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Building an ADU in Palo Alto, CA

Checked against the city's ADU pages on Oct 18, 2026.

Can I build one?
Yes, up to 1,000 sq ft A detached ADU of 800 sq ft or less with 4 ft setbacks skips most local rules. Larger ones can be 900 sq ft, or 1,000 sq ft with 2+ bedrooms. No parking required.[1][2]
What will the city charge?
$7,346 Detached ADU building permit (flat fee). School and utility fees extra. See every fee[3]
Who builds here?
13 licensed builders Each lists Palo Alto on its own site and holds an active CSLB license. See the list
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Licensed ADU builders in Palo Alto

Ranked by a public score anyone can check: license, years licensed, ADU types and cities shown on their own sites, a local office, and published prices. Nobody pays to move up. Quote requests go to our team with the builder you picked. How we rank

What Palo Alto allows

  • Detached ADU, max size[1][2]

    800 sq ft or less under the state-exempt rules. Larger: 900 sq ft, or 1,000 sq ft with 2+ bedrooms

  • Attached ADU, max size[2]

    900 sq ft (1,000 sq ft with 2+ bedrooms), and no more than 50% of the house

  • Junior ADU (inside the house)[1]

    Up to 500 sq ft

  • Height[1][2]

    Detached: 16 ft, or 18 ft within 1/2 mile of major transit (+2 ft for roof pitch). Attached: 25 ft or the zone limit, whichever is lower, two stories max

  • Side and rear setbacks[2]

    4 ft side and rear; 3 ft from the main home

  • Floor area and lot coverage[2]

    Up to 800 sq ft of ADU space is exempt from FAR, lot coverage and max house size

  • Units on a single-family lot[1]

    1 attached ADU + 1 detached ADU + 1 JADU

  • Parking[1][2]

    None. No replacement parking when you convert or remove a garage or parking space

  • Owner must live on site[2][4]

    No for an ADU. City code requires it for a JADU; since 2026 state law requires it only when the JADU shares a bathroom
  • Minimum size is 150 sq ft. Rentals must be 30 days or longer.[1][2]
  • Fire sprinklers are not required in the ADU if the main home doesn't need them.[2]
  • Building the ADU can't damage a protected tree beyond set limits. If it has to, you replace the canopy under the city's tree manual.[2]
  • HCD flagged parts of the 2023 ordinance in October 2024. The city updated the chapter in 2025 (Ord. 5656).[5][2]
ADU rules in Palo Alto drawn on a typical lot Detached ADU, city standards: up to 1,000 square feet, 4 feet from side and rear lot lines, 16 feet tall. Parking: None required. Rear lot line Street Main house ADU up to 1,000 sq ft 16 ft tall 4 ft 4 ft 3 ft apart Parking: none required
Detached ADU, city standards. Not to scale.

City fees for an ADU in Palo Alto

Fee lines for an ADU in Palo Alto
Detached ADU building permit $7,346 per permit; $2,653 for a master-plan permit[3] Site-specific permits tied to a master plan: $3,929 for prefab, $5,481 for site-built.
Plan checks Building plan check 125% of the permit fee; planning and public works plan checks 35% each[3] The schedule does not say whether these apply on top of the flat ADU fee.
City guidebook ranges $2,000 to $8,000 in building permit fees; $10,000 to $80,000 in impact fees[6] Impact fees apply only at 750 sq ft and up.
Development impact fees (parks, community center, library, public safety, general government) $0 under 750 sq ft. At 750 sq ft and up, a share of the single-family rates: parks $18.75, community center $1.44, libraries $0.86 per sq ft; public safety $1,383 and general government $1,743 per unit[7][3] The share is in proportion to the size of the main home. JADUs and garage conversions with no added floor area are exempt.
School fees Palo Alto Unified $4.79 per sq ft; Los Altos SD $3.58 per sq ft[8][9][10][6] Only for ADUs over 500 sq ft. You pay the district directly; the city does not collect it.
Water capacity charge (City of Palo Alto Utilities) $3,750 for a 5/8 x 3/4-inch meter; $6,250 for a 1-inch meter[3][2] Charged when CPAU requires a new service. A JADU is not a separate unit for water, sewer or power.
Wastewater capacity charge (City of Palo Alto Utilities) $5,250 for a 4-inch connection with a 5/8-inch meter; $10,500 with a 1-inch meter[3]
School fee rates for districts in Palo Alto (2)

The city names two districts: Palo Alto Unified and, for some parcels, Los Altos School District.[8]

