Any contractor who builds your ADU in Los Angeles County must hold an active California license, verifiable through the Contractors State License Board. Who oversees your permit depends on where your property sits: LA County Planning handles unincorporated areas only, while incorporated cities — including the City of Los Angeles — run their own permitting process that this guide doesn't detail, so confirm directly with that office. State ADU law was renumbered under SB 477 in 2024, and new energy code standards phase in starting January 1, 2026.
Who Regulates Your ADU Project, and What License Must Your Contractor Hold?
Two things determine how your ADU project gets built and inspected: which government agency has jurisdiction over your parcel, and whether your contractor holds an active license. LA County Planning covers unincorporated areas of Los Angeles County only — it has no authority over incorporated cities like the City of Los Angeles.
Separately, every contractor on your ADU needs an active California license, verifiable through CSLB — that holds true no matter which jurisdiction you're in.
Note: City of Los Angeles-specific permit fees, review timelines, and department contacts aren't covered by the sources behind this article. If your property is inside city limits, confirm current requirements directly with the Los Angeles Department of Building and Safety (LADBS) before you budget or sign a contract.
Is Your Property Under City of LA or LA County Planning?
Jurisdiction shapes more than paperwork — permit applications, plan check standards, and inspection schedules all differ, and a contractor who's never pulled a permit in your specific department can slow your project down. LA County Planning oversees unincorporated pockets of the county, places like Altadena or parts of the Santa Monica Mountains that sit outside any city boundary.
If your address falls inside the City of Los Angeles, or any other incorporated city in the county, a separate city process applies — one not detailed in the sources behind this guide. Don't guess: call or check online with the relevant city building department before finalizing plans.
Verifying an ADU Contractor's License Through CSLB
The Contractors State License Board has licensed and regulated California's construction industry since 1929, and it currently oversees roughly 285,000 contractors across 45 classifications. Before signing anything, look up your contractor's license number on the CSLB site and check that the classification matches the scope of work. An ADU build typically calls for a general building contractor license (B), though certain trade-specific work may fall under other classifications.
| Status | Count |
|---|---|
| Active licenses | 231,261 |
| Inactive licenses | 54,335 |
| Total contractors | 285,596 |
An inactive license means the contractor isn't currently authorized to perform work, so check status, not just that a license number exists.
Contract and Payment Rules That Apply to ADU Construction
Standard home improvement contract and payment rules apply to ADU construction, the same rules that cover residential solar installs and other home improvement work, per CSLB. If your ADU is part of a wildfire or other declared disaster rebuild, the law treats it as home improvement rather than new construction — that classification brings specific protections into play.
- Contractors must use a fixed-price contract for disaster-related rebuild work — time-and-materials or cost-plus billing isn't allowed.
- Down payments for disaster-related rebuild work are capped at $1,000 or 10% of the total contract price, whichever is less.
- Every payment after the down payment must be tied to work actually completed or materials actually delivered, and listed clearly in the contract.
Heads up: These fixed-price and down-payment limits apply specifically to disaster-related rebuild work. If your ADU isn't part of a declared disaster rebuild, confirm with your contractor and, if needed, CSLB which contract rules govern your project.
Current California ADU Law: SB 477 and the State ADU Handbook
As of March 25, 2024, SB 477 (Chapter 7, Statutes of 2024) renumbered the Government Code sections that govern State ADU and JADU law, according to HCD. If you're reading older articles or code references, the section numbers there may no longer match current law.
HCD's statewide ADU Handbook, last updated March 2026, is the reference point for current state requirements. Because both the Handbook and the underlying code sections have changed recently, check the current version directly rather than relying on older summaries — including this one, over time.
Energy Code Standards for a New ADU
Which energy code applies to your ADU depends on your permit submission date, not your construction start date. The California Energy Commission sets these standards on a fixed schedule.
| Standard | Effective date | Applies to permits submitted |
|---|---|---|
| 2022 Standards | January 1, 2023 | January 1, 2023 through the 2026 effective date |
| 2025 Standards | January 1, 2026 | On or after January 1, 2026 |
Confirm with your local building department which version applies to your specific permit submission — the cutover date can affect insulation, window, and mechanical system requirements your contractor needs to design around.
