Building an ADU in Palo Alto

What you can build in Palo Alto

ADUs are allowed on any property where single-family or multifamily homes are a permitted use. If your lot already has a home, you are eligible. If not, the city's handbook says to check your zoning and talk to the Planner on Duty.

Palo Alto's code has two sets of rules:

• State standards (Section 18.09.030). These cover the ADUs state law says a city must approve: conversions of existing space, an ADU or JADU inside a new home, a new detached ADU of up to 800 sq ft with 4-foot side and rear setbacks, and multifamily ADUs. The city's floor area ratio (FAR), lot coverage and privacy rules don't apply to these units. The code says that where it conflicts with Gov. Code 66323, "the Government Code shall prevail."
• City standards (Section 18.09.040). These apply to every other ADU, such as a larger ADU or an attached addition. They allow more size but add design and privacy rules.

On a single-family lot you can have one attached ADU, one detached ADU and one junior ADU. On a multifamily lot you can convert non-living space into ADUs (at least one, up to 25% of the existing units) and add up to eight detached ADUs, but no more than the number of existing units. With a new multifamily building, you can add two detached ADUs. RVs, tiny homes on wheels and yurts don't count as ADUs in Palo Alto. [1][2][4]

Size, height and setbacks

State standards. A new detached ADU can be up to 800 sq ft with 4-foot side and rear setbacks and the zone's front setback. It can be 16 feet tall, or 18 feet if the lot is within a half mile walk of a major transit stop or high-quality transit corridor; in that case, two more feet are allowed for a roof that matches the main home's roof pitch. Converting existing space has no size cap and no setback, "if condition is sufficient for fire and safety." A converted accessory structure can grow by up to 150 sq ft for a way in and out. ADUs in a flood zone don't get any height extension given to the main home.

City standards. An ADU can be up to 900 sq ft, or 1,000 sq ft with two or more bedrooms. An attached ADU also can't be more than 50% of the size of the house. (HCD, the state housing agency, says a percentage cap can't hold an attached ADU below 850 sq ft, or 1,000 sq ft with more than one bedroom.) Up to 800 sq ft of ADU space, combined, is exempt from your lot's FAR, lot coverage and maximum house size. Side and rear setbacks are 4 feet, and a detached ADU must be at least 3 feet from the main home. A detached ADU can be 16 feet tall (18 feet near major transit, as above). Taller limits apply in the RE and OS zones; confirm with a planner. An attached ADU can be 25 feet or the zone's limit, whichever is lower, with no more than two stories.

Every ADU must be at least 150 sq ft. Lofts with 5 feet or more of headroom count toward the unit's floor area. [1][2][5]

Design and privacy rules (city standards only)

ADUs built under the city standards must meet extra rules that protect neighbors:

• Second-story doors and decks can't face a neighboring property line. Second-story decks and balconies need solid screens at least 5 feet 6 inches tall.
• Second-story and loft windows facing a side or rear neighbor (other than egress windows) need a 5-foot sill height or fully opaque glass.
• Where feasible, the ADU's entrance shouldn't face the same lot line as the main home's entrance, unless it is in the rear half of the lot.
• Exterior lights must be mounted no higher than 7 feet and pointed down.
• Air conditioners and other equipment can go anywhere on the lot outside the front setback (and a 10-foot street-side setback on corner lots), but must meet the city's noise ordinance.
• On a property listed in the California Register of Historical Resources, the ADU must follow the Secretary of the Interior's Standards.

The code also limits how much an ADU project can harm a protected tree. If a protected tree must be cut to build an ADU that state law guarantees, you replace it under the city's Tree Canopy Replacement Table. The code says tree-protection compliance "shall not delay or cause the denial of an ADU or JADU building permit." [2]

Parking

Palo Alto requires no parking for an ADU. You don't need replacement parking when you convert or tear down a garage, carport or parking space to build an ADU.

If you choose to add covered parking for the ADU, it can be up to 220 sq ft. It counts toward the lot's floor area but not the ADU's size. An attached garage can't have an inside door into the ADU. If you build a new house and ADU at the same time, the house doesn't need covered parking, but you must provide two uncovered spaces somewhere on the lot. [1][2][4]

Fees

The city's 2025 handbook gives these rough ranges and says to ask Building and Planning staff for an estimate for your project:

• Building permit fees: $2,000 to $8,000.
• School fees: $4.79 per sq ft. These don't apply to ADUs under 500 sq ft.
• Development impact fees: $10,000 to $80,000, in proportion to the size of the main home. These don't apply to JADUs or ADUs under 750 sq ft.
• Utility fees: set by the city's Utilities Department.

State law says an ADU with 750 sq ft or less of interior living space pays no impact fees, and a larger ADU pays fees in proportion to the main home. School districts may charge fees on ADUs larger than 500 sq ft. Your property taxes will go up based on the value the ADU adds, but the main home isn't reassessed. See our guides to ADU costs, financing and property tax. [4][5]

How long it takes

State law requires the city to tell you within 15 business days whether your application is complete. When a home already exists on the lot, the city must approve or deny a complete application within 60 days. If it denies it, it must send a full list of what's wrong and how to fix it. See our ADU permit process guide.

