A Beginner’s Guide To Garage ADUs

An ADU garage conversion is basically a garage that has been converted into an additional dwelling on a residential property. So, instead of housing a car, the garage is converted into a home office, bungalow, mini-apartment, tool shed, or some other mini-dwelling function.

Garage to ADU conversions can be attached or detached and they're remodeled from existing sheds and garages. Some ADUs are positioned above or attached to a garage. However, an ADU garage conversion turns a pre-existing garage (or a portion of it) into an ADU.

Garage to accessory dwelling unit conversions are the second most common ADU conversion next to basement ADUs. They may be undertaken to expand a residential property, house a relative, or start a small business.

Taking advantage of pre-existing housing stock provides several benefits. Take a look at just a few:

• Save on excavation costs: You can save on excavation and construction costs because your ADU's outer shell is already built. And, since the garage is a pre-existing structure, you won't have to give up any additional space from your yard by converting it to an ADU.

• Match your existing home perfectly: The materials used for older structures may not be produced anymore, leaving your new ADU with a unique outer shell, unlike any other, while still matching your primary home.

• Use existing utilities: You may already have water and power lines that run to the ADU, and you might even already have a sink or overhead lights! Plus, if your garage is attached to the primary residence, the newly converted ADU will offer easy access between the two buildings should the need ever arise.

• Make your unofficial ADU official: Your garage may already have a cozy charm to it and it may already fit in with the neighborhood. In fact, you may already be using your garage as an unofficial ADU. Maybe you're using it as a man cave, she shed, or spare bedroom. All you'll need to do is bring it up to code and get permitted.

• Increase housing: ADUs made from garage conversions offer housing in neighborhoods that would otherwise be full to the brim. This can be a benefit to the property owner and the tenant/family living in the ADU alike. It may allow the owner and the tenant to live in a neighborhood that neither would otherwise be able to afford. Plus, garage converted ADUs can add density discreetly to the neighborhood in a way that might not be noticeable by passersby!

For some, converting their garage to an ADU is a no-brainer. But there are reasons not to go through with it too. Here are four common deal breakers for ADU garage conversions:

• Shared utilities: Once you begin investigating your property, it may come to light that you and your neighbor share a sewer line. If this is the case, you'll be looking at a considerable upgrade to your system.

• Structural challenges: Sometimes, a garage may be in such disrepair that it can't handle the conversion because it’s, well, falling apart. Other issues that commonly arise are when the ADU beams are too weak to support the intended second story, or the ADU is sitting at a level that will be susceptible to flooding.

• Asbestos: "Remnants of the Past" is a fancy way to say that you might find asbestos! Check closely.

• Energy challenges: Some garage walls may be too thin to add layers to bring it up to code. In this case, it's necessary to fur out the walls.

Hidden costs can be everywhere with a project like this. It's best to analyze the situation before beginning any construction. Which brings us to our next point…

It could cost you as much as $20,000 to $400,000 for you to initiate a garage to ADU conversion on your residential property. How much you ultimately pay for an ADU garage depends on your construction intent.

Are you converting a basement portion of your garage into an ADU or just the garage itself? Or are you converting your garage into an ADU and adding additional space as well? Such considerations like work hours, design costs, and materials cost will add to the final garage to ADU conversion construction costs. Additionally, you may have to consider neighbor land boundary lines, permits, and fines, and the cost of adding extra utilities.

Ultimately, it's best to get quotes and estimates to answer the "how much" questions because so much will depend on the specific property details and your location.

Converting a garage comes down to one thing: following rules. As long as you carefully follow your local laws and regulations, you should be able to convert your garage. There are quite a hefty number of rules to understand and remember, so it is wise to seek professional help on your journey.

Success with this project hinges on the very beginning of the process: the plans. Whether you're converting a one-story garage or adding another level or horizontal addition, having reliable site plans created by expert CAD designers will ensure the project's ultimate success.

Take a look at these ADU regulations for Los Angeles to get an idea of what you’ll be looking for. 

This post was originally published on 2020-08-28 by Annie Rosellina. It was updated on 2024-06-05 by Ryan Crownholm to reflect the most recent data.