Permit guides

ADU Permits in San Jose: a Homeowner's Guide

The ADU Ally program, preapproved plans, same-day issuance, and the paperwork that delays everyone — in plain language.

Last updated October 2026. Rules change; always confirm current requirements with the city before you build.

Who handles your permit

ADU permits in San Jose run through the Development Services Permit Center, and the city staffs a dedicated ADU Ally — ADU.Ally@sanjoseca.gov, (408) 793-5302 — as the single point of contact for preapproved-plan submittals. Custom plans go through the standard multi-department review (Planning, Building, Fire, Public Works). If you're using a preapproved design, the Ally path is the one you want.

What you can build

1,200 sq ftMax for a detached ADU under state law

800 sq ftBuildable by-right in San Jose

4 ftMinimum side and rear setbacks

7 plansCity-reviewed preapproved designs (476–799 sq ft)

Same-dayPermit issuance possible at the review meeting

20 daysTypical first-round building review for custom plans

The preapproved fast lane

San Jose's preapproved ADU program lists city-reviewed standard plans from approved vendors (currently 7 plans, roughly 476–799 sq ft, with more under review). You tailor the plan to your property per the city's Bulletin 211, email the site-specific package to the ADU Ally, and get an intake meeting — where same-day permit issuance is possible if the site documents are complete and accurate.

Don't touch the design. Any change to a preapproved master plan disqualifies it from expedited review and drops you into the regular plan-check queue. Pick the plan as-is or go custom from the start.

What goes into the submittal

Forms 310 (Building Permit Application), 311 (Owner-Builder), and 312 (ADU Property Owner Declaration)
Form 302 — every ADU in San Jose gets its own separate address
A letter from your water company with fire hydrant flow data — request this on day one; it's a classic delay
Site-specific plans per Bulletin 211, plus the ADU inspection checklist in the plan set
Fees: building fees plus public works clearance, park, school, and applicable taxes

Where applications usually get stuck

The hydrant letter. The single most avoidable delay — the water company letter takes time, and review can't finish without it.
Exclusion zones. Preapproved plans can't be used in geohazard, landslide, flood, or Wildland-Urban Interface zones — check your lot first.
Mid-process code changes. If the building code updates while your ADU is in review, you update with it.
Altered preapproved plans. Even minor-looking tweaks can void the expedited track.

Not sure where to start? That's the part we do. We confirm your lot's eligibility, assemble the Ally submittal package, and manage review and corrections — one point of contact.

Tell us what you need help with.

Not sure where to start? That's what we're here for.

Send your project

Erik — (916) 540-8960 · Vall — (916) 956-8106
office@pcg-engineering.pro