ADUs and garage conversions Palo Alto

Building an ADU in Palo Alto under the state's standards or the city's

Palo Alto lets an ADU follow either of two sets of standards. The state path allows an 800-square-foot detached unit, 16 feet tall and 4 feet from side and rear lines, on any eligible lot. The city path allows 900 square feet with one bedroom or 1,000 with two or more, in exchange for privacy rules on windows, decks and lighting. On an ADU-only project, staying under 800 square feet also lets a protected tree come out without the usual ordinance steps.

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  • Rules on this page checked against 8 public sources, October 2026
The Ramona Street Architectural District in downtown Palo Alto
The Ramona Street Architectural District in downtown Palo Alto. Photo: Sanfranman59, CC BY-SA 3.0, via Wikimedia Commons.

How ADU and garage conversion work goes in Palo Alto

Palo Alto rules that decide the ADU's shape

  1. Protected trees and the 800-square-foot line

    Urban Forestry's guidelines, updated in September 2026, sort ADUs by the zoning table they fall under. A state-pathway project in PAMC 18.09 Table 1, including one detached ADU up to 799 square feet, may remove trees, protected ones included, without meeting the tree ordinance's requirements, and needs no arborist report, though trees that stay may still need protection. A Table 2 ADU, essentially 800 square feet or more, can remove a protected tree only under PAMC 8.10.050, with the 14-day public posting and canopy replacement, unless no other layout meets the state minimum. Both paths need the Tree Disclosure Statement on the T1 Tree Protection Sheet.

    Source: City of Palo Alto, Guidelines for Trees & ADUs (paloalto.gov)

  2. CPAU's utility service application

    Electric, water, gas and wastewater service for an ADU come from the city's own utility, through a Utility Service Application with an ADU / Conversion box to tick. The form asks for a separate application, with load information, for each meter requested, and notes only one service per parcel. Its plan checklist adds that an ADU must have an address before service can be established, that elevations show the gas and electric meters in relation to windows, vents and other ignition sources, and that the site or plumbing plan shows the city sewer cleanout and the ADU's proposed sewer connection.

    Source: City of Palo Alto Utilities, Utility Service Application (paloalto.gov)

  3. Fee lines at 500 and 750 square feet

    Every unit pays building permit fees, but the city's guidebook says development impact fees do not apply to a JADU or to an ADU under 750 square feet, and above that line they are proportional to the size of the primary unit. School fees do not apply to a JADU or an ADU under 500 square feet. Utility fees come separately from the Utilities Department. The guidebook also notes that the main house is not reassessed, though property taxes rise with the value of the new unit.

    Source: City of Palo Alto, J/ADU Guidebook 2025 (paloalto.gov)

  4. The detached ADU permit set

    Palo Alto takes ADU applications only electronically, through Accela Citizen Access. Its checklist for detached ADUs under the 2025 California Building Standards Code asks for architectural, structural and mechanical, electrical and plumbing plans, Title 24 energy forms, structural calculations and equipment specifications, plus a CALGreen sheet at the Mandatory plus Tier 2 level, beyond the state's mandatory measures. The city is also filling an ADU Plans Gallery with designs its staff have pre-reviewed; those still need site-specific permits covering location, emergency access and the foundation.

    Source: City of Palo Alto, Master ADU Permit Checklist (paloalto.gov)

State license for this work: B General Building. Look up a contractor's license on the CSLB website (cslb.ca.gov).

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Free to request, and you agree the scope and price with the person you hire before work starts. In California, a job over $1,000 in labor and materials, or one that needs a building permit, must be done by a contractor licensed by the CSLB in the right class. Ask for the license number and check it at cslb.ca.gov.

The work

Four ways Palo Alto owners add a second home

  • An 800-square-foot cottage on the state path

    Any eligible Palo Alto lot can take a detached ADU of up to 800 square feet, 16 feet tall, 4 feet from the rear and side lot lines, with the zone's front setback. Within half a mile of a major transit stop or a high-quality transit corridor, and the city's map marks El Camino Real as one, the limit rises to 18 feet, plus 2 feet to line the roof pitch up with the main house. The city's tree guidelines treat a detached unit of up to 799 square feet as a state-pathway project.

  • A larger unit that trades size for privacy

    The city path allows a detached ADU of 900 square feet with one bedroom or 1,000 with two or more, at least 3 feet from the main house, and taller in two zones: 25 feet in RE and 30 feet in OS. In return come additional city standards. The entry faces a different property line than the main house unless the ADU sits in the rear half of the lot or on a corner lot, egress windows facing a neighbor use obscured glass, outdoor lights mount at 7 feet or lower and point down, and second-floor doors and decks may not face a neighboring property line.

  • Converting the garage of an Eichler

    Palo Alto's Eichler guidelines ask owners to explore a garage conversion or an attached ADU first, because a cottage in an Eichler back yard is highly visible from the main house and its neighbors. Converted garage or carport parking does not have to be replaced. An attached garage that stays may not have interior access to the new unit, and the guidelines prefer an ADU entrance that does not face the street, with clerestory windows above eye level rather than windows looking into the main yard.

