What are preapproved ADU plans?

Plan sets that a city has already reviewed and approved for code compliance, published on its website for anyone to use. Because the structural review is done, an application using preapproved plans must be approved or denied within 30 days. AB 1332 required every California jurisdiction to run such a program starting January 1, 2025.

Can I use a preapproved plan from another city?

Usually no. Preapproval is granted by a specific jurisdiction and reflects that jurisdiction's review, so a plan preapproved in one city normally needs review in the next. There are exceptions: the City of San Diego accepts plans preapproved by San Diego County, Chula Vista, and Encinitas. Ask your planning counter whether they accept plans from neighbouring jurisdictions, because most people never think to.

How big can my ADU be?

If your city has a compliant ADU ordinance, its size cap must still allow at least 850 square feet, or 1,000 square feet with more than one bedroom. Without a compliant ordinance, the fallback is 1,200 square feet for new detached construction. Converting existing space is not subject to size caps at all.

What has to be in a plan set for plan check?

At minimum: a site plan showing setbacks and utilities, floor plans, elevations, a foundation plan, structural details, electrical and plumbing layouts, and Title 24 energy compliance documentation. A soils report is commonly required for new detached construction.

ADU Plans & Floor Plans (2026): Layouts + Preapproved Programs

Where do ADU plans come from?

You have three options: use a preapproved plan from your city’s published program, buy a stock plan set from a vendor, or commission a custom design. Since January 1, 2025, every California jurisdiction has been required to run a preapproved ADU plan program under AB 1332. Applications using preapproved plans must be approved or denied within 30 days, compared to the 60 days a standard ADU application gets.

Most ADU guides treat plans as a shopping problem: here are some pretty layouts, pick one. The more consequential decision is which approval path your plan set puts you on, because that’s what determines whether you’re building this year or next.

Common layouts by size

Interior layout is mostly a function of how many fixed wet walls you can afford and where the door goes. These are the configurations that recur.

Typical ADU layouts
Size	Config	What fits	Notes
150 to 400 sq ft	Studio	Combined living and sleeping, 3/4 bath, kitchenette	California allows efficiency units as small as 150 sq ft
400 to 600 sq ft	Studio or 1 bed	Separated bedroom, full bath, galley kitchen	Under the 500 sq ft school-fee threshold at the low end
600 to 750 sq ft	1 bed	Real bedroom, full kitchen, living area, storage	Stays under the 750 sq ft impact-fee exemption
750 to 1,000 sq ft	2 bed	Two bedrooms, one or two baths, in-unit laundry	Impact fees now apply, prorated
1,000 to 1,200 sq ft	2 to 3 bed	Family-scale layout	Only if your local cap allows it

The three layouts that recur at small sizes. Note the shared plumbing wall in each.

Two design notes repeat across every good small layout.

Put the wet walls together. Kitchen and bathroom plumbing on a shared wall is meaningfully cheaper than plumbing at opposite ends of the building. In a 500-square-foot unit this is one of the few decisions that moves the budget by thousands rather than hundreds.

Buy ceiling height instead of floor area. A 400-square-foot unit with a vaulted ceiling and a clerestory reads far larger than one with an eight-foot flat ceiling, and vertical volume is cheaper per perceived square foot than horizontal area. You’re not paying for more foundation or roof footprint.

Preapproved plans: the part nobody tells you about

AB 1332, codified at Government Code § 65852.27, took effect January 1, 2025. It requires every local agency in California to develop a program that accepts ADU plan submissions for preapproval, approves or denies them, and posts the approved plans and the applicant’s contact information on the agency’s website.

The payoff for you: when you apply for a permit using preapproved plans, the agency must approve or deny within 30 days of a complete application.

That’s the whole pitch. The structural and code review that normally consumes the bulk of plan check has already happened. What remains is site-specific: does this plan fit on this lot, with these setbacks, connected to these utilities.

Programs we have verified

There is no statewide index, so we are building one. Every entry below was checked against the jurisdiction’s own website on the date shown, not taken from a directory site.

