Altadena · ADU permits
ADU permits in Altadena
How to build a ADU in Altadena: permit pathway through LA County Public Works (Building & Safety), drawings required, local watch-outs, and a free address-level wizard for your Altadena lot.
Altadena context
Altadena is divided by Lake Avenue into east and west halves, with substantially different post-Eaton-Fire conditions. West Altadena was the harder-hit area; east Altadena saw lighter damage. Building permits are issued by LA County DPW Building & Safety at the Alhambra office (not at LADBS). ADU permitting in unincorporated LA County follows the state baseline (Gov Code §65852.2) implemented through LA County Code Title 22.140 — broadly similar to LADBS but with separate forms, fees, and inspectors. LA County also runs a streamlined rebuild permitting program for parcels with primary-residence loss in the Eaton Fire, including expedited ADU + primary-residence combined permits.
- Permit agency
- LA County Public Works (Building & Safety)
- Median lot size
- 8,500 sqft
- ADU permits issued (2025)
- 82Source: HCD 2025 total (1,278) distributed proportionally across 2024 per-area shares. 2024: 95.
Altadena ADU ordinance
Verified against LA County Public Works (Building & Safety)'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)
Permitting agency
LA County Public Works (Building & Safety), Alhambra office
Not LADBS. Different forms, fees, and inspectors. Online submission via EPIC-LA portal.
Local processing time
60 days from complete submittal (state-mandated)
LA County DPW typically meets the 60-day clock. Post-Eaton-Fire rebuild permits are on a separate expedited track.
Rebuild + ADU combined permits
Available for Eaton Fire affected parcels
LA County's rebuild program lets affected homeowners permit a primary-residence rebuild + an ADU concurrently on an expedited track. Specific eligibility through the LA County Recovery website.
Pre-approved standard plans
LA County A/B/C plans available (free, county-wide)
Three LA County pre-approved ADU plans usable in unincorporated areas. Free, similar to LADBS YOU-ADU.
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 Altadena address. The other drawings come from your architect or plan firm — we list pre-approved options in the wizard.
Altadena watch-outs for ADU
Overlays that hit a meaningful share of Altadena lots
Eaton Fire rebuild zone~40% of parcels
West Altadena and parts of east Altadena were significantly affected by the January 2025 Eaton Fire. LA County maintains a Recovery Permitting program with expedited review for affected parcels. ADUs are permitted alongside primary-residence rebuilds.
Very High Fire Hazard Severity Zone (VHFHSZ)~55% of parcels
Most of north Altadena (above Altadena Drive / Loma Alta) sits in the VHFHSZ. Triggers Chapter 7A construction (Class A roofing, ember-resistant venting, fire-rated assemblies) — adds roughly 7% to construction cost on top of base ADU build.
LA County Hillside Management Area~30% of parcels
Slopes over 25% in the northern foothills trigger LA County's Hillside Management Area rules — geotech / soils review, grading limits, and ridgeline-protection rules.
Local quirks
LADBS rules do not apply — this is LA County
If your contractor or designer assumes LADBS rules, stop and verify. Altadena is unincorporated LA County. Submittal goes to LA County DPW Building & Safety in Alhambra, not the LADBS Van Nuys or Downtown office. The codes are similar but the forms, fees, inspectors, and online portal (EPIC-LA, not LADBS PermitLA) are all different.
Post-Eaton-Fire rebuild lots have additional verification steps
If your lot had primary-residence fire damage in January 2025, the rebuild permit requires environmental clearance (debris removal verification, soil testing for ash residue) before the building permit is finalized. Most lots have already completed this through Phase 1 + 2 county debris removal — but always verify your parcel's status with LA County Recovery before paying for plans.
Altadena Library District is independent
Heads-up that the Altadena Library District is not part of LA County Library. It's a separately governed special district (a quirk dating to 1926). The two libraries on Mariposa and Lincoln are Altadena Library District; LA County Library cards are not interchangeable.
Pasadena Unified covers Altadena schools, not LA Unified
Even though Altadena is unincorporated, the school district is Pasadena Unified (PUSD) — not LAUSD. PUSD school facility fees apply to ADUs over 500 sqft.
Eaton Canyon Natural Area + trails are partially still in recovery
Eaton Canyon Falls trail and surrounding county trails were heavily damaged by the Eaton Fire. Sections have reopened in stages through 2025–26. If you're using Eaton Canyon access as a selling point for a future ADU tenant, verify current trail status with LA County Parks.
Run your Altadena address through the wizard
We pull your parcel polygon from county GIS, apply Altadena ordinance + state baseline rules, generate the site plan, and walk you through the LA County Public Works (Building & Safety) submittal. Free, no signup.