San José ADU requirements: size, setbacks, fire access and what to check first

Quick answers

• How big can an ADU be?Known limit

  City standards: a detached ADU up to 1,000 sq ft on lots of 9,000 sq ft or less, 1,200 sq ft on larger lots. State standards: up to 800 sq ft. A junior ADU is limited to 500 sq ft under either.

• How close to the property line?Known limit

  Both sets list 4 ft at the sides and rear. The City set allows zero for the first story if building and fire code requirements are met.

• How tall?Known limit

  City standards: 18 ft for one story, 25 ft with a second story. State standards: 16 ft for a detached ADU, a little more near major transit. Attached ADUs can be 25 ft under either.

• Is parking required?Known limit

  No, under either set of standards.

• Does fire access work on my lot?Can't determine

  The farthest side of the ADU should be within 150 ft of the curb along a 4 ft clear path and within 600 ft of a hydrant, and hydrant flow comes from a water company letter. Public records can't settle the path or the flow.

• Which fees apply?Needs your input

  ADUs of 750 sq ft or less are exempt from school and parkland impact fees. The building permit fee depends on the ADU's size.

Figures from the City's ADU Universal Checklist (Bulletin #210, updated September 16, 2026) for single-family lots. Statuses follow the Property File key: Known limit is a published rule, Needs your input depends on what you build, Can't determine needs a site visit, survey or letter.

The figures on this page come from the City's ADU Universal Checklist (Bulletin #210, updated September 16, 2026), its single-family standards table, the Fire Department's ADU checklist and the City's ADU pages. They apply to a single-family property; duplex and multifamily lots use a different table. For what California law guarantees statewide, read ADUs 101: A Plain-Language Guide to Accessory Dwelling Units in California. Outside San José, see how to check ADU feasibility on any California lot.

1. Does the property qualify?

• Is it in San José? The City's checklist says to confirm this with the "Incorporated" field in the property's record on SJPermits.org. "No" means another jurisdiction handles the ADU.
• Is the main home permitted? ADUs are allowed where the site has a legally built main residence (single-family, duplex or multifamily) with approved permits. If the main home isn't permitted, the checklist says an ADU is not allowed.
• Is there an open code enforcement case? Any active complaint or violation must be resolved before the City accepts ADU plans.

2. City or State standards: the single-family rules side by side

San José gives you a choice. You can design the ADU to the City's development standards (Municipal Code § 20.80.175) or to the State standards (§ 20.80.176). The two cannot be mixed: you choose all City standards or all State standards. Building and fire codes apply under either. These are the figures in the City's single-family table (Bulletin #210, updated September 16, 2026):

Under both sets, the table lists no parking requirement and no maximum number of bedrooms or bathrooms (building and fire codes still apply). For a junior ADU, the owner must live in the main home only if the JADU shares sanitation facilities with it, and the City requires a recorded JADU deed restriction (Form 313). For a historic property, the City set applies simplified historic design standards (§ 20.80.175(E)); the State set adds none.

"Not listed" means the City's table gives no figure ("N/A") for that cell. It does not mean there is no limit: building and fire codes, and the rest of the Municipal Code, still apply. Confirm the current code sections with the City's Planning Division before relying on them for a design.

3. Which set fits your lot

The better choice depends on what you want to build and the shape of the lot. Reading the two tables together:

• One larger backyard ADU. Only the City set allows a new detached ADU above 800 sq ft. In exchange, the ADU must sit behind the main home or behind a 45-foot front setback, leave at least 6 ft to the main home, and keep rear-yard coverage at or under 40%.
• A narrow or shallow lot. Only the City set allows a zero side or rear setback, and only if building and fire requirements are met. The fire access rules below measure along a 4-foot clear path to all sides of the ADU, so a wall on the property line usually needs a different layout or a Fire Variance. Ask Fire permit staff before designing to it. On the State side, the front setback can give way if that is the only way to fit an 800 sq ft ADU.
• A garage conversion plus a new unit. The State set lists a conversion ADU, a new detached ADU and a junior ADU on the same lot (a new attached ADU is not allowed alongside a conversion). The City set lists one ADU and one junior ADU.
• A two-story detached ADU. The City set allows 25 ft with a second story. The State set's detached height is 16 ft (18 ft with a pitched roof near major transit), which rarely fits two stories.
• A historic property. The State set adds no historic design standards; the City set applies simplified ones.

