Permit guides

ADU Permits in Walnut Creek: a Homeowner's Guide

Walnut Creek offers pre-reviewed ADU plans and a dedicated review track — but hillside lots and design-match rules deserve respect.

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

Who handles your permit

ADU permits in Walnut Creek run through the Community Development Department, with the Building Division processing ADU applications on a dedicated review track. The city participates in Contra Costa County's broader ADU streamlining push, and typical plan-check review runs 4–8 weeks within the state's 60-day window.

What you can build

Walnut Creek's key numbers:

1,200 sq ftMax for a detached ADU

16 ftHeight limit for most detached ADUs

4 ftMinimum rear and side setbacks

1 + 1One ADU plus one Junior ADU per single-family lot

PRADUCity pre-reviewed plan program

$5–8kTypical permit fees for a standard detached ADU

The city assigns each new ADU its own address: the main dwelling's street address plus the letter 'A'. No new parking is required for ADUs or JADUs, and converted garages don't trigger replacement parking.

Pre-reviewed plans — with a caveat

Walnut Creek developed Pre-Reviewed ADU Plans (PRADU) for detached new construction, drawn to the California Residential Code, for an expedited review. Important: the city has been updating the PRADU plans for the 2025 Building Code — confirm they're available again before planning around them.

PRADU plans cannot be revised and must be permitted exactly as designed (mirroring/flipping the floor plan is allowed). You still prepare the site plan from the city's template and secure outside agency approvals — Fire and Sanitary districts sign off separately.

Design rules are specific: siding, trim, roof form and pitch, roofing, and window features must match the main home. Unusual shapes are out unless the main home shares them.

Check PRADU availability first. If the plans are still offline for the code update, you're on the custom track — plan the timeline accordingly.

What goes into the submittal

A Walnut Creek submittal typically includes:

Architectural plans, structural calculations, and Title 24 energy compliance
Site plan (city template for PRADU track)
Outside agency approvals: Fire Protection District and Sanitary District
Building permit application with fees
Certificate of occupancy at the end of inspections

Where applications usually get stuck

PRADU downtime. The code update has taken the fast track offline — verify status early.
Hillside overlay zones. Sloped lots add review steps and time; Walnut Creek has plenty of them.
Design-match details. Roof pitch, siding, and window features all have to echo the main house.
Outside agencies. Fire and sanitary approvals run on their own clocks.

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