These rules apply to UNINCORPORATED Los Angeles County - communities like East Los Angeles, Altadena, Hacienda Heights, Rowland Heights, South Whittier, and Florence-Firestone - not the City of LA or the county's 88 incorporated cities, which each run their own ADU programs. The county's current ordinance (2025-0029, effective August 28, 2025) allows up to three accessory units on a single-family lot (attached ADU + detached ADU + JADU), caps new ADUs at 1,200 sq ft, and approves everything ministerially through the EPIC-LA portal under Title 22 Sec. 22.140.640. Note: where the county code conflicts with state ADU law (HCD flagged several provisions in December 2025), state standards control.
Zoning & Size Requirements [1][2]
Yes — unincorporated Los Angeles County allows ADUs. A detached ADU can typically be up to 1,200 sq ft under California state law and the County's zoning code.
See what this means for your lot — get 3 free quotes from Los Angeles County ADU builders →
| Where ADUs Are Allowed | Any lot zoned for single-family or multifamily residential use with an existing or concurrently built primary dwelling (Title 22 Sec. 22.140.640); state-exemption ADUs must be approved even in Very High Fire Hazard Severity Zones |
| Max Size (Detached) | 1,200 sq ft for new construction (conversions of existing detached structures have no maximum, +150 sq ft for ingress/egress); the 800 sq ft state-exemption ADU is approved with no local standards |
| Max Size (Attached) | 1,200 sq ft uniform limit since August 2025 (conversions entirely within the existing home have no maximum) |
| Max Size (JADU) | 500 sq ft within the single-family residence or attached garage (state standard) |
| Max Height | 25 ft for new-construction ADUs on single-family lots (state minimums of 16-20 ft still apply where a Community Standards District says less); 25 ft on multifamily lots |
| Max Units | Single-family lot: up to 3 accessory units - 1 attached ADU + 1 detached ADU + 1 JADU. Multifamily lot: converted ADUs up to 25% of existing units plus detached ADUs (state SB 1211 allows up to 8 detached, which controls over the county's 2). |
Setback & Parking Requirements [1][2]
Unincorporated Los Angeles County requires a rear setback of about 4 ft for a detached ADU, and parking requirements vary by unit size or location. Owner-occupancy is not required — you can rent it out without living on the property.
| Rear Setback | 4 ft for new construction; none for conversions or same-footprint rebuilds |
| Side Setback | 4 ft; 10 ft from a reversed corner lot line; no windows or doors within 3 ft of a property line |
| Front Setback | Standard Title 22 front setback - but an ADU of 800 sq ft or less may encroach into it if no other ground-level location exists (since Aug 2025) |
| Parking Required | None outside Very High Fire Hazard Severity Zones (and never for JADUs). In a VHFHSZ: 1 uncovered space unless exempt (near transit, ≤800 sq ft detached, conversion, historic district, car-share nearby). No replacement parking when a garage is converted |
| Owner Occupancy | Not required for ADUs. JADUs: the county requires owner occupancy via recorded covenant, but state AB 1154 (Jan 2026) bars that for JADUs with their own bathroom - state law controls |
| Min Lot Size | None - California law prohibits minimum lot sizes for ADUs |
Permit Process & Fees [3][4]
An ADU in unincorporated Los Angeles County is approved administratively — no public hearing — within the state's 60-day ministerial deadline from a complete application, with a 15-business-day completeness check since January 2026 (SB 543); permit fees are valuation-based through Regional Planning and Building & Safety - no flat rate; get an estimate through EPIC-LA before budgeting.
| Approval Process | Ministerial - no hearing. File a DRP Base Application with plot plan via the EPIC-LA portal for Regional Planning review, then plan check and permit through Public Works Building & Safety; JADUs need a recorded covenant |
| Review Timeline | the state's 60-day ministerial deadline from a complete application, with a 15-business-day completeness check since January 2026 (SB 543) |
| Permit Fees | valuation-based through Regional Planning and Building & Safety - no flat rate; get an estimate through EPIC-LA before budgeting |
| Impact Fees | Development impact fees are waived for ADUs 750 sq ft or less of interior livable space under California law (SB 543 clarified this from Jan 2026), and apply proportionally above that |
| Plan Check | Standard plan check via Building & Safety; using a pre-approved Standard Plan substantially shortens review |
| Pre-Approved Plans | Yes - the county's free Standard ADU Plans program (county catalog plus a private-designer catalog) provides pre-checked plans for unincorporated parcels |
Get Free ADU Quotes in Los Angeles County
Tell us about your project and we'll connect you with ADU builders serving Los Angeles County. Free, no obligation — you choose who to work with.
Takes about a minute.
Up to 3 independent local ADU builders — never more, and we tell them nothing you don't submit here.
Compare quotes, verify license & insurance, hire (or don't). No spam either way.
🔒 Your info is secure. We share it only with contractors quoting your project. No spam, no obligation.
Just browsing? Search ADU builders near you by ZIP code.
Construction Costs [5]
Building an ADU in unincorporated Los Angeles County typically costs $150,000-$350,000 (LA-metro market estimate) ($200-$400 (market estimate) per sq ft); a garage conversion runs $80,000-$180,000 (market estimate).
