What Palo Alto lets you build in your backyard in 2026: sizes, setbacks, fees, the 60-day permit clock, and the local rules most guides skip.
The short answer
Yes, you can build an ADU in Palo Alto. A single-family lot can have one attached ADU, one detached ADU, and one junior ADU. A detached ADU up to 800 sq ft, 16 feet tall, with 4-foot side and rear setbacks must be approved, and no parking is required. Stay at 750 sq ft or less and impact fees drop to $0.
detached ADU the city must allow with 4-ft side and rear setbacks (PAMC 18.09.030)
impact fees for an ADU of 750 sq ft or less (Gov. Code § 66311.5)
for the city to approve or deny a complete application (Gov. Code § 66317)
ADU and JADU permits Palo Alto issued in 2024 (city year-end report)
Palo Alto doesn't just allow backyard homes. It counts them. City staff report ADU numbers to the City Council every quarter, and in 2024 the city issued 124 ADU and JADU permits.
A lot has changed since our 2020 Palo Alto guide. The 6-foot setbacks are gone, the old 900 sq ft cap became two paths, and state laws effective January 1, 2026, changed fees, deadlines, and junior ADUs. Here are the current rules from the city's code (Chapter 18.09, updated 2025), its 2025 ADU guidebook, and state law, plus local details most guides skip.
Can you build an ADU in Palo Alto?
Almost certainly, if you have a house. Palo Alto allows ADUs in every zoning district where single-family or multifamily homes are permitted, and a single-family lot can hold up to three extra units: an attached ADU, a detached ADU, and a junior ADU.
An accessory dwelling unit (ADU) is a second home on your lot with its own kitchen, bathroom, and place to sleep. Eligible zones include R-1 and its subdistricts, R-E, R-2, RMD, the RM districts, and OS. In a commercial or mixed-use district, check with the Planner on Duty first.
1 attached ADU + 1 detached ADU + 1 JADU
PAMC 18.09.030, Table 1Conversions up to 25% of existing units (at least one), plus up to 8 detached ADUs, but no more than the number of existing units
PAMC 18.09.030Ministerial: no hearing, no architectural review for single-family lots
PAMC 18.09.020; Gov. Code § 66317How big, how tall, and how close to the fence?
Palo Alto has two paths. The state-protected path allows a detached ADU up to 800 sq ft, 16 feet tall, with 4-foot side and rear setbacks. The city path allows up to 900 sq ft for one bedroom or 1,000 sq ft for two or more, with extra privacy rules.
| Rule | State-protected path (PAMC 18.09.030) | City path (PAMC 18.09.040) |
|---|---|---|
| Max size, detached | 800 sq ft | 900 sq ft (1 bed) / 1,000 sq ft (2+ beds) |
| Max size, attached | Within the allowed space of the house | 900 / 1,000 sq ft, and no more than 50% of the house |
| Side and rear setbacks | 4 ft | 4 ft, plus 3 ft from the main house |
| Height, detached | 16 ft; 18 ft within a half-mile walk of major transit, plus 2 ft to match the main roof pitch. Taller limits apply in the R-E and OS zones. | |
| Height, attached | 25 ft or the zone's limit, whichever is lower; two stories max | |
| Privacy and design rules | Don't apply | Apply (window sills, obscured glass, lighting, entry direction) |
| Floor area and lot coverage | Not counted | Up to 800 sq ft exempt per lot |
Source: Palo Alto Municipal Code Chapter 18.09, Tables 1 and 2 (Ord. 5656, 2025), checked October 8, 2026.
On the city path, the rules get specific: 5-foot sills or obscured glass on some windows facing neighbors, exterior lights no higher than 7 feet, and an entry that doesn't face the same lot line as your front door unless the ADU sits in the rear half of the lot.
Pro tip
Under Palo Alto's code, a detached ADU of 800 sq ft or less with 4-foot setbacks isn't subject to the city's FAR, lot coverage, or privacy standards. If your plan fits, you skip a whole layer of design rules.
Do you need parking for an ADU in Palo Alto?
No. Palo Alto's code requires no parking for a new ADU, and you don't have to replace a garage, carport, or driveway space you convert or tear down to build one.
One catch: if you build a new main house and new ADUs at the same time, the city asks for two uncovered spaces for the house.
What fees will you pay for an ADU in Palo Alto?
Most backyard ADUs pay building permit fees and, at 500 sq ft or more, a school fee. Impact fees start only above 750 sq ft, and that's where the bill jumps.
