California homeowners know that adding an accessory dwelling unit (ADU) can unlock significant value — whether it’s rental income, multigenerational living space, or future resale appeal.
But if you’ve ever started the ADU design and permitting process, you already know it can feel confusing, expensive, and slow.
That’s why cities and counties across California are rolling out pre-approved ADU plans, a system that sounds like a shortcut but comes with some important nuances.
If you’re considering a detached ADU in the Bay Area or elsewhere in California, this article will:
- Explain what pre-approved ADU plans really are, how they fit into the permitting process, and where they fall short.
- Illustrate why pairing these plans with the right builder, like Apex Homes matters just as much as the plan you choose.
What Are Pre-Approved ADU Plans?
A pre-approved ADU plan is a set of architectural and structural drawings that has been reviewed ahead of time by a city or county building department for compliance with building codes and basic standards.
These plan sets typically include the core ADU design elements that meet local and state requirements. These elements include:
- floor plan layouts
- floor elevations and
- roof plans
Here is the basic idea behind the pre-approval: instead of submitting a completely custom plan and waiting for a lengthy review, homeowners can select a pre-approved plan that has passed many standard reviews.
This can reduce the time spent in the permitting process and help predict review outcomes more reliably than a fully custom design.
Notably, it’s equally critical to understand what these plans don’t provide.
A pre-approved plan does not constitute a complete set for permit issuance on its own. In almost all cases, you’ll still need property-specific submittals like a site plan, energy calculations, and utility or solar documentation required by your city or county. Without these additions, the plan can’t be submitted for a building permit.
AB 1332: California’s 2025 Pre-Approved Plan Mandate
In 2023, the California legislature passed Assembly Bill 1332, a statewide law requiring all local agencies to establish programs for pre-approval of ADU plans. This law went into effect on January 1, 2025, and applies to cities and counties of all sizes, including charter cities.
Under AB 1332:
- Cities and counties must allow ADU plans to be submitted for pre-approval by any qualified designer, builder, or applicant.
- Once approved, jurisdictions are required to publish pre-approved ADU plans online and identify the architect, engineer, or firm that created them.
- If a homeowner submits a complete building permit application for a detached ADU using a pre-approved plan, the agency must approve or deny the permit within 30 calendar days.
- Pre-approved plans may be developed by local agencies or private design professionals, and cities are not required to own the plans or offer them for free.
In practice, that means more options for homeowners, but also more variation in plan quality and price, since not all plans are created equal.
For instance, some pre-approved plans meet basic building codes but use state-generic designs They’re often not optimized for California soil, Bay area seismic standards, or efficient construction sequencing.
That’s why partnering with a builder who understands both permitting and field conditions can save time and avoid expensive missteps.
Two Types of Pre-Approved Plans: Understanding Your Options
When evaluating pre-approved plans in California, you’ll generally encounter two broad categories:
City-Designed Plans
Some municipalities have their own pre-approved plan sets or curate a library of basic designs. These are often:
- Created by municipal staff, hired architects, or consultants
- Designed to comply strictly with local zoning and building code
- Offered to property owners at no cost or very low cost
City-designed plans offer immediate availability with no licensing fees, and they help speed up plan review since core compliance is already checked.
These plans, however, also have limitations because they use basic, generic designs that may lack value engineering or material quality considerations. They also have limited support if you want customization beyond the basics.
For example, in Santa Clara City, homeowners can buy pre-approved ADU plans created by licensed designers or builders and combine them with property-specific site and energy documents to submit for a building permit.
Modifications beyond simple adjustments may disqualify the plan’s expedited status and require additional review or licensed professional stamps.
Designer/Builder-Submitted Plans
Another approach under AB 1332 is for architects or design‑build firms to submit their own plan sets for pre‑approval. These plans:
- Are created by licensed architects or experienced ADU builders
- Are reviewed and pre‑approved by the city or county
- Remain owned by the designer or firm (not the city)
Designer/builder-submitted plans:
- Are better tailored to real-world construction and optimization
- Involve designers who often provide support throughout permitting and construction.
- Typically reflects quality materials and Bay Area conditions.
It is important to consider that these plans may involve licensing or purchasing fees. Its availability also depends on which designers have submitted plans.
