. Consult with the Planning Division early in your design process.

Generally, no additional off-street parking is required for ADUs in Palo Alto, especially for properties within half a mile of public transit. If parking is required, it cannot exceed one space per ADU. Parking requirements can be waived if the property is in a historic district.

Replacement parking is not required when a parking space is converted to an ADU or demolished to build an ADU. However, replacement parking is required if an attached garage is converted to a JADU.

If parking is required, it can be an uncovered space anywhere on the lot within the front or street-side yard setback. Tandem parking in driveways is allowed.