Building permit fees
The city's guidebook estimates $2,000 to $8,000, depending on type and size.
City of Palo Alto J/ADU Guidebook 2025, p. 15Development impact fees
Not charged on ADUs of 750 sq ft or less or on JADUs. Above that, the guidebook estimates $10,000 to $80,000, scaled to the size of your main house.
Gov. Code § 66311.5(c); city guidebook p. 15School fees (Palo Alto Unified)
$4.79 per sq ft of residential construction. ADUs under 500 sq ft are exempt. A 640 sq ft ADU would pay about $3,066.
PAUSD School Impact Fees page; Gov. Code § 66311.5(c)(3)Utility connections
An ADU isn't a "new residential use" for connection fees unless built with a new house. Any required separate connection must be priced proportionately.
Gov. Code § 66311.5(b), (e)We went through the city's 2024 year-end report: of 100 ADU applications filed that year, 15 were sized between 740 and 750 sq ft. Palo Alto homeowners clearly know where the fee line sits.
Watch out
Palo Alto runs its own utilities. The City of Palo Alto Utilities provides electricity, water, wastewater, and natural gas, so your hookups go through the city rather than PG&E. Ask about utility fees early; the city's guidebook sends you to the Utilities Department for them.
For the full price of a finished ADU, see our 2026 California ADU cost guide.
Do you have to live on the property, and can you Airbnb an ADU?
You don't have to live on the property to build or rent an ADU. But Palo Alto requires any ADU or JADU rental to be for 30 days or more, so nightly rentals are out.
California law bars cities from requiring owner-occupancy for an ADU (Gov. Code § 66315). You can rent both the house and the ADU, but the ADU can't be sold separately. Planning to rent? Our step-by-step guide to renting out your ADU covers leases and tenant rules, and the rental & ROI calculator runs the numbers.
What about a junior ADU (JADU)?
A JADU is a unit of up to 500 sq ft inside your house, often a converted bedroom or attached garage, with an efficiency kitchen. It can share a bathroom with the house. In Palo Alto, you must record a deed restriction before the permit is issued.
The deed restriction takes seven steps: you notarize the city's form, the city signs it, and you record it with the Santa Clara County Clerk-Recorder before your planner signs off.
What changed in 2026
Palo Alto's code (PAMC 18.09.050) still says the owner must live in the house or the JADU. State law now requires owner-occupancy only when the JADU shares a bathroom with the house (Gov. Code § 66333, as amended January 1, 2026). Ask the city how it applies the rule to your plan.
How long does an ADU permit take in Palo Alto?
By state law, the city has 15 business days to tell you if your application is complete and 60 days to approve or deny a complete one. In practice, Palo Alto's average from submittal to ready-to-issue was 193 days in 2024, because that count includes time waiting for applicants' corrections.
Under Government Code § 66317, "if the local agency has not approved or denied the completed application within 60 days, the application shall be deemed approved." The clock starts only when the application is complete. In the first half of 2025, the city's average was 188 days.
| Phase (city guidebook) | Typical time |
|---|---|
| Planning: check eligibility, budget, financing | 1–3 months |
| Design: plans and construction drawings | 2–6 months |
| Permitting: submit, plan check, corrections | 1–2 months |
| Bidding: choose a contractor | 1–3 months |
| Construction and final inspection | 6–12 months |
City of Palo Alto J/ADU Guidebook 2025, p. 17. City data: 2024 year-end and 2025 Q2 ADU reports.
The delay you control is the quality of your plans: each correction round adds to the wait. Palo Alto takes digital submittals only, through Accela Citizen Access.
How does a factory-built ADU fit Palo Alto's rules?
A factory-built ADU gets the same city permit as any ADU for its location, foundation, and utilities. The difference: the state oversees the factory build, and the city inspects the work on your lot.
Bay Modular is a California factory-built housing manufacturer (HCD #1585366). We build each unit in Lathrop; it's delivered in a day and installed in about a week. Palo Alto's guidebook lists "Modular/Prefab" among ADU professionals.
Palo Alto's online ADU Plans Gallery listed four pre-approved plans on October 8, 2026, one of them prefabricated. Even those need "customized site-specific permits to review details such as the ADU location, emergency access, and foundation design."
Every Bay Modular ADU model, from the 256 sq ft Small Studio to the 640 sq ft 2 Bedroom ADU, is under 750 sq ft, so impact fees don't apply; the 480 sq ft 1 Bedroom ADU also skips school fees. All-in prices run $124,900 to $271,900, including permits, foundation, crane, and hookups. See all models and pricing & financing.
