This county guide helps prevent an expensive early mistake: using the wrong local rules. It offers planning details and may help route a referral. It does not approve a lot or provide building work.
Three city or county paths
City of Los Angeles
Sites inside the City use its land-use rules and the LADBS building process. Los Angeles City Planning posts adopted ADU rules apart from draft work. The City’s standard-plan program does not carry over to another city.
Another incorporated city
Long Beach, Pasadena and West Hollywood have their own review paths under state law. Each uses its own forms, plan programs and local rules. Check the city guide below. “LA area” is not one set of rules.
Unincorporated Los Angeles County
LA County Planning posts rules for unincorporated County land. Its current pages separate ADUs from JADUs and show paths by property type. A May 2026 single-family guide applies only to unincorporated County. It separates state and local paths.
Do not copy its allowances into an incorporated city without checking that city’s current material.
Establish city or county before property check
Start with an official address or lot tool. Confirm the assessor parcel number when useful. The assessor is not always the permit office. If the site is near a city line, ask the right office to confirm its area in writing.
Once the city or county is known, assemble the items below.
- current and planned building use;
- lot and building dimensions;
- easements and recorded constraints;
- access and work setup;
- fire, coastal, historic, slope or environmental context;
- parking and existing units;
- water, sewer and electrical companies; and
- any prior approvals or code cases.
These facts support a useful ADU early site review.
County geography does not equal utility territory
Water and power companies change across the County. Even a small city may have more than one water area. Do not use City of Los Angeles LADWP rules for Long Beach, Pasadena or West Hollywood. Check current bills and confirm the planned service with the utility.
Utility work affects both cost and schedule. A plan that fits zoning can still require panel, service, sewer, water, trenching or repair work.
County-wide cost claims need care
Labor, access, slope, soil, finishes and local rules vary. A County-wide price is a planning guide, not an estimate for an address. Use the Los Angeles ADU cost guide to separate design, fees and site work. Add the build, utilities, finishes, repairs and extra money for named risks.
Ask companies whether travel, city planning, special inspection or utility territory changes their quote.
Initial city pages
Long Beach
Long Beach now explains how it uses state ADU law. It has its own historic and coastal checks, pre-approved plans and filing steps. Read the Long Beach ADU construction guide.
Pasadena
Pasadena’s current rules limit the use of older standard plans after the 2026 code change. Read the Pasadena ADU construction guide.
West Hollywood
West Hollywood offers a free detached plan. The site must fit, and only some changes are allowed. The city also has its own utility setup. Read the West Hollywood ADU construction guide.
Use the county guide when your city has no separate page
Westside, South Bay, San Gabriel Valley and San Fernando Valley are useful area names, but they do not identify the office that reviews an ADU application. Start with the city or county responsible for the parcel.
This county guide links the available city guides and explains how to confirm the right authority elsewhere in Los Angeles County. A missing city page does not mean that providers cannot work there.
Company checks across cities and counties
A company may work in several cities but know some permit offices better than others. Ask for recent jobs reviewed by the same office. Ask who handled plans, the build, utilities and replies to correction notes. Verify the legal business in the CSLB database.
When comparing bids, use the same design and finishes. Keep local fees and work on separate, visible lines.
Use a city or county handoff sheet
When a project moves to a designer or builder, make a one-page handoff. Record the permit office and the official pages checked, with dates. Add known site limits, current utilities, earlier public contacts and open questions. Attach the lot records used. Mark any fact that has not been checked.
This stops a broad “Los Angeles project” label from following the job after the permit office is known. It also creates a clear record if anyone disputes the address, city line or public duty.
Frequently asked questions
Do LA County ADU rules apply in Los Angeles city limits?
No. County guidance for unincorporated property is not the City of Los Angeles rule source. Confirm the city boundary.
Does California State law make every city process identical?
No. State law confirms a framework, while local administration, forms, adopted provisions, overlays and utility processes can differ.
Are County standard plans valid in every incorporated city?
Do not assume so. Ask the actual permit office about the plan owner and current program status. Check the code year, allowed changes and site review.
Can one contractor handle projects throughout the County?
Some publicly claim broad coverage. But availability and local experience need direct verification for the project. A county page is not a coverage guarantee.