The city says choosing a pre-approved design from its ADU Plans Gallery "will significantly expedite the review process." Palo Alto says it permits more than 100 new ADUs a year. [3][5]

Garage conversions and junior ADUs

You can convert a garage, a bedroom, a basement or a detached accessory structure into an ADU without a size cap. A legal non-conforming structure can be rebuilt in place, as long as it doesn't get taller, bigger or closer to the lot lines (beyond the 150 sq ft allowed for entry). The city can't make you fix other non-conforming zoning conditions on your lot first. See our garage conversion guide.

A junior ADU must be inside or attached to the main home (an attached garage counts) and can be up to 500 sq ft. It needs an efficiency kitchen. It can share a bathroom and laundry with the house. If it has no bathroom of its own, it needs its own entrance plus an inside door to the house. Before the permit is issued, you record a deed restriction saying the JADU can't be sold separately from the house.

Palo Alto's code also offers a JADU incentive: if you build a JADU that meets the zone's rules for houses and the code's other conditions (such as entrance direction and window rules), the main home gets bonus floor area equal to the JADU's size. The total bonus and exempt area on the lot can't exceed 800 sq ft. [1][2][4][6]

Renting, selling and owner occupancy

Rentals of any ADU or JADU must be for 30 days or more. The city doesn't require you to live on the property to build an ADU.

An ADU can't be sold separately from the main home "except as allowed under Government Code Section 66341." HCD describes that as a narrow exception for properties built by a qualified nonprofit and sold to a qualified buyer.

For a junior ADU, Palo Alto's code says the owner must live in either the main home or the JADU, and the deed restriction includes that requirement. State law changed on January 1, 2026: HCD's handbook says owner occupancy is required only when the JADU shares a bathroom with the main home. If your JADU has its own bathroom, ask the Planner on Duty how the city applies this. [1][2][5][6]

Where Palo Alto and state law differ

In October 2024, HCD found that Palo Alto's 2023 ADU ordinance did not comply with state law in several ways. One finding was that the city allowed only "1 ADU and 1 JADU" on a single-family lot, when state law allows a conversion ADU, a new detached ADU and a JADU together. Others covered the 18-foot height near transit, the 150 sq ft entry expansion and the fire sprinkler rule.

The city amended Chapter 18.09 in 2025 (Ordinance 5656). The current code now allows one attached ADU, one detached ADU and one JADU, the 18-foot transit height, and the 150 sq ft expansion. It also says compliance with the city's tree-protection standards can't delay or deny a permit.

Two points still differ from state law as HCD describes it: the JADU owner-occupancy rule (see above) and the 50% cap on attached ADUs under the city standards, which HCD says can't hold an attached ADU below 850 sq ft (1,000 sq ft with more than one bedroom). State law generally overrides a stricter local rule, so if either affects your project, confirm with the Planner on Duty. See our California ADU law overview. [1][2][5][6][7]

Permit steps in Palo Alto

1. Check your lot and talk to a planner

   Read the city's ADU/JADU Handbook. Then book an appointment with the Planner on Duty through the city's ADU page, or email Planner@PaloAlto.gov to confirm your zoning and any flood zone or historic status. [3][4]

2. Pick state or city standards

   Decide whether your ADU fits the state standards (Section 18.09.030) or needs the city standards (Section 18.09.040), which allow more size but add privacy and design rules. [1][2]

3. Design the ADU or choose a pre-approved plan

   Hire a design professional, or browse the city's ADU Plans Gallery and contact a plan's designer. Gallery plans still need a site-specific permit. [3][4]

4. Apply online through Accela Citizen Access

   Create an account and submit your building permit application and plans on the city's Accela Citizen Access portal. The city says all permit submittals go through this portal and all payments must be made there. [8]

5. Record the JADU deed restriction (if building a JADU)

   Fill out and notarize the city's JADU deed restriction and submit it to the city. It must be recorded before the permit is issued. [3][6]

6. Respond to plan check and pay fees

   Pay permit fees, answer plan check comments and resubmit if needed, then pay any outstanding fees and receive your permit. [4]

7. Build and pass inspections

   Your contractor calls for city inspections during construction. You receive final approval when the work is complete. The city assigns the ADU a street address before the permit is finaled. [1][4]

Pre-approved and sample plans

• ADU Plans Gallery

  New city gallery of ADU designs pre-reviewed by staff for code compliance (the city is still adding designs); you contact the designer, and a site-specific permit is still required. [3]

Who to call

• Planner on Duty, Planning & Development Services

  ADU zoning questions and appointments (Planner@PaloAlto.gov)

  (650) 617-3117

  [3]

• Development Center (Building)

  Permit applications, plan check and inspections (building@paloalto.gov)

  (650) 329-2496

  285 Hamilton Avenue, Palo Alto, CA 94301

  [4][8]

Questions people ask