Diamond Bar · ADU permits
ADU permits in Diamond Bar
How to build a ADU in Diamond Bar: permit pathway through Diamond Bar Community Development Department, drawings required, local watch-outs, and a free address-level wizard for your Diamond Bar lot.
Diamond Bar context
Diamond Bar's ADU ordinance is in Diamond Bar 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
- Diamond Bar Community Development Department
- Median lot size
- 9,800 sqft
- ADU permits issued (2025)
- 150Source: Cal HCD Annual Progress Report 2025 (Table A2, BP_ISSUE_DT1 set)
Diamond Bar ADU ordinance
Verified against Diamond Bar 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 flat ADUs; longer for hillside
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 Diamond Bar address. The other drawings come from your architect or plan firm — we list pre-approved options in the wizard.
Diamond Bar watch-outs for ADU
Overlays that hit a meaningful share of Diamond Bar lots
Hillside Standards~35% of parcels
Slopes over 10% trigger geotech + grading limits.
Tonner Canyon / open-space adjacencies~10% of parcels
Parcels adjacent to protected open space face setback rules.
Local quirks
Walnut Valley + Pomona school district split
Diamond Bar is split between Walnut Valley Unified (most of the city) + Pomona Unified (small northern portion). Verify your district.
Hillside lots need geotech reports
Slopes over 10% trigger geotech / soils engineering report. Budget $3K-$8K and 4-8 weeks.
Run your Diamond Bar address through the wizard
We pull your parcel polygon from county GIS, apply Diamond Bar ordinance + state baseline rules, generate the site plan, and walk you through the Diamond Bar Community Development Department submittal. Free, no signup.