California preapproved ADU plan programs, verified directly
Jurisdiction	Model	Cost	Sizes offered	Modifiable?
City of Los Angeles	Mixed	Some free	28 plans, 200 to 1,200 sq ft	Varies by plan
LA County (unincorporated)	Agency-owned	Free	800 and 1,200 sq ft, 3 plans	No
San Diego County (unincorporated)	Agency-owned, partial	Free	600 to 1,200 sq ft, 6 plans	Yes, CAD files provided
Sacramento County (unincorporated)	Agency-owned	Free	460 to 1,184 sq ft, 5 models	Barely
City of San José	Vendor	Buy from vendor	476 to 795 sq ft, 4 vendors	No
City of San Francisco	Vendor	Buy from designer	Designed for 25 ft lots	No
City of Long Beach	Agency-owned	Check	Single-storey, under 1,200 sq ft	No
City of Fresno	Agency-owned	Check	5 plans, 3 elevations each	Elevation choice only
City of Santa Ana	Agency-owned	Check	Check current list	Check
City of San Diego	Reciprocal	Varies	Accepts other agencies' plans	Depends on source
Orange County	Check current list	Check	Check	Check

Checked August 2026. The first seven rows were read directly from the agency's own page; the rest are confirmed programs where we have the official URL but have not yet read the full detail, so treat those as a starting point. Unincorporated county programs apply only outside incorporated cities.

Direct links:

Three different models hide behind the same phrase

Nobody explains this, and it changes what “preapproved” actually gets you.

Agency-owned and fixed. The jurisdiction commissions plans, owns them, and publishes them free. LA County and Sacramento County both work this way. You download a PDF at no cost. The catch is that the plan is fixed. LA County states its plans “cannot be revised and must be permitted as designed,” allowing only mirroring and orientation. Sacramento is nearly as strict: outside adding electrical receptacles, lights, or switches, the plans cannot be modified, and the roof trusses in particular cannot be altered at all.

Agency-owned and partial. San Diego County publishes six plans free and supplies editable CAD files alongside the PDFs. Their plans are described as approximately 85% complete, with a checklist of project-specific information you fill in. More work for you, far more flexibility.

Vendor. The jurisdiction reviews plans submitted by private companies, architects, and contractors, then lists the approved vendors. San José and San Francisco both work this way. You buy the plan from the vendor, so preapproval saves review time rather than design cost. San Francisco charges designers a $1,519 flat fee per plan submitted for review, which is worth knowing because that cost reaches you in the plan price.

Ask which model applies before you budget. The word “preapproved” is doing very different work in each case.

Two costs the programs do not put in the headline

Solar, on anything but the smallest unit. Sacramento County requires a photovoltaic system on its three larger models, meaning the 870, 1,000, and 1,184 square foot plans, but not on the 460 square foot studios. The applicant supplies the PV plans, and it is a separate permit at additional cost. This is easy to miss and it is not small.

Fire jurisdiction review. Sacramento requires a separate submittal to your local fire jurisdiction, with its own potential review, permit, and fees. That is on top of the building permit.

Sacramento also confirms the state threshold plainly on their own page: ADUs greater than 750 square feet are subject to impact fees. Their 870, 1,000, and 1,184 square foot models all cross it. Their 460 square foot studios do not.

One city accepts other agencies’ plans

We wrote above that preapproval is jurisdiction-specific. That is the general rule and it holds almost everywhere, but San Diego is the exception worth knowing about.

The City of San Diego accepts preapproved plans from other jurisdictions, including San Diego County, Chula Vista, and Encinitas. A plan approved next door can be used inside the city.

This is unusual and it is worth asking about wherever you are, particularly if you sit next to a county or a neighbouring city with a strong program. The question to put to your planning counter is simple: “Do you accept preapproved plans from any neighbouring jurisdiction?” Most will say no. It costs nothing to ask, and where the answer is yes it can save you the entire design step.

Preapproval expires, and geography disqualifies

Two things that catch people out and that no program advertises.

Preapproval is tied to the code cycle. San Francisco states that a pre-approval is valid only during the current code cycle. When California updates its building code, plans have to be resubmitted and re-approved against the new one. A plan that was preapproved two years ago may not be preapproved today. Check the date on any list you are working from, including this one.

Your lot may be disqualified regardless of the plan. Every program we checked excludes certain ground conditions. San Francisco excludes slope protection areas, slope and seismic hazard zones, landslide and liquefaction zones, Maher zones, and flood zones. San José excludes geohazard, landslide, flood, and Wildland-Urban Interface areas.

Those exclusions exist because a preapproved plan assumes an ordinary foundation on ordinary ground. If your site is not ordinary, the structural assumptions do not hold and you need site-specific engineering anyway. Check your address against your jurisdiction’s hazard maps before you get attached to a plan.

