From 2017 to 2019, the City of San Diego saw nearly a 300% increase in the number of ADU applications submitted to the building department.
And that number is only getting higher.
If you are thinking of building an ADU on your property, you are not alone.

Source: San Diego Development Services
The first step to building an ADU is to ensure that your property eligible for an ADU, or as I like to call it: ADU-able. If you’re looking to buy an ADU-able property, get in touch with me. I’ll help you find the properties with the most ADU potential available on the market today.
There are three main phases to building an ADU:
- Design
- Permits
- Construction
Obviously, any major construction project requires advanced planning and due diligence. Therefore, the goal of this guide is to walk through the main phases of building an ADU and to cover the most important factors to consider. My hope is that by the end of this guide, you will feel more knowledgeable about tackling your ADU project and will feel more confident about getting started. Ready? Let’s go.

Phase 1) Design Your ADU
As mentioned in our ultimate ADU guide, it is critical to work with a designer who has experience with ADUs. Not only will they understand how to design for small spaces, but they will be knowledgeable about the ADU laws affecting your area. This is important because ADU laws can differ from city to city, so it’s essential to work with a designer who is familiar with latest laws and regulations to ensure that your ADU project will run smoothly and efficiently.
The design of your ADU will depend entirely on your goals. Evaluate your goals to help inform the size, amenities, and features you want your ADU to have. Here are a few of the most common reasons why homeowners build ADUs.
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Rental
As a rental, you’ll probably want to take the most cost-effective route. However, you’ll also want to make sure that your unit is designed in a way that can get you the best rent for your area. For example, a one bedroom unit will typically rent higher than a large studio. Your ADU-experienced designer will be able to provide you with a design that maximizes the amount of available space you have.
Additionally, there are certain amenities that tenants love, including:
- In-unit washer/dryer
- Natural Light/windows
- Updated fixtures
- Outdoor space
- Storage and closet space
- Laminate wood floors
- Parking
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Aging family members
One of the main reasons why homeowners are turning to ADUs is to provide a solution for their aging parents. With the rising costs of nursing homes and assisted living facilities, ADUs can be a more cost-effective and safe way to keep your loved ones closeby. By keeping elderly parents nearby, you’ll be able to provide them with the care they need while still maintaining their independence.When designing a unit for senior family members, you may want to consider universal design.
What is universal design?
Universal design includes design elements that increase accessibility to all people regardless of disability or age. Universal design elements may include:
- Doorways that are wide enough for a wheelchair
- Wide bathrooms that allow a wheelchair to make a full turn
- Ensuring there are no thresholds or levels on the floor or entryways By incorporating universal design into your unit, you will help ensure that your parent or loved one will be as safe as possible. Therefore, when choosing a designer, it’s important to choose someone who has experience building accessible spaces and is able to point out certain elements in the design that you may have not thought about yourself.
Guest house for yourself, friends or family
ADUs are a great way to house guests who are visiting. But did you know that more and more homeowners are creating ADUs for themselves to live in? This is particularly common with empty-nesters. Their adult children are out of the house, and they don’t want to deal with the maintenance of living in a large home. By moving into the ADU, they’re able to rent out their primary home for maximum rental income.
When designing an ADU for yourself or for friends and family to stay in, the approach will be a lot different from designing the unit as if it were a rental. Evaluate what you want the most out of a smaller living space, and make it yours.
You want the unit to be as comfortable as possible and if you can afford to splurge on the things that are important to you such as: noise-reducing windows, or the nice granite countertop you’ve been eyeing on Pinterest — go for it! Now that you’re designing a smaller space, you might be able to afford the dream kitchen you’ve always wanted but couldn’t afford in your much larger home.
We’ve covered a few high-level design concepts to help you visualize your dream ADU. Your designer will work with you on achieving your goals, and should be communicative and collaborative throughout the process. Once your designs are completed, it’s time for the next phase: submitting for permits.
Phase 2) Permit Processing
Once you have a full set of plans, it’s time to submit them to the city building department for building permits. Permit processing is easily one of the most daunting tasks in any construction project, let alone building an ADU.
City building departments aren’t always the easiest to get a hold of, and unless you’re a professional designer or architect, it may be difficult to understand the ADU rules and regulations to abide by in terms of the design.
Therefore, it’s ideal to work with a designer that will go through the permit processing with you. Not only will they be able to work efficiently in implementing feedback from the city, but a good firm will likely have connections with your city building department to get you your permits as cost-effectively as possible.
In the past, submitting for permits was a huge bottleneck with homeowners waiting as long as 6 months just to receive an answer.
Things have changed.
As of 2020, California state law mandated that local jurisdictions must act on ADU applications within 60 days. Although this doesn’t mean that your ADU will get approved right away, it means that the city is reviewing your plans and must keep things moving.
There are also a number of fees that you’ll need to cover, depending on the city you’re located in. These fees include, but aren’t limited to:
- School Fees
- Water/Sewage Fees
- Plan Check Fees
- Development Impact Fees (varies by municipality)
Depending on the scope of your project, you can expect to pay at least a couple thousand dollars in permit fees. The good news is that as of 2020, state law has mandated that all ADU units under 750 sq ft are exempt from Development Impact Fees. In San Diego, this is an automatic savings of an estimated $15K!

Phase 3) Build Your ADU
After your plans have been approved by the city building department and you have permits in hand, it’s time to build your ADU. If you’re hiring a general contractor to build the unit for you, it is critical that you do your due diligence when selecting the right person for the job. Again, you’ll want to work with someone who has experience building ADUs to help ensure that your project will go smoothly.
Your ADU will not be completed overnight. You can expect the build to take about 3-6 months. This means months of having an active construction site in your backyard or home, and a team of plumbers, electricians, carpenters, and other construction teams in and out of your property. Therefore, it’s essential to work with a general contractor who is experienced, knowledgeable, honest and most importantly, communicative throughout the entire build.
Once you’ve received your building permits, it’s time to start construction. Again, it’s important to find a contractor with ADU experience. Since building an ADU can take 3-6 months, you’ll want to work with a team who is experienced, honest, knowledgeable, and communicative throughout the process.
After months of hard work and dedication, congratulations! You can finally enjoy your ADU. As you can see, building an ADU is a long process that isn’t easy. Building an ADU is certainly a big investment. But if you make the right decisions by investing in the right teams to work with, you will be saving yourself from a lot of headache and stress in the long run.
Are you looking for an ADU-able property to build your own ADU? Find out how to identify ADU potential with my quick guide or contact me to get started on your property search.
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