Wildfire Rebuild Support: Fee Waivers and Disaster Recovery Provisions
If you're rebuilding after the Eaton or Palisades fires, LA County Planning's Disaster Recovery Ordinance allows temporary housing and accessory structures on properties that had a legally established single-family residence, ADU, caretaker's residence, or farmworker dwelling unit before the fire.
Fee waivers and refunds are also available for rebuild permits, but eligibility is limited: you must have owned and lived on the property before January 7, 2025. Application steps and current eligibility details change, so confirm both directly with LA County Planning before assuming your rebuild qualifies.
What LA Homeowners Are Budgeting for ADUs
Among 83 ADU project requests submitted to Mr. Nailed It from Los Angeles County homeowners since 2024, the most common stated budget range was $100k–$150k, cited by 39% of respondents. Another 16% stated under $100k, and 14% stated $150k–$200k.
Note: This reflects what other homeowners in the area said they were planning to spend when submitting a project request — it's not a cost estimate, quote, or guarantee for your project.
Actual ADU costs depend on unit size, existing site conditions (grading, access, soil), utility connections (water, sewer, electrical panel capacity), and finish level. A contractor or licensed professional can walk your specific site and speak to how these factors affect your budget.
How to Choose and Vet an ADU Contractor in Los Angeles
- Look up the contractor's license on CSLB and confirm both the classification and active status before signing anything.
- If your ADU qualifies as disaster-related rebuild work, check the contract for fixed pricing and a payment schedule that matches the down-payment and progress-payment rules above.
- Confirm which jurisdiction — an incorporated city like the City of Los Angeles, or LA County Planning for unincorporated areas — governs your permit, and ask whether the contractor has pulled permits there before.
- Ask about site-specific cost drivers (utility hookups, grading, unit size) rather than relying on general budget ranges.
For a broader look at costs and permitting steps across LA County, see ADU Construction in Los Angeles: Complete Cost & Permit Guide. If you're considering converting an existing garage instead of building new, Garage Conversion to ADU or Living Space in Los Angeles covers that path separately.
Frequently asked questions
Is my property served by LA County Planning or the City of Los Angeles for ADU permitting?
It depends on whether your address is inside an incorporated city. LA County Planning only governs unincorporated areas of the county. If you're inside the City of Los Angeles or another incorporated city, that city's building department handles your permit instead — confirm directly with them.
How much can a contractor legally require as a down payment for ADU construction?
For disaster-related rebuild work, CSLB caps down payments at $1,000 or 10% of the total contract price, whichever is less, with remaining payments tied to completed work or delivered materials. If your ADU isn't part of a declared disaster rebuild, confirm which specific payment rules apply with your contractor or CSLB.
What license classification does an ADU contractor need, and how do I verify it?
Check the contractor's license directly on the CSLB website. CSLB licenses roughly 285,000 contractors across 45 classifications statewide, and you can confirm both classification and active status before signing a contract.
Do wildfire-rebuild contract rules apply to a standard ADU unrelated to fire rebuild?
The fixed-price and down-payment caps described by CSLB specifically apply to disaster-related rebuild work. Standard home improvement contract rules still apply to any ADU project, but confirm with your contractor or CSLB which specific provisions govern your situation if it isn't a disaster rebuild.
What energy code standards apply to an ADU built in 2026 versus one built under the 2022 standards?
Per the California Energy Commission, ADUs permitted from January 1, 2023 through the 2026 effective date fall under the 2022 Building Energy Efficiency Standards. ADUs permitted on or after January 1, 2026 must meet the 2025 Standards. Confirm which applies based on your permit submission date with your local building department.
Are there fee waivers for ADU permits tied to Eaton or Palisades wildfire rebuilds?
Yes, according to LA County Planning, fee waivers and refunds are available for owners rebuilding after the Eaton and Palisades wildfires who owned and lived on the property before January 7, 2025. Confirm current eligibility and application steps directly with LA County Planning.