See what this means for your lot — get 3 free quotes from Los Angeles County ADU builders →
Construction costs in unincorporated Los Angeles County mirror the surrounding Inland Empire market. Rural parcels can cost more due to septic, well, access, and fire-hazard (WUI) requirements, so treat these as planning ranges and get local bids.
| Average Build Cost | $150,000-$350,000 (LA-metro market estimate) |
| Cost per Sq Ft | $200-$400 (market estimate) |
| Garage Conversion | $80,000-$180,000 (market estimate) |
| Prefab ADU (Installed) | $120,000-$270,000 (market estimate) |
Finance Your ADU Project
Most ADU projects are funded through HELOCs, construction loans, or cash-out refinancing. Compare rates from top lenders.
Some links on this page are affiliate links. We may earn a commission at no extra cost to you. Learn more
Rental Income Potential [6]
| Avg Rent (1 Bedroom) | $1,700-$2,400/mo (East LA and Florence-Firestone below Altadena/Hacienda Heights) |
| Avg Rent (2 Bedroom) | $2,100-$3,000/mo |
| Short-Term Rental | No - the county's short-term rental ordinance (effective September 2024) limits STRs to a host's primary residence and expressly bars ADUs and guesthouses from listing; the ADU ordinance separately requires rentals of 30+ days |
| Est. Annual ROI | 6-9% annual return (market estimate) |
Recent Law Changes
What's Changed Recently
- August 28, 2025: Ordinance 2025-0029 took effect - uniform 1,200 sq ft attached-ADU limit, 1,200 sq ft cap on detached ADUs on multifamily lots, state-exemption ADUs allowed in Very High Fire Hazard Severity Zones regardless of access, unpermitted structures may be converted, and sub-800 sq ft ADUs may encroach into front setbacks
- December 1, 2025: California HCD found the county ordinance partially non-compliant with state ADU law - state standards override the county code where they conflict
- January 1, 2026: SB 543 (15-business-day completeness review, impact-fee waiver 750 sq ft or less of interior livable space) and AB 1154 (no JADU owner-occupancy where the JADU has its own bathroom; JADU STR ban) took effect
- March 3, 2026: the Board accepted a $3.8M state grant funding ADU construction for 35-50 unincorporated-area households, prioritizing Eaton fire survivors in the Altadena area; AB 462 (Gov. Code 66328(b), eff. 10/10/2025) allows a certificate of occupancy for a DETACHED ADU before the main house, but only in a county under a Governor's emergency proclamation made ON OR AFTER February 1, 2025. The January 2025 Eaton/Palisades proclamation may fall outside that cutoff - confirm eligibility with LA County before relying on it. Attached ADUs are excluded entirely under 66328(c)
Tips for Building an ADU in Unincorporated Los Angeles County
- East LA, Altadena, Hacienda Heights, Rowland Heights, South Whittier, and Florence-Firestone are unincorporated - County rules apply, not City of LA rules
- Use the free Standard ADU Plans catalog to cut design costs and plan-check time on unincorporated parcels
- Keep the ADU at or 750 sq ft or less of interior livable space to avoid development impact fees entirely
- In fire-hazard zones (much of Altadena and the foothills), the 800 sq ft state-exemption ADU must be approved regardless of road-access standards - a strong fallback if the county flags your access
- Eaton fire survivors: ask the county about its ADU grant program. Do NOT assume AB 462 early occupancy applies - Gov. Code 66328(b) is limited to emergency proclamations made on or after February 1, 2025, and excludes attached ADUs. Get the county to confirm your parcel qualifies in writing before you plan around it
ADU Builders in Los Angeles County
Looking for an ADU builder in Los Angeles County? ADU projects need a contractor experienced with local zoning, the permit process, and utility connections — not every general contractor has built one. We match Los Angeles County homeowners with experienced local ADU contractors who provide free, no-obligation quotes. Getting at least three bids typically saves 20-40% on the same scope.
Cities Within Los Angeles County
If your property is inside one of these incorporated cities, follow that city's ADU code — not the County rules above:
Sources & References
All data on this page is sourced from official government records and verified market data. View our full methodology.
- LA County Regional Planning - ADU Ordinance Amendment certified ordinance (Ord. 2025-0029, eff. 8/28/2025) Planning Department — Accessed 2026-07-30
- LA County Regional Planning - Accessory Dwelling Units program page Planning Department — Accessed 2026-07-30
- LA County Regional Planning - ADU Ordinance Amendment FAQs Planning Department — Accessed 2026-07-30
- California HCD - ADU ordinance findings letter, County of Los Angeles (12/1/2025) Government Data — Accessed 2026-07-30
- Angi - ADU Construction Cost Data Market Data — Accessed 2026-07-30
- HUD Fair Market Rents Government Data — Accessed 2026-07-30
- California ADU Handbook - HCD Government Data — Accessed 2026-07-30
- LA County Regional Planning - Eaton Fire disaster recovery Planning Department — Accessed 2026-07-30
Frequently Asked Questions
What are the ADU rules in unincorporated Los Angeles County?
How much does an ADU permit cost in Los Angeles County?
Do I need owner-occupancy for an ADU in Los Angeles County?
Is my property in unincorporated Los Angeles County or inside a city?
How many ADUs can I build in unincorporated Los Angeles County?
Building in Unincorporated Los Angeles County?
Get free, no-obligation quotes from ADU contractors who work in Los Angeles County.
Get Free Quotes →