ADUs in Unincorporated Los Angeles County

If your parcel sits outside city limits — in West Carson, the unincorporated pockets around Torrance and Harbor City, Athens, Lennox, or Del Aire — Los Angeles County permits your ADU, not the city in your mailing address.

A mailing address is a postal label, not a jurisdiction. Thousands of South Bay parcels carry a Torrance or Gardena mailing address while sitting on unincorporated county land, and those parcels follow a different permitting path: a county plan library, a county portal, and county counters. This guide covers how to tell which government you belong to, what the county allows, how the county’s free pre-approved ADU plans work, and the exact steps a county ADU permit follows.

First Question: Is Your Parcel in a City at All?

Unincorporated land is everything in Los Angeles County that lies outside the boundaries of its 88 cities. Near Torrance and Gardena, the unincorporated map includes:

• West Carson. An unincorporated community of more than 20,000 people whose ZIP code, 90502, is designated a Torrance mailing address. If you live there, you are in the county — not Torrance, and not Carson.
• Unincorporated Torrance and Harbor City pockets. LA County Public Works confirms there are unincorporated areas of Torrance and Harbor City; since July 6, 2026, their Building and Safety permits are managed by the county’s Lomita District Office (below).
• Athens and Westmont, just north of Gardena and east of Hawthorne; Lennox, north of Hawthorne; Del Aire, between El Segundo and Hawthorne; and El Camino Village, south of Hawthorne — all unincorporated communities surrounded by cities.

How to check your parcel: look your address up in the County Department of Regional Planning’s online zoning/GIS viewer, or check your property tax bill — both identify the jurisdiction. If the permitting agency is Los Angeles County, your parcel is unincorporated, whatever your envelopes say. Getting this wrong costs real time: a city building department cannot accept an application for a county parcel, and the county cannot permit a city one.

County vs. City: Who Permits Your ADU?

Either way, approval is ministerial: a code-compliant ADU is approved by right, with no public hearing and no neighbor vote. Under state law, the agency must approve or deny a complete ADU application within 60 days — and, as the next section explains, a county pre-approved plan can cut that clock in half.

LA County’s Pre-Approved ADU Plans

For unincorporated parcels, the county runs a pre-approved plan program that most homeowners never hear about. The headline facts:

• Three county-owned standard plans, free to download. Plan A and Plan B are 1,200-square-foot, one-story designs; Plan C is an 800-square-foot design. The county also lists additional plans owned by private design firms, which you purchase from the firm.
• The building is already plan-checked. “Pre-approved” means the construction drawings have passed county review once, for everyone. Your application is reviewed for your site — the drawings themselves are not re-reviewed from scratch.
• A faster decision clock. California law requires an application that uses a pre-approved plan to be approved or denied within 30 days of a complete application, instead of the standard 60.
• A garage-conversion track, too. The county also promotes converting an existing garage using standardized notes and details and an expedited process for qualifying single-story conversions.

What pre-approved does not cover. The plan is only the building. Your project still needs site-specific work before a permit issues:

• A site-specific plot plan showing the unit on your actual lot, submitted to Regional Planning with a base application for review and approval;
• Title 24 energy calculations for your project;
• Utility connections — water, sewer or septic, and electrical service for the new unit;
• Agency clearances the county refers you to during plan check (fire, sanitation, water, and similar), gathered from the agency referral sheet the plan checker gives you.

The standard plans are fixed designs — the savings come from skipping custom design fees and the design portion of plan check, not from skipping the site work. The county’s official program page, with the plan downloads and step-by-step instructions, is here: LA County Building and Safety — Pre-Approved ADU Standard Plans.

Key County Standards for Unincorporated Parcels

LA County’s ADU ordinance (Title 22) applies California’s statewide standards in unincorporated areas. The numbers that shape most projects:

• Size. A detached ADU can be up to 1,200 square feet (and as small as 150). An attached addition can add up to 50% of the main home’s living area, to a maximum of 1,200 additional square feet. A junior ADU (JADU) of up to 500 square feet can be carved out within the existing home.
• Setbacks. A new detached ADU needs no more than 4-foot side and rear setbacks. Converting an existing structure — a garage, for example — in the same location and dimensions requires no new setbacks. Plan on at least 6 feet of separation between a detached ADU and the main house.
• Height. State law guarantees a detached ADU at least 16 feet — 18 feet within a half-mile of a major transit stop, plus 2 more feet to match the main home’s roof pitch. An attached ADU can reach 25 feet or the height limit that applies to the main home, whichever is lower.
• Parking. In the most common situations the county cannot require ADU parking at all — within a half-mile of public transit, in a historic district, when the ADU is created within the main home or an existing accessory structure, when on-street parking permits aren’t offered to the ADU’s occupant, or near a car-share vehicle. A garage conversion never requires replacement parking.
• Owner occupancy. None for a standard ADU — California law prohibits the requirement, so both the main home and the ADU can be rented. JADUs are the exception: the owner must live in the main home or the JADU.
• Overlays still apply. Hillside management areas, high fire-hazard zones, and community standards districts can adjust the numbers above (hillside parcels, for example, face a tighter size cap). A parcel-level feasibility check confirms which standards actually govern your lot.

The County Permit Path, Step by Step

This is the sequence LA County Public Works publishes for unincorporated ADU permits — the same path whether your plans are pre-approved or custom:

1. Confirm jurisdiction and zoning. Verify the parcel is unincorporated and check its zoning with the Department of Regional Planning. Choose your plans — a county pre-approved standard plan or a custom design.
2. Site-specific plot plan. Submit a Regional Planning base application with a completed site-specific plot plan showing the ADU on your lot, for review and approval.
3. Building permit application. File a Residential New Construction building permit application at your Building and Safety district office or online through EPIC-LA, uploading the approved plot plan set, the full plan package, and Title 24 energy calculations. Plan check fees are paid at this stage.
4. Agency referral sheet. The plan check engineer hands you a referral sheet listing every county, state, or federal agency whose approval you need before the permit can issue.
5. Plan check approval. Building and Safety checks and approves the plans.
6. Agency approvals submitted. You collect and submit the approvals from the referral sheet.
7. Permit issuance. Pay the remaining permit fees through EPIC-LA; when the Building Official issues the permit, construction can start.
8. Build and inspect. Request inspections through EPIC-LA as work progresses — the first within 12 months of issuance, with follow-up inspections at least every 180 days so the permit doesn’t expire.

ADU Cities runs this whole sequence for county clients: jurisdiction check, plot plan, EPIC-LA filings, agency clearances, and the build itself.

This page is a plain-language summary for homeowners, drawn from the LA County Department of Regional Planning’s ADU materials, LA County Public Works Building and Safety (including its pre-approved ADU plans page), LA County Code Title 22 §22.140.640, and California’s ADU statutes (Government Code §§66310 et seq.). It is not legal advice; the county’s standards for your specific parcel control what can actually be built. Official sources: LA County Planning — Accessory Dwelling Units · EPIC-LA permit portal.

Work With ADU Cities

Building on County Land? You Need a Contractor Who Works the County Counter

County ADU projects run on county rails — EPIC-LA filings, Regional Planning plot plans, district-office plan check. ADU Cities is a design-build ADU contractor that carries unincorporated-parcel projects from the jurisdiction check through final inspection.