None of this decides a specific lot. Easements, trees, the fire access path and the existing buildings can each rule out a footprint that the tables allow.

4. What designations apply to the lot?

The checklist lists six property designations that change how an ADU must be designed or what clearances it needs:

• Flood zone. In flood zones A, AE, AH or AO, plans must follow the flood design requirements in the City's ADU plan requirements (Bulletin #211). Zones D and X are not subject to them.
• Geohazard and seismic hazards. A geohazard or landslide designation requires a Geologic Hazard Clearance. A liquefaction designation requires a Geologic Clearance when two or more units are being built.
• Historic property. If the property is on the City's Historic Resources Inventory or the state's historical resources list and you use the City standards, simplified design standards apply.
• Wildland-urban interface. Properties in a wildland-urban interface zone must meet the City's WUI fire conformance requirements.
• Easements. Construction is often not allowed inside an easement area. The checklist points to the title report from your purchase as the reliable source.
• Nonbuildable area. If the ADU would sit where a swimming pool was demolished, the submittal needs pool demolition documents or a geotechnical report and foundation design.

A lot in a geohazard, landslide, flood or wildland-urban interface area cannot use the City's same-day preapproved plan path (see permit process).

5. Fire access and water

The Fire Department reviews ADU plans under the California Fire Code. Four questions depend on the lot's shape and on the street, and they rule out more designs than any size limit:

• Access path (150 ft). The City's checklist and FAQ ask whether every part of the ADU is within 150 ft of the street curb, measured along a clear path at least 4 ft wide. The Fire Department's own ADU checklist (updated October 6, 2025) states the same limit from the fire apparatus access road, measured along the approved route, and also requires 3 ft of clearance from projections such as eaves to the property line.
• Hydrant distance. The City's checklist and FAQ ask whether all exterior walls of the ADU are within 600 ft of a hydrant. The Fire Department's checklist measures from the hydrant to the start of the fire access route instead, and allows 600 ft if the building is fully sprinklered but 400 ft if it is not. If the lot is near either limit, ask Fire permit staff (408-535-7750) which measurement applies before you design.
• Water flow. At least 1,000 gallons per minute at 20 psi must be available from the closest hydrant. You get this as a letter from your water company and submit it with the permit application. The City says missing water-flow letters are a main reason permits are delayed, so request it early. If the flow is lower, Fire staff decide whether added safety measures are needed.
• Sprinklers. If the main home has fire sprinklers, the ADU must too. If an attached ADU is over 500 sq ft and the home and ADU together exceed 3,600 sq ft, the whole house and ADU must be sprinklered.

Distances are measured along the path, not in a straight line, so they can be longer than the lot's depth suggests. If a limit is missed, the project may need a Fire Variance with added safety measures, such as sprinklers. Both the main home's and the ADU's address numbers must also be visible from the street; the ADU gets a unit number, which you request with Form #302 and submit with your plans.

6. Permit process and timing

1. Complete the ADU Universal Checklist and choose the City or State standards.
2. Get early feedback if you need it. Basic questions to a City planner by phone (408-535-3555) or email (ZoningQuestions@sanjoseca.gov) are free and do not include plan review. A preliminary virtual meeting about a specific design is billed at the Planning Division's hourly rate, which the City's ADU Project Process page listed as $398 an hour with a 30-minute minimum on October 24, 2026.
3. Prepare plans to the City's ADU Building Plan Requirements (Bulletin #211), and request the water-flow letter.
4. Apply on SJPermits.org and upload plans to SJePlans. A Permit Specialist prescreens the package before plan review starts; incomplete plans are not processed.
5. Plan review. The City says the first round of building review typically takes 20 business days, and that accurate, complete plans should stay within one or two review cycles.
6. Pay the remaining fees, receive the permit and build, with inspections against the City's ADU inspection checklist (Bulletin #213).

Preapproved plans. The City lists ADU designs from outside vendors whose building plans it has already reviewed; the site-specific plan is still required. If that plan is accurate and complete, the City says the permit may be issued the same day as the plan review meeting. The lot must be zoned residential with an existing single-family home or duplex, and must not be in a geohazard, landslide, flood or wildland-urban interface area. Projects that need a deferred structural submittal, a clearance or a variance take longer.

