Walnut · ADU permits
ADU permits in Walnut
How to build a ADU in Walnut: permit pathway through Walnut Community Development Department, drawings required, local watch-outs, and a free address-level wizard for your Walnut lot.
Walnut context
Walnut's ADU ordinance is in Walnut Municipal Code Title 22. The city aligns with the California state baseline plus Hillside Standards for hillside parcels. Plan check is typically 60 days.
- Permit agency
- Walnut Community Development Department
- Median lot size
- 8,400 sqft
- ADU permits issued (2025)
- 151Source: Cal HCD Annual Progress Report 2025 (Table A2, BP_ISSUE_DT1 set)
Walnut ADU ordinance
Verified against Walnut Community Development Department's published ordinance on 2026-05-12. State law (CA Government Code §65852.2) overrides any locally-stricter rule.
Max detached ADU size
1,200 sqft (state default)
Max ADU height
16 ft / 18 ft with second-story setbacks
Setbacks
4 ft side / 4 ft rear (state minimum)
Hillside Standards
Apply on slopes over 10%
Local processing time
60 days for standard ADUs
Pre-approved standard plans
None city-specific
Drawings you'll need to submit
Type your address. See if you can build an ADU, what kind, and exactly how to permit it.
- Site plan (parcel layout + setbacks)
- Proposed floor plan
- Elevations (each side)
- Title 24 CF1R energy compliance
PermitPathLA generates the site plan free from your Walnut address. The other drawings come from your architect or plan firm — we list pre-approved options in the wizard.
Walnut watch-outs for ADU
Overlays that hit a meaningful share of Walnut lots
Hillside Standards~25% of parcels
Slopes over 10% trigger geotech + grading limits.
Local quirks
Walnut Valley Unified school fees apply
WVUSD charges school facility fees on ADUs over 500 sqft. Same district as Diamond Bar.
Mt. San Antonio College drives rental demand
Mt. SAC's 30,000+ student enrollment is one of the largest community college populations in California — significant local rental-demand driver.
Run your Walnut address through the wizard
We pull your parcel polygon from county GIS, apply Walnut ordinance + state baseline rules, generate the site plan, and walk you through the Walnut Community Development Department submittal. Free, no signup.