Permit guides

ADU Permits in Petaluma: a Homeowner's Guide

What you can build, which permits you need, and how 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

Petaluma's Building Division, part of the Community Development Department, handles ADU permits. The building counter is in the West Wing at 11 English Street, Petaluma, CA 94952 — walk-ins run Monday through Thursday, 10am to 3pm, and the counter is closed on Fridays. New applications go through the city's Permits & Planning Hub online portal, and building staff can be reached at (707) 778-4301. Unincorporated Sonoma County parcels use Permit Sonoma instead — a separate agency with its own portal.

What you can build

Petaluma's own standards are a bit tighter than the state baseline — note the 1,000-square-foot detached cap:

1,000 sq ftMax for a detached ADU — Petaluma's own cap

50%Max for an attached ADU (share of existing home)

500 sq ftMax for a Junior ADU, carved from existing space

16 ftHeight limit (up to 21 ft if you keep a 5 ft rear setback)

4 ftSide and rear setbacks for detached and attached ADUs

15–20 daysBusiness days for a first residential plan check; a second check takes about 10

There is no minimum lot size for an ADU under state law. Conversions of existing space keep their current footprint — no new setbacks apply to the conversion itself.

Design help and plan resources

Petaluma doesn't publish its own shelf-ready plan library. Instead, the Building Division provides an ADU Checklist that spells out the application requirements, and the Napa Sonoma ADU Center offers regional resources — an ADU Calculator, an ADU Workbook, and free customized feasibility consults. Most owners here go the custom route, drawn by a design professional.

Pre-approved doesn't mean permit-free. You still need a building permit, and reviewers still verify site placement, foundation conditions, utility connections, and fire access for your specific property.

What goes into the submittal

Site plan — lot lines, existing structures, setbacks, easements, utility locations.
Architectural plans — floor plans, elevations, sections.
Structural details and calculations — foundation, framing, shear walls.
Title 24 energy compliance — required forms and documentation.
Electrical, plumbing, and mechanical layouts — and remember, new ADUs must be all-electric.
Stormwater drainage plan — directed to the public street or an approved storm drain, signed and sealed by a civil engineer.
Utility connection plans — water and sewer connections shown on the plans.

Where applications usually get stuck

All-electric. Petaluma requires new buildings to be all-electric — gas is out for new ADUs, so size the electrical panel and HVAC from day one.
Stormwater. Drainage from the new ADU must be directed to the public street or an approved storm drain, with plans signed and sealed by a civil engineer.
Historic areas. Parts of Petaluma fall under historic review (SPAR) — materials, windows, and lighting can all draw comments.
Right-of-way work. Any work in the public right of way needs a separate encroachment permit.
Friday counter. The city hall counter is closed on Fridays — plan visits and questions around it.

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.

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