Pre-Approved ADU Plans in California: How They Work (2026)

A pre-approved ADU plan is a set of construction drawings for a detached ADU that a city or county has already checked against the building code, so review of your project can focus on your lot instead of the house. Every California city and county now has to run a preapproval program, and when a complete application uses a preapproved plan from the current code cycle, the agency has 30 days to approve or deny it. What a pre-approved plan is not: a house. You still need a site plan, energy and truss paperwork, a foundation that suits your soil, a builder (the counties strongly advise a licensed contractor) and the construction itself.

The short version: Pre-approved plans are drawings, not homes. State law gives agencies 30 days, instead of the usual 60, to decide a complete detached ADU application that uses a preapproved plan from the current code cycle. In our area, Monterey, Santa Cruz, San Benito and Santa Clara counties all run a program, and so do Salinas, San Jose, the City of Santa Clara, Gilroy and Morgan Hill. You still submit site-specific documents, and changing the plan usually costs you the fast track.

The state rule behind every program

The requirement comes from Government Code section 65852.27, the section created by Assembly Bill 1332. In plain English:

• Every agency needed a program by January 1, 2025 for preapproving ADU plans.
• Anyone can submit plans. Builders, architects, designers and homeowners can all apply, and the agency may charge the same permit fees it charges for an ADU of the same size.
• Approved plans get posted online with the applicant’s contact information, and a posting is not an endorsement. Agencies may also add plans they drew themselves or plans preapproved elsewhere in California.

The part that matters most to homeowners is the clock. Normally a complete ADU application on a lot with an existing home gets a decision within 60 days (see our guide to ministerial approval). Under 65852.27, the agency must approve or deny a complete application for a detached ADU within 30 days if it uses either:

1. A plan the agency preapproved within the current triennial California Building Standards Code cycle, or
2. A plan identical to one used in a detached ADU application the agency approved within that same cycle.

That code-cycle detail is easy to miss. California updates its building code every three years, and preapproved plans have to keep up. Since October 1, 2026, Salinas accepts only its 2025 plan sets for new permit applications, and Santa Cruz County is updating its plans to the 2025 code cycle.

Pre-approved ADU programs in our area

Here are the main programs and what each offered when we checked the official pages on November 2, 2026. Programs change, so confirm with the agency before you download or buy anything.

Swipe to see all columns

Santa Cruz County is unusually upfront about cost. Its pre-designed plans page lists approximate permit fees of about $5,000 for the 425 sq ft plan, about $6,000 for the 637 sq ft plan, and about $20,000 plus impact fees for the 998 sq ft plan, with school district and fire agency fees paid separately. Those are the county’s estimates, and they vary by parcel.

Each area’s rules go deeper than one table can. Our local guides cover Monterey County, Salinas, Santa Cruz County, San Benito County, unincorporated Santa Clara County, San Jose, Gilroy and Morgan Hill.

What you still have to submit

A pre-approved plan covers the house. Everything that ties the house to your lot is still on you, or on your builder. The official pages call for:

• A site plan showing where the ADU sits, its setbacks and its utility connections. Monterey County tells homeowners to hire a designer or architect for it (see do I need an architect for an ADU?).
• Title 24 energy calculations, plus solar, which Monterey County notes is mandatory for a new detached ADU. Our Title 24 guide explains that paperwork.
• A roof truss design from a truss manufacturer, stamped by a California licensed engineer, often as a deferred submittal.
• A foundation that fits your soil. The Monterey County and Santa Cruz County plans assume a slab-on-grade foundation using code presumptive soil values. If your site differs, you need a soils report and a custom foundation, and Santa Cruz County says its plans can’t be used when a different foundation is required.
• Stormwater, grading and septic details where needed. Monterey County says most septic properties under 1.25 acres will need an alternative system to add an ADU.
• A licensed contractor. The County of Santa Clara and San Jose both strongly advise having a licensed contractor or the plan vendor pull the permit.

Permit fees still apply too, even when the drawings are free.

