ADU Rules & Pre-Approved ADU Plans in San Jose

Pre-approved ADU plans in San Jose

The City of San José keeps a list of preapproved ADUs: standard plans that City staff have already reviewed for code compliance. Today it lists 14 detached plans from 9 vendors, from 476 to 991 square feet and from 1 to 3 bedrooms. The vendors are ADU companies, contractors, architects and designers, and they sell the plans; the City asks you to contact them for options, pricing and how they install. It also advises having the vendor or contractor pull the permit, which keeps the liability with the professional.

The payoff is speed. If your site-specific plan and documents are accurate and complete, the City says the permit may be issued the same day as the plan review meeting. To qualify, the lot must be zoned residential with an existing single-family home or duplex, and it must sit outside geohazard, landslide, flood and Wildland-Urban Interface zones. A deferred structural submittal, a clearance or a variance can take longer.

Every San Jose plan is listed, with its size, bedrooms, bathrooms and vendor, in A-du’s index of San Jose pre-approved ADU plans. Neighboring cities publish their own lists: Santa Clara and Cupertino. A plan is pre-approved only in the city that approved it. Free plans drawn by cities themselves, from Oakland, San Ramon and Los Altos, are on the Build Marketplace.

What a San Jose ADU permit costs

The building permit fee depends on the size of the ADU, and the City has a Building Fee Estimator for a general idea. Size matters twice: since January 1, 2020, school and parkland impact fees do not apply to an ADU under 750 square feet, so the City itself suggests staying under 750 square feet, or choosing a preapproved plan, to save money. Some lots also need geological hazard review, a tree removal permit or a fire variance, each with its own fee. For a custom design, the City says the first round of building review typically takes 20 business days.

Fire department checks that stop San Jose ADUs

The San José Fire Department reviews every ADU, and these questions from the City’s ADU FAQs decide whether a design needs a fire variance or extra safety measures:

• Can a firefighter reach every side of the ADU within 150 feet of the street curb, along a clear path at least 4 feet wide?
• Are all exterior walls within 600 feet of a fire hydrant?
• Does the nearest hydrant deliver 1,000 gallons per minute at 20 psi? You submit a letter from your water company with the permit application.
• Is the main house sprinklered? Then the ADU needs sprinklers too. An attached ADU over 500 square feet, where the house and ADU together exceed 3,600 square feet, means sprinklers for both.
• Are the address numbers of both the house and the ADU visible from the street?

Long, narrow lots and flag lots are where the 150-foot rule bites. A test fit on your lot shows early where a detached ADU can go.

Renting an ADU in San Jose

The City says you can rent the house and the ADU to different people, and California law no longer lets a city require the owner to live on the property for a standard ADU. Fair housing law applies: you cannot refuse housing vouchers, and the minimum rental term is 30 days, so nightly short-term rental is out. Every ADU gets its own address through the permit, PG&E now requires an ADU to have its own meter, and the County Assessor raises property taxes by the value the ADU adds.

Legalizing an unpermitted ADU in San Jose

San José runs the state’s AB 2533 ADU and JADU Legalization Program for units built or converted without a permit before January 1, 2020. You show evidence of the construction date, hire a professional for as-built plans, and email the application with a signed Substandard Housing Checklist (Form #214) to the ADU Ally. An inspector then checks the unit for safety, not for full building code compliance, and only the corrections the inspector lists are required. The City says the process typically takes 4 to 6 months from a complete application.

If you have a unit like this, you can ask a licensed architect to review it. The request form is written around Los Angeles but takes any California address. The review is performed by Chris Koss, AIA, an independent licensed architect, under a separate written agreement with you, not by A-du, and whether a unit qualifies is for the City to decide.

Building in San Jose? Compare the City’s preapproved plans, test a design on your lot, or ask for a legalization review.

This guide is general information, not legal advice. A-du is not affiliated with the City of San José. ADU, fire and rental rules change; confirm current requirements with the City’s ADU Ally at the Development Services Permit Center.