Apex Homes’ pre‑designed ADU plans fall into this category. These plans are crafted with both permitting efficiency and construction quality in mind — combining streamlined code compliance with smart value engineering that helps shorten timelines and avoid costly surprises.
Pro tip: Schedule an Apex Homes consultation now to review plan options and see how we can tailor our designs for your property.
Which California Cities Offer Pre-Approved Plans?
Pre‑approved ADU plan programs are spreading rapidly across California in response to AB 1332. Here’s a look at what’s available, especially in the Bay Area:
Bay Area Programs
- Santa Clara City offers vendor-submitted pre-approved ADU plans reviewed for building, energy, and zoning compliance. Homeowners purchase plans and submit site-specific documents for faster permit issuance.
- The city of San Jose maintains a pre-approved ADU vendor list, where homeowners can contact local builders/designers whose plans have already been pre-approved by the city. These plans include a range of foundation‑only or full ADU options.
- Milpitas provides standard construction sets for detached ADUs that meet city code, available for use if the site qualifies and the plan is not modified beyond pre‑approval criteria.
- Concord city offers a free pre‑approved ADU plans library with multiple plan choices that require only site plan and zoning compliance submittal to move toward a building permit.
- Newark city is building its own pre‑approved ADU plan gallery under AB 1332, where homeowners will soon be able to select from city‑approved designs for their projects.
These programs reduce uncertainty and can accelerate permit issuance, but they still require compliance with local setback, utility, and site‑specific requirements — which is where a builder like Apex Homes steps in to guide the process.
What If Your City Doesn’t Have a Program?
Not every California city has launched a pre-approved ADU program yet, especially in unincorporated areas. Even so, homeowners can still build efficiently using pre-designed ADU plans that align with statewide building codes and local zoning requirements.
Apex Homes’ pre-designed ADU plans are built to work across California jurisdictions, whether or not a city offers its own approved plan library. This design-build approach gives homeowners the efficiency of pre-approved plans while ensuring proper support through permit issuance, construction, and inspections.
The result is a streamlined approval process with fewer redesigns and greater flexibility in materials, finishes, and layout than most generic city plans allow.
Key Benefits of Pre-Approved Plans
While pre-approved plans are not a one-size-fits-all solution, they offer several notable advantages for homeowners, especially in California’s high-demand housing market.
Faster Permits
Because the plans are already reviewed for code compliance, cities can often process permits more quickly, reducing delays in the approval process.
Reduced Costs
Pre-approved plans limit redesigns and repeated plan checks, helping homeowners save on design fees and avoid costly construction delays.
Code Compliant
These plans meet state and local building code requirements, lowering the risk of unexpected changes during plan review or construction.
Simplified Process
With fewer revisions and clearer submittal requirements, pre-approved plans make it easier for homeowners to move from design to permit issuance with confidence.
Build Smarter with Pre-Approved ADU Plans and the Right Builder
Pre-approved ADU plans can speed up the permitting process, but they’re only one part of a successful project.
The right builder ensures those plans translate into a high-quality, code-compliant ADU that fits your property and budget. Apex Homes combines pre-designed ADU plans with experienced design-build support to help homeowners move from approval to construction with confidence.
Get a free estimate with Apex Homes today to explore the best ADU plan for your property.
FAQs
What are pre-approved ADU plans?
Pre-approved ADU plans are architectural and structural designs reviewed in advance by a city or county for code compliance. They help streamline the permitting process but still require site-specific documents before permit issuance.
Are pre-approved ADU plans free in California?
Some cities offer free or low-cost pre-approved ADU plans, while others approve plans submitted by designers or builders that may include licensing or usage fees.
Can I modify pre-approved ADU plans?
Yes, minor changes are usually allowed, but major design modifications may trigger additional plan review, fees, and longer approval timelines.
Which California cities have pre-approved ADU plans?
Many cities now offer programs, including Santa Clara County, San Jose, Milpitas, and Concord. More cities are adding plans to comply with California’s AB 1332 requirements.
What is AB 1332 and how does it affect ADU plans?
AB 1332 requires all California cities and counties to offer pre-approved ADU plans starting in 2025, helping standardize approvals and reduce permitting delays statewide.