What a preapproved plan does not cover

A preapproved plan covers the building. It never covers your lot.

Every program in the table still requires site-specific work. LA County requires an approved site-specific plot plan from Regional Planning plus Title 24 energy calculations. Sacramento requires a scaled plot plan showing property lines, all structures, easements, and utility runs, plus a signed hold harmless agreement. San José requires site-specific documents showing location, utility connections, and setbacks.

Budget for that work. The saving is in structural review, not in the whole submittal.

Two programs worth studying if you want speed

Long Beach approves its pre-approved ADU plans over the counter, and states a construction permit can be issued the same day. The program covers single-storey freestanding units under 1,200 square feet.

San José is worth studying if you want speed

Their program is the most aggressive in the state on turnaround. If your site-specific documents are accurate and complete, the city states permits may be issued the same day as the scheduled plan review meeting.

The eligibility conditions are specific, and they make a useful checklist anywhere:

Lot zoned residential with an existing single-family home or duplex
Lot not in a geohazard zone, landslide zone, flood zone, or Wildland-Urban Interface area

That WUI exclusion catches a lot of California property and is worth checking against your own address early, wherever you live.

How to actually find them

There is no statewide index. Each jurisdiction posts its own, and the quality of that posting varies from a searchable database to a single PDF buried three clicks deep.

The reliable approach:

Search your city’s site for “preapproved ADU plans” or “pre-approved ADU.”
If nothing turns up, search for “AB 1332” plus your city name. Many jurisdictions titled the page after the bill.
Call the planning counter and ask specifically for “the preapproved ADU plan program required under AB 1332.” Naming the statute tends to produce a faster answer than naming the concept.
If your city has no program, that’s a compliance failure on their part, and worth saying so politely in writing.

The catch

Preapproval is jurisdiction-specific. A plan preapproved in Pasadena is not preapproved in Long Beach. Vendors who sell into the California market often pursue preapproval across many cities, so a given design may be available in yours, but confirm it against your city’s own posted list rather than the vendor’s marketing.

Preapproval also covers the building, not your lot. You still need a site plan, and site conditions such as slope, soils, utility distance, easements, and fire access can still complicate things.

Stock plans vs. custom design

Stock plans are the middle path: a complete, buildable set for a few thousand dollars rather than the tens of thousands a custom design costs. The trade-off is that a stock set still needs local plan check unless it happens to be preapproved in your jurisdiction, and it may need modification for your site’s soils or seismic conditions, which means paying an engineer anyway.

Custom design earns its cost in exactly two situations: a difficult site that no stock plan fits, or a specific functional requirement such as aging-in-place accessibility, a workshop, or a particular relationship to the main house that off-the-shelf layouts don’t serve.

For most flat, rectangular lots with a standard utility layout, custom design is a large expense buying a small amount of differentiation.

What a plan set has to include

Plan check rejects sets for missing content constantly, and every rejection costs weeks. A complete submittal generally includes:

Site plan, showing property lines, setbacks, existing structures, the new unit’s footprint, utility routing, and drainage
Floor plans, dimensioned, with room labels and fixture locations
Elevations for all four sides, with heights called out against the applicable limit
Foundation plan, sized to the soils report
Structural details and calculations, stamped by an engineer where required
Electrical plan, including service load calculations, which is where an undersized main panel gets discovered
Plumbing plan, covering supply, waste, vent, and the connection point to the existing lateral
Title 24 energy compliance, meaning California’s energy code documentation and any required solar
Soils report, commonly required for new detached construction

The two that most often surprise homeowners are the electrical load calculation and the soils report. Both can force real design changes, and both are cheaper to run early than to discover in plan check.

What to do first

Before you spend money on a design:

Check your city’s preapproved list. If something on it fits your lot and your needs, you have just saved months and a design fee.
Confirm your local size cap. It must permit at least 850 square feet, or 1,000 with more than one bedroom, but knowing the actual number shapes the plan.
Decide whether you’re staying under 750 square feet. The impact fee exemption at that threshold is worth real money. See ADU costs.
If you’re converting rather than building new, size caps don’t apply to you at all, and the plan work is a different exercise. Start with garage conversion.

ADU Plans: Layouts by Size and How Preapproved Plans Cut Your Permit Time