  • A JADU with a recorded deed restriction

    A junior unit must sit inside the main house, up to 500 square feet, with an efficiency kitchen, and it may share a bathroom and laundry with the house and have an inside door to it. Palo Alto requires owner occupancy in either the house or the JADU. Before the city issues a permit, the owner fills in and notarizes a deed restriction, recorded against the property, saying the JADU cannot be sold apart from the house and limiting its size and attributes.

A two-story laneway house with a garage, a small detached home at the back of a lot in Vancouver
A two-story laneway house with a garage, a small detached home at the back of a lot in Vancouver. Photo: Mike, CC BY-SA 2.0, via Wikimedia Commons.

The houses here

Eichler tracts, older lots and where the units go

ADU applications in Palo Alto split almost evenly across Oregon Expressway: in 2024, 44 percent came from north of it and 56 percent from south. The city's 2018 Eichler guidelines place most of its roughly 2,700 Eichlers in the central and southern parts of town, post-and-beam houses on slabs with radiant heating pipes, and count single-story overlay districts on eleven Eichler tracts. For an ADU those guidelines are voluntary, but they steer a designer toward converting a garage or adding an attached unit before building a detached one, and toward flat or low-slope roofs and clerestory windows. One structural limit is not optional: a basement under the main house may not be extended beneath an ADU or JADU.

Before you hire

Questions for a Palo Alto ADU contractor

  • Is the design on the state path or the city path, and what do we give up in window, deck and lighting rules for the extra size?
  • Is the detached unit drawn under 800 square feet, and how does that change what can happen to the protected tree beside it?
  • Who prepares the CPAU utility service application and the meter elevations, and when will they go in?
  • Does the plan set meet CALGreen Tier 2 for a detached ADU, and does the license at cslb.ca.gov show B General Building?
  • For a JADU, who prepares the notarized deed restriction, and is it recorded before the permit is issued?

Timing

Start the CPAU application at the design stage

City of Palo Alto Utilities' Electric Engineering reviews a complete utility service application and works out what the service needs within 45 business days, and it returns incomplete applications unprocessed. Connection charges must be paid in full before any utility work is scheduled, and permanent services are installed 30 to 40 business days after that payment and after any work required of the applicant. Electric meters go in only with final inspection tags in place, so the electric application belongs early in the ADU schedule, not after framing.

Questions

What Palo Alto owners ask before building an ADU

Can I sell my Palo Alto ADU separately from the house?

Generally no. The city's guidebook says only ADUs developed by a qualified nonprofit corporation can be sold separately from the primary residence, and a JADU's recorded deed restriction says it cannot be sold apart from the house. Plan the unit as a rental or a home for family; any rental of an ADU or JADU must run 30 days or more.

Can I add an attached ADU when my Palo Alto house is already at its floor-area limit?

Yes. The guidebook lets an owner add 800 square feet to the home as an attached ADU above the maximum floor area ratio and lot coverage. Using the city's additional standards, the attached unit can reach 900 square feet with one bedroom or 1,000 with two or more, two stories, and 25 feet or the zone's limit, whichever is lower, with 4-foot rear and side setbacks.

Does a new ADU in Palo Alto need a parking space?

No parking is required for a new second unit, and covered parking converted to an ADU does not have to be replaced. The guidebook's one exception: when a new house is built together with a second unit and has no covered parking, replacement uncovered parking is required. Covered parking of up to 220 square feet can be added without counting toward the unit's size.

Where can the heat pump for a Palo Alto ADU go?

Under the city's additional standards, air conditioners, heat pumps and other noise-producing equipment may go anywhere on the site, but they must keep the zone's front setback, a 10-foot street-side setback on a corner lot, and meet the city's noise ordinance, PAMC Chapter 9.10, at the nearest property line. Settle the location before the electrical and utility plans are drawn.

How many units can a Palo Alto single-family lot hold?

Two ADUs and one JADU, according to the city's guidebook. A multifamily lot can convert non-livable space for at least one ADU or up to 25 percent of the existing units, and add up to eight detached ADUs, never more than the number of existing units. For more units on a single-family lot, the city points owners to Senate Bill 9.

Where these facts come from

Checked against these public sources in October 2026. Rules and programs change: confirm permit requirements with the city before work starts, and a contractor's license on the CSLB website.

  • paloalto.gov: Accessory Dwelling Units (paloalto.gov)
  • paloalto.gov: adu jadu handbook 2025 (paloalto.gov)
  • paloalto.gov: trees and adus guidelines (paloalto.gov)
  • paloalto.gov: single family residential project application packet 2026 (paloalto.gov)
  • paloalto.gov: master permit checklist for detached adus (paloalto.gov)
  • paloalto.gov: 2024 annual adu report (paloalto.gov)
  • paloalto.gov: 2018 04 02 palo alto eichler design guidelines adopted design guidelin (paloalto.gov)
  • cslb.ca.gov: Licensing Classifications Detail (cslb.ca.gov)

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