7. Fees and costs

• Building permit. The fee depends on the ADU's size. The City publishes a Building Fee Estimator and fee schedule.
• School and parkland impact fees. ADUs of 750 sq ft or less are exempt; at 751 sq ft or more, school and parkland fees apply (Bulletin #210, September 16, 2026 edition, which matches state law, Gov. Code § 66311.5). The City's FAQ page still says "less than 750." Parkland fees vary by location, and the City says to ask your school district about its fees. The permit isn't issued until they're paid.
• Other processes, if needed. Geologic hazard review and clearance, a tree removal permit (a separate process applies to heritage trees) and fire variance fees.
• Property tax. The City's FAQ says property taxes increase based on the value of the ADU.

The City suggests two ways to lower costs: use a preapproved plan, and keep the ADU small enough to avoid impact fees.

8. Renting, selling and utilities

• Renting. You can rent the main home and the ADU to different tenants. The City's FAQ says the minimum rental term for an ADU is 30 days, including on Airbnb, and fair housing laws apply.
• Selling the ADU separately. The City says an ADU can only be sold on its own after a condominium conversion of the home and ADU, through its ADU condominium process.
• Utilities. The City's FAQ says PG&E now requires an ADU to have its own utility meter (confirm with PG&E); a junior ADU does not need one. The City has paused enforcement of its natural gas ban, so a detached ADU can use gas or be all-electric.

9. Look up your lot

• Incorporated status, flood zone, hazard designations and permit history: search the address or parcel number on SJPermits.org ("Property Information").
• Zoning district: the City's maps commonly used for planning, including the zoning map.
• Parcel number and lot details: the Santa Clara County Assessor's property search.
• Easements: the title report from your purchase.
• Water flow: your water company. The City's ADU FAQs list San Jose Water, Great Oaks Water and the San Jose Municipal Water System, with how to request the letter.

What public records can't establish

• Easements. Recorded maps may show easements, but the City's checklist says they can be less accurate than a title report.
• Water flow at the hydrant. This comes from a letter from your water company, not from a public map.
• Actual site conditions. Whether a 4-foot clear path really exists, what's built where, and which trees are on the lot need a site visit and a survey.
• Which fire measurement applies. The City's checklist and the Fire Department's checklist measure hydrant distance differently; Fire permit staff decide for a specific project.
• The City's decision. Plan review, not a records search, decides whether a specific design is approved.

How LedgeX helps

LedgeX is in private testing for San José single-family lots. A Property File applies the rules on this page to one parcel, and marks the questions above that public records can't settle.

What this page does not establish

• Whether an ADU fits on any specific property. This page sets out the rules and the questions; it does not answer them for a parcel.
• Rules for duplex, multifamily or tiny-home-on-wheels projects. The City uses different tables and checklists for those.
• The ordinance text itself. The figures come from the City's bulletin, dated September 16, 2026 and marked "subject to change," and from the City's ADU pages. This page does not quote the Municipal Code directly; check the current code before a design is final.
• Rules after the verification date. Last verified October 24, 2026. The City updates its bulletins and California amends ADU law most years. Where a City standard conflicts with state ADU law, state law controls. Two state laws signed in September 2026 take effect January 1, 2027: AB 956 requires cities to approve two new detached ADUs on a single-family lot, and SB 1117 limits impact fees on ADUs over 750 sq ft to the area above 750 sq ft. The City's tables above predate both.
• Fees. Building permit and impact fee amounts were not checked; use the City's fee estimator for a current figure.

Sources

• City of San José, ADU Universal Checklist (Bulletin #210, updated September 16, 2026), Parts 1 to 5 and the single-family standards table
• San José Fire Department, Accessory Dwelling Unit (ADU) Fire Plan Review Checklist (updated October 6, 2025), items 1 to 5
• City of San José, ADU FAQs: fees, review time, renting, selling, utilities, fire questions
• City of San José, ADU Project Process
• City of San José, Preapproved ADUs
• City of San José, Online Permits at SJPermits.org, property and permit records
• California HCD, Accessory Dwelling Unit Handbook, for state ADU law