What local quirks should you know before you start?
A few Palo Alto rules aren't in state law: tree protections, flood-zone height limits, and rules for noisy equipment.
- Big trees. On the city path, an ADU can't remove more than 25% of a protected tree's canopy or roots, or dig in its protection zone (10 times the trunk diameter). Protected trees include native oaks 11.5 inches or wider and most trees 15 inches or wider.
- Flood zones. ADUs in a flood zone don't get the height extensions given to the main house.
- Heat pumps and AC. Allowed anywhere except the front setback (and 10 feet from the street side on corner lots), and must meet the noise ordinance.
"The City considers ADUs as an affordable housing unit and has worked to streamline its permit processes to support more ADUs in Palo Alto."
— City of Palo Alto Planning & Development Services, ADU page (October 8, 2026)
Who do you contact at the City of Palo Alto?
Start with the Planner on Duty at Palo Alto's Development Center. You can book a virtual or in-person appointment, or email and call the planning team.
City of Palo Alto, Planning & Development Services
Development Center: 285 Hamilton Avenue, Palo Alto, CA 94301 (appointments and limited walk-in)
Email: Planner@PaloAlto.gov · Phone: (650) 617-3117
City ADU page
Utilities (CPAU) customer service: (650) 329-2161
Palo Alto Unified school fees: Facilities and Construction, (650) 329-3938
How to find out what fits on your Palo Alto lot
Your lot decides as much as the code: where setbacks land, where the trees are, and how a crane reaches the backyard. A free lot assessment answers that first.
Send your address
Tell us where you live and what you'd like.
We check your lot
We review satellite imagery, mark the buildable area and delivery access, and check Palo Alto's rules.
You get your options
See which model fits and what's included. Free, no obligation.
Want to see one first?
Tour our factory in Lathrop and see how the units are built.
Frequently asked questions
What are the ADU rules in Palo Alto?
A single-family lot can have an attached ADU, a detached ADU, and a JADU. A detached ADU up to 800 sq ft, 16 feet tall, with 4-foot side and rear setbacks must be approved; 900 to 1,000 sq ft units come with extra privacy rules. No parking is required.
Does Palo Alto charge impact fees on ADUs?
Not on ADUs of 750 sq ft or less, or on JADUs. Above that, the city estimates $10,000 to $80,000, scaled to your main house. Permit and school fees are separate.
Can I rent my Palo Alto ADU on Airbnb?
No. Palo Alto requires ADU and JADU rentals of 30 days or more. Long-term rentals are fine, and you don't have to live on the property.
How long does it take to get an ADU permit in Palo Alto?
State law gives the city 60 days to decide on a complete application. The city's 2024 average, submittal to ready-to-issue, was 193 days, including time applicants spent on corrections.
Can I build a prefab or modular ADU in Palo Alto?
Yes. It needs a city permit for its location, foundation, and utilities like any other ADU, while the state oversees the factory build.
Find out what fits on your Palo Alto lot
Send your address. We'll check your lot and Palo Alto's rules and show you what's included. Free, with no obligation.
About Bay Modular Team
Bay Modular is a California factory-built housing manufacturer (HCD #1585366). We design and build backyard ADUs in our factory in Lathrop, CA, and install them across California. More about us
Sources
- City of Palo Alto, Accessory Dwelling Units page, accessed October 8, 2026.
- Palo Alto Municipal Code Chapter 18.09 (Ord. 5656, 2025), accessed October 8, 2026.
- City of Palo Alto, J/ADU Guidebook 2025.
- City of Palo Alto, ADU 2024 Year End Report (Feb. 24, 2025) and 2025 Q2 ADU Report (Sept. 15, 2025).
- City of Palo Alto, ADU Plans Gallery, accessed October 8, 2026.
- California Government Code § 66311.5, § 66317, § 66333 (effective January 1, 2026), and § 66315.
- HCD, ADU Handbook, March 2026.
- Palo Alto Unified School District, School Impact Fees; City of Palo Alto Utilities, Utilities Rates. Accessed October 8, 2026.
- Bay Modular Pricing & Financing, October 2026.
This guide is general information, not legal, tax, or financial advice. Rules and fees change; confirm details with the City of Palo Alto's Planning & Development Services, the Santa Clara County Assessor, and a lender before you build.
