Palo Alto / ADU construction
ADU Construction in Palo Alto
Palo Alto issued 124 ADU permits in 2024. The average approval took 193 days.
Palo Alto lets single-family lots add two ADUs and a junior ADU, with city standards that allow larger units than state law. We design and build ADUs here with the size path, the CPAU utility application and the city's review times planned from the first site visit.
PALO ALTO AT A GLANCE
How Palo Alto handles ADUs.
Palo Alto reviews ADUs through its Development Center, connects them through its own utility, and publishes ADU permit data every year. The numbers show where the time goes.
- 124
- ADU and JADU permits issued in 2024
- 193
- average days from application to approved permit, 2024
- 558
- square feet, the average ADU applied for in 2024
Planning
Development Center, Planner on Duty
Questions on eligibility, standards and special districts go to the Planner on Duty at 285 Hamilton Avenue, by appointment or email at Planner@PaloAlto.gov. Applications and plans are submitted electronically through Accela Citizen Access.
(650) 617-3117Palo Alto ADU page ↗Utilities
CPAU, not PG&E
A utility service application goes into the building submittal packet. After plans are approved, CPAU Electrical Engineering sets the connection charge, and underground service needs a CPAU trench and conduit inspection with 3 to 5 business days' notice.
(650) 566-4500New utility connections ↗Data
Where the time goes
The city's 2024 report counts 136 new ADU applications, 124 permits issued and 105 finals. Average construction from permit to final ran 519 days, including waits for owners to call inspections.
2024 ADU year-end report ↗STATE OR CITY STANDARDS
800 square feet by right. Up to 1,000 with conditions.
Under state standards any eligible Palo Alto lot can get an 800 square foot detached ADU, 16 feet high, or 18 feet within half a mile of major transit. Palo Alto's own standards allow 900 square feet with one bedroom and 1,000 with two or more, but add required city rules on windows, entries, decks and equipment placement. The city guidebook marks every rule as state or city.
Detached ADU
800 sq ft and 16 ft under state rules, 4 foot side and rear setbacks, at least 3 feet from the main home. City standards allow 900 or 1,000 sq ft.
Attached ADU
Up to 800 sq ft beyond the lot's maximum floor area and coverage, or 900 to 1,000 sq ft under city standards, up to 25 feet and two stories, with its own entrance.
Garage conversion
An existing garage or accessory structure converts at its existing height, and converted garage or carport parking does not have to be replaced.
Junior ADU
Up to 500 sq ft within the main home, with an efficiency kitchen. Owner occupancy and a recorded deed restriction are required.
Two ADUs plus a JADU
Single-family lots can build two ADUs and one JADU. Multifamily lots can add at least one ADU or up to 25 percent of existing units, plus up to 8 detached ADUs.
Efficiency kitchen
Every ADU and JADU needs at least a one-burner range, an oven or convection microwave, a 10 cubic foot refrigerator, a sink and a 24 by 36 inch counter.
PALO ALTO J/ADU GUIDEBOOK
State standards or city standards.
Palo Alto's 2025 guidebook separates the state baseline every city must allow from the city's more generous standards, which come with additional required design rules.
| State standards | City standards | |
|---|---|---|
| Detached ADU size | 800 sq ft | 900 sq ft with 1 bedroom, 1,000 sq ft with 2 or more |
| Attached ADU size | 800 sq ft | 900 or 1,000 sq ft, same bedroom rule |
| Detached height | 16 ft, 18 ft within 1/2 mile of transit | 25 ft in the RE zone, 30 ft in the OS zone |
| Side and rear setbacks | 4 ft | 4 ft |
| Extra design rules | None beyond state law | Window sill heights, entry orientation, deck screening, equipment placement |
| Parking | Not required | Not required |
Planning the work
How a Palo Alto ADU gets built.
Site check
Free visit. Zoning, transit distance for height, flood and historic status, and utility routes.
Standards and design
State or city standards chosen, then architectural, structural, Title 24 and CALGreen sheets drawn.
Permit and CPAU
Accela submittal with the CPAU utility service application in the building packet; plan check comments answered in full.
