LA County Pre-Approved ADU Standard Plans (Plan A / B / C)
LA County's Free Pre-Approved ADU Plans Plan A, B & C: What Homeowners Need to Know If you own a home in unincorporated Los Angeles County and you've been d...
Written by 1-800-ADU-Pros
LA County Pre-Approved ADU Standard Plans (Plan A / B / C)
LA County's Free Pre-Approved ADU Plans (Plan A, B & C): What Homeowners Need to Know
If you own a home in unincorporated Los Angeles County and you've been dreaming about adding an accessory dwelling unit (ADU), there's a program that can save you real time and money: LA County's Pre-Approved ADU Standard Plans. The County offers three complete ADU designs you can download for free, and because they're already vetted for code compliance, they skip the slow structural plan-check that bogs down most custom ADU permits.
Here's how the program works, who it's for, and the traps to avoid.
What the program actually is
LA County Public Works (Building and Safety), working with the Department of Regional Planning, has created a small catalog of ADU designs that both agencies have already reviewed and approved for compliance with the Building, Residential, and Green codes. In plain English: a County engineer has already signed off on the building itself.
There are three County-owned plans, and they're free to use:
- Plan A — 1,200 sq ft, 3 bedrooms, 1 bathroom
- Plan B — 1,200 sq ft, 2 bedrooms, 1 bathroom
- Plan C — 800 sq ft, 1 bedroom, 1 bathroom
Because the design is pre-cleared, you don't go through the usual structural design review on the building. That's where the time savings come from.
Who it's for (and who it's not)
This is a County program for unincorporated LA County — places where the County, not a city, issues your building permit. If your property sits inside an incorporated city like the City of Los Angeles, Pasadena, or Long Beach, this catalog does not apply. The City of Los Angeles runs its own separate standard-plan program (you may have seen "YOU-ADU"), and the two catalogs are not interchangeable. A County plan can't permit a city project, and vice versa.
Not sure which you're in? Check your property's jurisdiction before you do anything else — it determines the entire process.
The big catch: you can't change the plans
This is the rule people miss. The pre-approved plans cannot be revised and must be permitted as designed. You're allowed to orient the unit in any direction and mirror (flip) the floor plan to fit your lot — but that's it. No moving walls, no resizing, no extra window. If you want a custom layout, this program isn't your path.
How to file, step by step
- Pick a plan (A, B, or C) and download the set for free from the County's pre-approved ADU page.
- File a Regional Planning base application and get a site-specific plot plan approved — this shows the plan placed on your actual lot with correct setbacks.
- Submit a Residential Building Permit application with your approved plot plan, the plan set, and Title 24 energy calculations. Do this at a County Building and Safety district office or online through EPIC-LA (unincorporated areas only).
- Receive your agency referral sheet, which lists the outside approvals your site needs.
- Have the plans reviewed and approved.
- Submit all required external agency approvals (Fire, Public Health/septic, utilities, etc.).
- Pay your fees through EPIC-LA, and the Building Official issues your permit.
After that, request your first inspection within 12 months, then keep inspection activity going at least every 180 days so the permit doesn't expire.
What it costs
The plans are free. But "free plans" doesn't mean "free permit." You'll still pay standard County permit and plan-review fees, Regional Planning fees, school fees, and any outside-agency or utility charges — all based on your project's valuation and scope, paid through EPIC-LA. The County doesn't post a single flat number, and for a unit this size the permit and plan-check fees commonly run into the low-to-mid four figures. Confirm exact amounts with your district office.
Common pitfalls to avoid
- Don't confuse the County and City catalogs — they don't cross over.
- Don't assume "pre-approved" means "no permit." You still file a full permit and pay fees; what you save is the structural plan check on the design.
- Don't forget the plot plan. The pre-approval covers the building, not your lot — Regional Planning still has to approve the placement.
- Don't underestimate the agency referral step. Site-specific approvals can become the real bottleneck.
- Don't let the permit lapse. Miss the 12-month or 180-day inspection windows and you can lose it.
Bottom line
For an unincorporated-County homeowner who's happy with a standard 1-, 2-, or 3-bedroom ADU, the Pre-Approved Standard Plans program is one of the fastest, cheapest ways to get permitted — as long as you can live with the design exactly as drawn.
Sources: LA County Pre-Approved ADU Standard Plans, LA County Planning — ADUs, City of LA Approved Standard Plans (for contrast).
