Palo Alto ADU Permits & Building Guide
Building an Accessory Dwelling Unit (ADU) in Palo Alto is one of the most valuable investments a homeowner can make. At Apex Homes, we provide complete in-house ADU design and development services, helping Palo Altos families create additional living space, generate rental income, and increase property value. With streamlined processes and fee waivers for smaller units, ADU constructions in Palo Altos can be both cost-effective and efficient. Whether you are planning a backyard rental, a space for family members, or a flexible studio, Palo Alto provides excellent opportunities for ADU development
ADU Regulations in Palo Alto
Palo Alto allows ADUs on both single-family and multi-family lots, though requirements differ depending on lot type.
On single-family lots, homeowners may build one detached or attached ADU, as well as one Junior ADU. Detached and attached ADUs may be up to 900 square feet for one-bedroom layouts or up to 1,000 square feet for units with two or more bedrooms. JADUs may be up to 500 square feet. Detached ADUs must maintain at least three feet of separation from the main home, while attached ADUs must be set back at least four feet from the side and rear property lines. Height limits allow attached ADUs to reach up to 25 feet or the zone maximum, whichever is lower, while detached ADUs may reach 45 feet in RE zones and 30 feet in OS zones.
On multi-family lots, property owners may build up to two detached ADUs in addition to attached ADUs totaling up to 25 percent of existing units. Detached ADUs must be at least 150 square feet in size, with no maximum square footage limit, while JADUs may be up to 500 square feet. Setbacks must be at least four feet from the side and rear property lines, with front setbacks determined by zoning requirements. Detached ADUs on these lots may be built up to 16 feet in height, or up to 18 feet it located within a half mile of transit or if the main structure is multi-story. Detached ADUs must also maintain a minimum three-foot separation from the primary dwelling.
The Palo Alto ADU Permitting Process
The ADU permitting process in Palo Alto begins with a pre-application meeting with the City’s Planning Department. This step helps confirm zoning, setbacks, and design compatibility for the project.
Next, homeowners prepare the required documentation, including architectural plans, structural calculations, site layouts, and utility connections. The city requires submission of the New Single-Family Residence / Detached ADU Checklist to ensure compliance.
Applications are filed online through the Accela Citizen Access (ACA) portal. Once submitted, a project coordinator is assigned to confirm completeness. Plan reviews typically take between two and three months, depending on complexity. After approvals and fees are finalized, permits are issued electronically. Construction may then begin, followed by inspections and final approval.
Why Build An ADU in Palo Alto?
Palo Alto is one of Silicon Valley’s strongest housing markets, and ADUs provide significant advantages for homeowners. An ADU can increase property value by 25 to 35 percent while offering steady rental income in a community with consistently high demand.
ADUs also provide flexible living options, making them perfect for aging parents, adult children, or caretakers who need independence but want to remain close to family. With Palo Alto’s incentives, such as fee waivers for ADUs under 750 square feet and expedited review timelines, homeowners can take advantage of faster or more cost-efficient construction compared to traditional housing projects.