Build and final
CPAU trench and conduit inspection for underground service, building inspections, final and meters set.
MASTER ADU PERMIT CHECKLIST
What Palo Alto asks for with a detached ADU.
Palo Alto's submittal checklist for detached ADUs is built on the 2025 California Building Standards Code. A complete first submittal is the best defense against months of resubmittals.
In the plan set
- Floor, roof, elevation and section drawings
- Structural plans and calculations
- Electrical, mechanical and plumbing plans
- Title 24 energy compliance forms
- CALGreen Mandatory Plus Tier 2 sheet GB-1
Also plan for
- CPAU utility service application in the building packet
- Green building special inspection form
- Structural special inspection agreement before issuance
- Recorded JADU deed restriction, if a JADU is included
Expect a longer path when
- The lot is in a flood zone
- The home is in a historic district or listed as a historic resource
- The ADU is 750 sq ft or more and owes impact fees
- New underground electric service is needed
WHAT SLOWS ADUS IN PALO ALTO
Problems Palo Alto owners run into, and how we plan around them.
From the city's own ADU reports, its 2022 permit process review, state review letters and local coverage.
Approval takes more than six months on average.
Drawings, structural calculations, energy and CALGreen forms go in complete, since the city's 193-day average includes time owners spend on resubmittals.
Applications sit at pending resubmittal.
The city's quarterly reports show many ADU applications waiting on the applicant, so plan check comments are answered in one full round.
Construction stretches well past a year from permit to final.
Inspections are requested as soon as each stage is ready, since the 519-day average includes time waiting for owners to schedule them.
Sewer and electrical connections slow the project down.
The CPAU utility application goes in with the building packet, and sewer and electric routes are walked at the site visit.
Rules shift as the state pushes back on the city.
State housing regulators ordered Palo Alto to revise its ADU ordinance in 2022, so each design is checked against the current guidebook and state law, not older summaries.
Waiting about two weeks for an inspection.
Inspections are booked ahead in the schedule, as the city's 2022 review found that lead time was typically about two weeks.
Sources: City of Palo Alto ADU year-end report 2024 and quarterly ADU reports; Building Permitting Process Review, April 2022; HCD review letter, December 2022; Palo Alto Weekly ADU coverage, 2020 and 2022.
How big can an ADU be in Palo Alto?
800 square feet for a detached ADU under state standards, and up to 900 square feet with one bedroom or 1,000 square feet with two or more under Palo Alto's city standards. A junior ADU is limited to 500 square feet within the main home. City-standard units must also meet additional rules on window sill heights, entry orientation, decks and equipment placement.
How many ADUs can I build in Palo Alto?
Two ADUs plus one junior ADU on a lot with a single-family home, per Palo Alto's 2025 ADU guidebook. Multifamily lots can add at least one ADU or up to 25 percent of the existing units, plus up to 8 detached ADUs, as long as the detached count does not exceed the number of existing units.
How long does an ADU permit take in Palo Alto?
193 days on average in 2024, from application to a permit ready to issue, according to the city's 2024 ADU year-end report. That average includes time applicants spent preparing resubmittals. Average construction from permit to final inspection was 519 days, including time waiting for owners to schedule inspections.
Are there impact fees for an ADU in Palo Alto?
No, not for an ADU under 750 square feet or a junior ADU. Larger ADUs pay development impact fees proportional to the size of the main home, and school fees of $4.79 per square foot apply to ADUs of 500 square feet or more, per the city's 2025 guidebook. Utility connection charges are set separately by CPAU.
How tall can an ADU be in Palo Alto?
16 feet for a detached ADU under state standards, or 18 feet within half a mile of a major transit stop or the El Camino Real corridor, with 2 more feet allowed to match the main home's roof pitch. Attached ADUs can reach 25 feet and two stories, or the zone limit if lower.
Can I sell an ADU separately in Palo Alto?
No, in most cases. Palo Alto's guidebook says only ADUs developed by a qualified nonprofit corporation can be sold separately from the main home, and a junior ADU's recorded deed restriction bars a separate sale. Any ADU or JADU rental must be for 30 days or more.