  • Palo Alto Unified School District[9][6]City guidebook: no school fee for JADUs or ADUs of 500 sq ft or less. $4.79/sq ft
  • Los Altos School District[10][11] $3.58/sq ft
Total cost in Palo Alto, fees plus building

How the permit works

  1. 1

    Meet the Planner on Duty

    Book a virtual or in-person appointment at the Development Center, 285 Hamilton Ave, to confirm your lot qualifies.[6]

  2. 2

    Design the ADU

    Hire a designer or pick a master plan from the city's ADU Plans Gallery. The guidebook plans 2 to 6 months for design.[6][12]

  3. 3

    Apply online

    Set up an Accela Citizen Access account and submit the application and plans for a completeness check.[12][6]

  4. 4

    Plan check and permit

    Pay permit fees, answer plan check comments, pay any fees still due, then get the permit.[6]

  5. 5

    Build and pass inspections

    Your contractor calls for city inspections. Final inspection approval closes the permit.[6]

Review time: The city's guidebook plans 1 to 2 months for permitting.[6]

State deadline: State law gives the city 15 business days to say if your application is complete and 60 days to approve or deny a complete one.[4]

Preapproved plans

Palo Alto's ADU Plans Gallery lists master detached designs. A site-specific permit tied to a master plan costs $3,929 for prefab or $5,481 for site-built, compared with $7,346 for a custom detached ADU.[12][3]

  • Palo Alto ADU Plans Gallery Designs listed on the city's ADU Accelerator site

We could not read the designer list on the gallery site. You buy plans from the designer.

Common questions

How big can an ADU be in Palo Alto?

A detached ADU can be 900 sq ft, or 1,000 sq ft with 2 or more bedrooms. At 800 sq ft or less with 4 ft setbacks, it follows the simpler state-exempt rules. A junior ADU inside the house is up to 500 sq ft.[1][2]

Do I need parking for an ADU in Palo Alto?

No. Palo Alto requires no parking for an ADU, and you don't have to replace a garage you convert or tear down.[1][2]

How much is an ADU permit in Palo Alto?

The flat building permit for a detached ADU is $7,346, or $3,929 to $5,481 with a master plan. Impact fees start at 750 sq ft, and Palo Alto Unified charges $4.79 per sq ft in school fees over 500 sq ft.[3][7][9]

How tall can an ADU be in Palo Alto?

16 ft for a detached ADU, or 18 ft within 1/2 mile of a major transit stop, plus 2 ft to match the main roof pitch. An attached ADU can be 25 ft or the zone limit, whichever is lower.[2]

Do I have to live on the property?

Not for an ADU. A junior ADU needs an owner living in the house or the JADU.[2][4]

Nearby cities

What we couldn't confirm

  • Palo Alto Unified's school fee page still shows the July 9, 2022 rate of $4.79 per sq ft; no newer rate found.
  • The fee schedule does not say whether plan check percentages are added on top of the flat ADU permit fee.
  • ADU Plans Gallery designer list could not be read.
  • The high school district for Los Altos SD parcels in Palo Alto is not confirmed.

Sources

Every fact on this page links to one of these. We read each one on the date shown.

  1. 1. City of Palo Alto (American Legal Publishing, official code host) PAMC 18.09.010-18.09.030 (Supp Checked Oct 18, 2026
  2. 2. City of Palo Alto (American Legal Publishing, official code host) PAMC 18.09.040-18.09.050: Table 2 local-standard units: 900 sq ft (1,000 sq ft with 2+ bedrooms), attached max Checked Oct 18, 2026
  3. 3. City of Palo Alto ADU flat permit fees, sf-based building fees, plan check %, impact fees, CPAU capacity charges Checked Oct 18, 2026
  4. 4. California Department of Housing and Community Development (HCD) All state ADU/JADU rules used in state_baseline.md (sizes, heights, setbacks, parking, owner-occupancy, JADU, Checked Oct 18, 2026
  5. 5. California HCD Ord Checked Oct 18, 2026
  6. 6. City of Palo Alto Cost & fee ranges, school $4.79/SF, timeline phases, parking Checked Oct 18, 2026
  7. 7. City of Palo Alto SF impact fee rates Checked Oct 18, 2026
  8. 8. City of Palo Alto PAUSD and LASD Checked Oct 18, 2026
  9. 9. Palo Alto Unified School District $4.79/sf residential as of July 9, 2022 Checked Oct 18, 2026
  10. 10. Los Altos School District $3.58/sf residential Checked Oct 18, 2026
  11. 11. Los Altos School District Adopted Dec 15, 2025 Checked Oct 18, 2026
  12. 12. City of Palo Alto ADU Plans Gallery, ACA portal, handbook and code links Checked Oct 18, 2026