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Permit guides
ADU Permits in Gilroy: a Homeowner's Guide
What you can build, which permits you need, and how the review actually works — in plain language.
Last updated October 2026. Rules change; always confirm current requirements with the city before you build.
Who handles your permit
The City of Gilroy Development Service Center — Building Division handles ADU permits at 7351 Rosanna Street, Gilroy CA 95020 (408-846-0451). Applications, payments, and inspection scheduling all run through the GO Permit online portal.
What you can build
California state law sets the baseline, and Gilroy's published standards add local detail — including height steps tied to the lot's context:
1,200 sq ftMax for a detached ADU
50% / 1,200Max for an attached ADU (50% of the main home, up to 1,200 sq ft)
500 sq ftMax for a Junior ADU, carved from existing space
16 ftHeight for most detached ADUs (18 ft near major transit or on multifamily lots)
4 ftMinimum rear and side setbacks for detached ADUs
1 + 1One ADU plus one JADU allowed per single-family lot
No additional parking is required, and replacement parking is not required when you convert covered parking. Fire sprinklers are only required if they're required for the primary structure. Converted structures keep their existing footprint and setbacks.
No pre-approved library — but unusually good paperwork
Gilroy doesn't publish a pre-approved ADU plan library, so plan on a full plan set and a full review. What it does publish is genuinely useful: a step-by-step ADU Pathway to Completion handout (revised August 2025), a detailed plan review checklist, and submittal guidelines — read all three before you draw anything.
What goes into the submittal
- Apply through the GO Permit portal with digital PDF plans — minimum 18"x24", maximum 36"x48", scale shown on every page. Gilroy is blunt: incomplete applications are not accepted or reviewed at all.
- Record a deed restriction with the submittal: the ADU can't be sold separately from the primary structure, and rentals under 30 days are prohibited.
- File the habitat paperwork. A Nitrogen Deposition Only (NDO) application and fee for the Santa Clara Valley Habitat Agency is required with the submittal — easy to forget, and a guaranteed correction if you do.
- Make the design compatible. The ADU must be compatible with the primary dwelling — similar architectural details, materials, and colors; worth resolving with staff early.
- Fees. Impact fees apply only to ADUs of 750 sq ft or more, in proportion to the primary unit's square footage.
Where applications usually get stuck
- Missing deed restriction or habitat NDO. Both are required at submittal — Gilroy won't begin review without them.
- Design compatibility comments. Materials, colors, and details that don't match the main house come back as corrections.
- Incomplete packages rejected outright. Gather everything first — and don't forget utility meter locations, sewer cleanouts, easements, and the flood-zone statement on the site plan.
Not sure where to start? That's the part we do. We look at your property, map the requirements, coordinate the plans and specialists, and manage the submittal and corrections — one point of contact.