Reference card
- Official number: Standard ADU Plans — County Catalog: Plan A, Plan B, Plan C
- Issuing body: Los Angeles County Public Works, Building and Safety — jointly with LA County Department of Regional Planning
- What it is: A free catalog of three County-owned ADU designs (Plan A, B, and C) that have already been reviewed and pre-approved by both LA County Regional Planning and Public Works Building and Safety for compliance with the Building, Residential, and Green codes. Because the structural/code design has been vetted in advance, choosing one of these plans removes the back-and-forth structural plan check on the building design itself, which is what slows most custom ADU permits. The three plans are: Plan A — 1,200 sq ft, 3 bed / 1 bath; Plan B — 1,200 sq ft, 2 bed / 1 bath; Plan C — 800 sq ft, 1 bed / 1 bath. The plans are downloadable at no cost. This is a separate, non-interchangeable catalog from the City of Los Angeles's own standard-plan program (e.g. YOU-ADU) — a County plan cannot be used to permit a project inside an incorporated city, and vice versa.
- Who needs it: For homeowners in UNINCORPORATED Los Angeles County — areas where the County (not a city) issues your building permit, submitted at a County Building and Safety district office or online via EPIC-LA. If your property is inside an incorporated city (City of Los Angeles, Pasadena, Long Beach, Santa Monica, etc.), this County catalog does not apply — you would use that city's own program or a custom set of plans. You can skip this catalog if you want a custom-designed ADU, a different size/layout than the three offered, or any modifications, because the plans cannot be altered. Best fit: an unincorporated-County homeowner who wants a standard 1- to 3-bedroom detached ADU and wants to move faster and cheaper than a custom design.
- Fees: The plans themselves are FREE (County-owned catalog). You still pay standard County permit and plan-review fees, plus Regional Planning, school, and any outside-agency/utility fees — these are based on valuation and project scope, paid through EPIC-LA, and are NOT waived by using a pre-approved plan. The County does not publish a single flat fee on the pre-approved-plan page; total permit/plan-check costs commonly land in the four-figure range for a project this size (third-party 2026 estimates put LA-area ADU plan-check + permit fees roughly in the $1,300-$8,000+ band depending on valuation and location — confirm exact numbers with your district office). Future privately designed plans in the catalog will be available for purchase rather than free.
- Timeline: Faster than a custom ADU because the building design itself is already approved, but not instant — the Regional Planning plot plan, agency referrals, and outside-agency approvals still take time. Plan on weeks-to-a-few-months for the County review path, versus the typical 4-6 months (sometimes longer) for a fully custom ADU. After the permit issues, you must request your first inspection within 12 months, then maintain inspection activity at least every 180 days or the permit can expire.
Requirements
- An approved site-specific plot plan from LA County Regional Planning showing the chosen plan placed on your specific lot (setbacks, orientation, etc.)
- The downloaded pre-approved plan set (Plan A, B, or C) — used exactly as designed; no revisions permitted
- Title 24 energy calculations for the project
- A completed Regional Planning base application
- A Residential Building Permit application (New Construction)
- All external/outside agency approvals identified on the County's agency referral sheet (e.g. Fire, Public Health/septic, Flood, utilities — varies by site)
How to file
- Pick your plan (A, B, or C) and download the free plan set from the LA County Building and Safety pre-approved ADU page. You may orient the unit any direction and mirror/flip the floor plan, but you cannot otherwise change it.
- File the Regional Planning base application and get a site-specific plot plan approved, showing the chosen plan placed on your actual lot.
- Submit a Residential Building Permit application with your approved plot plan, the pre-approved plan set, and Title 24 energy calculations — at a County Building and Safety district office or online via EPIC-LA (unincorporated areas only).
- Receive the agency referral sheet, which lists the outside agency approvals your site requires.
- Have the plans reviewed and approved by the County.
- Obtain and submit all required external agency approvals.
- Pay the permit fees through EPIC-LA; the Building Official issues your permit.
- Request inspections online — start within 12 months of permit issuance, then keep activity going at least every 180 days so the permit stays valid.
Common pitfalls
- Confusing the County catalog with the City of Los Angeles catalog — they are separate and non-interchangeable. A County plan cannot permit a project inside an incorporated city.
- Assuming the plans are editable. They cannot be revised and must be permitted exactly as designed; the only allowed changes are orientation and mirroring/flipping the floor plan.
- Thinking 'pre-approved' means 'no permit needed.' You still file a full building permit, a Regional Planning base application, and pay fees — the savings is on structural plan check of the design, not the whole process.
- Forgetting the site-specific plot plan from Regional Planning — the pre-approval covers the building, not your lot. You still need an approved plot plan matching your property's setbacks and zoning.
- Skipping the agency referral sheet. Site-specific approvals (Fire, Public Health/septic, Flood, utilities) can become the real bottleneck even when the building design is pre-cleared.
- Letting the permit lapse — no inspection within 12 months, or a gap longer than 180 days between inspections, can void it.
- Picking a plan that doesn't fit the lot's size, setbacks, or slope before checking with a planner — the design can't be trimmed to fit.
Sources
Pre-ADU Checkup — $499 — Get finalized permits, a pre-ADU checklist, and an on-site feasibility visit. Homeowners save $1,000s by doing this before engaging a contractor.