ADU Pre-approval Plans: Is It Right for You?

Without a doubt, the construction of ADUs has accelerated rapidly over the past few years.

State laws understand that Accessory Dwelling Units and Junior Accessory Dwelling Units (JADUs) are integral to community development, making permission easier than ever in many counties.

Cities have started to respond to the growing interest in ADUs, seeing the potential for Accessory Dwelling Units to help provide significant affordable housing volume. For example, the March 2021 launch of the Los Angeles ADU Standard Plan Program with its Approved Standard Plans marked another example of cities releasing pre-approved ADU programs in response to consumer demand. Cottage has contributed its own standard ADU building plans to the LA Standard Plan Program to help support the initiative.

But what are ADU pre-approved plans, and how can they help an interested ADU owner build their ADU from start to finish? Is Minix Home involved in these pre-approved ADU programs? We cover all those details in this article.

Interested in a custom, stick-built ADU or one of our pre-approved plans and a no-hassle process? Click the “Get Started” button on the top right-hand corner to get a Free Consultation and Estimate Today.


What are Accessory Dwelling Unit Pre-Approved Plans?

ADU pre-approved plans are ADU designs that have been vetted by city building and/or planning departments for fast-track approval. They can be selected for use by homeowners for their own ADU projects. Removing this barrier will help save you time and money.

However, there is one key caveat. This does not mean that the designs already have their building permits, but that several elements of the permitting process for your ADU will be accelerated upon application submittal by a Minix Home or another ADU designer on your behalf.

Working with construction professionals or a city planner can greatly help with the preparation of your building permit submittal, so you can know beyond a shadow of a doubt that you’ve considered everything on your local building department’s ADU universal checklist.

City-Owned Versus Designer-Owned ADU Pre-Approval Programs: What’s the Difference?

Pre-approved ADU programs typically fall into two categories: city-owned plan programs and designer-owned plan programs.

In the first type of program, cities contract with a design or architecture firm to create a set of ADU plans that the city will pre-approve according to their regulations and code requirements. In these programs, the municipality will typically own the plans once they are designed.

Property owners can then access these plans for free on the city website but will need to find additional planners elsewhere, such as site surveyors, energy consultants, and even additional designers, to tailor the plan set to a specific primary dwelling unit. Danville, CA is one example of a city that has a city-owned plan program.

In the second type of program (designer-owned plan programs), cities will publicize an open or ongoing call for architecture and design firms to submit ADU plans for pre-approval and then list the pre-approved plans on their website for homeowners to peruse.

In these programs, the original designer maintains ownership of the pre-approved plans. Community members can then reach out to the designer of the plan they select and work with the designer throughout the process of building their ADU. Los Angeles’ program is one example of a designer-owned plan program.

In both types of programs, pre-approved plans can cut down the time it takes to permit your ADU by over a month, if not more. Another bonus is that many pre-approved ADU programs also allow for pre-approval of basic structural and Title 24 calculations, which can further cut down on the time it takes to get your ADU to construction and provide significant savings.

ADU pre-approved plans cost savings: Real or not?

Pre-approved designs have the potential to save homeowners thousands of dollars. Because permitting a pre-approved design saves planning and/or building department staff time, some cities with pre-approval programs, like Fremont, CA, can offer significantly lower fees for pre-approved ADU designs.

Pre-approved designs also save design and architecture firms staff time, so selecting a pre-approved design can also lower costs for designing your ADU. In addition, Cottage’s pre-approved ADU plans are always cost-optimized and construction-ready, saving you both time and money. That is not the case for all pre-approved plans—many are designed as urban utopias with unrealistic designs and features that are not an effective use of your space or budget.


Most pre-approved ADU programs enable designers to offer several pre-approved options, but if your ideal ADU is small and efficient, going the custom route using an A-to-Z ADU provider like Cottage may still be cheaper. There will always be opportunities to save costs, however, on things like finishes, as these choices are separate from the pre-approved plan programs.

If I Use a Pre-Approved ADU Plan, Do I Still Need an Architect?

The short answer is that it depends. If you use a plan set from a city-owned pre-approval program and have no changes or very minimal ones for your plan set, you may be able to move forward without an architect. However, most allowed modifications to pre-approved plans will still likely require an architect. Usually, most homeowners will have a designer assist on the site-specific pages of the permitting plan set.

With designer-owned plan programs, you are required to work with the original designer/architect. Because the designer owns their pre-approved design, working with them on small modifications to your plan is a seamless process. ADU companies like Cottage offer assistance through the entire process for a flat fee, so we can assist you from the minute you reach out about a pre-approved plan all the way through construction.

What Changes Can I Make to a Pre-Approved ADU Plan?

Most, but not all, cities with pre-approved plans allow homeowners to make small changes to pre-approved designs. For example, San Jose’s pre-approval program allows for moving one load-bearing wall or beam and up to 25 percent of non-structural changes to the preferred ADU design.

These customizable options can mean including large windows, changing the exterior materials, or making other tweaks that can make your ADU or JADU feel like home. It cannot, however, add square footage for a home office or dining area that wasn’t present on the original plan. If a large living room or wrap-around patio is integral to your ADU dreams, these should be present in your original pre-approved plan.

When it comes to maintaining pre-approval status while still making small modifications, the benefits of designer-owned plan programs stand out. Working with the designer who owns the plans makes it seamless to quickly draft these variations and submit your plans to the city.

In contrast, working with city-owned pre-approved plans might require going back to the original architect to make modifications or finding an entirely new architect or designer. Minix Home can offer homeowners both the ability to make custom modifications and an efficient design and permitting experience all in one no-hassle process.

It’s important to note that regardless of what pre-approved plan you choose, these pre-approved plans still must go through the normal site-specific checks in order for the project to receive a permit. For example, any necessary consultations with arborists or site surveyors would still apply.

Fortunately, ADU experts like Minix Home full team of homeowner consultants can walk you through any unexpected site conditions and get you on your way to receive your permit for your pre-approved plan.

Which cities have pre-approved ADU plans?

CA Cities with Pre-Approved ADU Programs (non-exhaustive):

San Jose

Los Angeles




Should I use a pre-approved ADU plan for my project?

In our experience, pre-approved ADUs can have their pros and cons. A well-designed pre-approved ADU plan can save your project time, money, and future headache, while a poorly or inefficiently designed ADU floor plan can eat away at any time or cost savings you thought you might have.

Regardless of your final decision for your ADU project, it is important to get as many expert opinions as possible. Whether you plan to live in your backyard apartment yourself or intend to use your accessory structures as a rental unit, you want to ensure that your ADU is comfortable and functional for your needs. Our Cottage design team has seen a wide range of ADU designs and can help you make an informed decision of whether to use a pre-approved plan or a different approach.

Contact us today using the link below for a Free, No-obligation Consultation & Estimate for your ADU vision with one of our ADU experts!

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