Who qualifies, and who doesn’t

The fast track is narrower than the headlines suggest:

• Hazard zones. San Jose’s same-day path excludes geohazard, landslide, flood and Wildland-Urban Interface lots, and the County of Santa Clara’s expedited permitting excludes the same kinds of hazard zones. Gilroy’s pre-approved plans are limited to R1 and R2 zones and are not allowed in Hillside or designated Wildland Urban Interface areas.
• Historic properties and open code cases. The County of Santa Clara excludes both.
• An existing home. San Jose’s same-day path and the County of Santa Clara’s program require a residential lot with an existing single-family home or duplex, so empty lots fall outside them.
• Detached units only. The state’s 30-day rule covers detached ADU applications.
• Few or no changes. Santa Cruz County allows no modifications. The County of Santa Clara allows window and door changes and rotating its plans, and Monterey County treats changes beyond its built-in options as a new custom ADU.
• Special zones. Morgan Hill asks owners in historic, hillside, high fire severity or flood areas to talk with Planning before buying plans.

Free plan vs factory-built model

A free plan saves you design fees. It doesn’t build anything.

A free plan and a trusted local contractor can be a great fit on a simple, flat lot, especially for an owner who enjoys running a project. For most families, though, the drawings are the easy part. The real work is coordinating a designer, an engineer, a truss supplier, a contractor and every inspection, and that is what a done-for-you builder takes off your plate.

You can explore our 14 models and price a home in The ADU Designer by Framework First any time, no sign-up needed. Once your design is finalized, your selections are locked in: your model price, your add-ons and any promotion you qualify for are held for you.

How Framework First approaches pre-approved programs

Here is the straight answer. Our Six Sixty Duo (660 sq ft, 2 bedrooms, 1 bath) is on the City of Santa Clara’s published pre-approved ADU plan list, which we checked on November 2, 2026. Everywhere else, including San Jose, our homes go through standard ministerial review with a complete, site-specific plan set that our team prepares, submits and carries through plan check. Our San Jose permit guide shows that process step by step.

The identical-plan rule is still worth knowing: if an identical plan was used in a detached ADU application your city or county approved this code cycle, the agency must approve or deny a complete application within 30 days. Whether that applies depends on the jurisdiction and the exact plan, so it’s a fair question to ask any builder.

Your parcel’s specifics, from hazard zones and soils to utilities and real permit fees, get confirmed in the feasibility study: $497 for a standard lot or $997 for an empty lot. If your property can’t host an ADU, you get a full refund minus payment processing fees, and if you sign with us within 90 days, the fee is credited toward your build.

Frequently asked questions

Are pre-approved ADU plans free?

Often, for the drawings. Monterey, Santa Cruz, San Benito and Santa Clara counties all post their own plan sets for homeowners to download. Vendor plans, like those on San Jose’s list or in the Gilroy and Morgan Hill galleries, are priced by the designer. Permit fees, the site plan, energy calculations, truss design, foundation and construction are still on top.

Do pre-approved plans make the permit faster?

They can. State law gives the agency 30 days instead of 60 for a complete detached ADU application using a current preapproved plan, and San Jose may issue permits the same day as the plan review meeting. The catch is the word complete: soils, hazard zones or utility routing can still add time.

Can I change a pre-approved plan?

Only a little. Santa Cruz County allows no modifications, and the County of Santa Clara allows only small changes like windows, doors and rotating its own plans. Larger changes usually make it a custom ADU with full plan review.

Can a prefab ADU be pre-approved?

Yes. Anyone can submit plans for preapproval, and the County of Santa Clara notes that pre-approved plans may be prefabricated or conventionally built. A listing means the agency checked the drawings, not that it endorses the company. Our Six Sixty Duo is on the City of Santa Clara’s pre-approved list; in other cities and counties our homes go through standard ministerial review.

Does Monterey County have pre-approved ADU plans?

Yes. Monterey County offers three pre-designed detached plans, 515, 749 and 1,200 sq ft, in two exterior styles, for parcels where the county issues the permit. The 1,200 sq ft plan requires impact fees. Inside Salinas city limits, the city runs its own program with four detached plans.

Rather see a finished home on your lot than a drawing set? Design one in The ADU Designer, then book a free Online Property Analysis and our team will walk through what your city or county requires.