THIS IS NOT A SURVEY, NOR IS IT INTENDED TO BE OR REPLACE ONE

A Beginner’s Guide To Garage ADUs

RSS
A Beginner’s Guide To Garage ADUs

The American garage is generally regarded as a place where cars rarely reside and where half-attempted dreams and aspirations permanently stay (unless you’re talking about Amazon and Apple, both of which were born in garages). That’s why converting a garage into an Accessory Dwelling Unit (ADU) can be a lucrative option.


According to a recent National Home Association of Builders study, over 1.4 million American properties in the United States have at least one garage to ADU conversion on it. If you’re thinking of going ahead with a garage ADU, here’s everything you need to know. 

What is an accessory dwelling unit?

An Accessory Dwelling Unit (ADU) is a secondary residential unit on the same lot as a primary home. ADUs are also known as mother-in-law cabins, cottages, carriage houses, and by many other names. They can be attached, detached, basement conversions, attic conversions, garage conversions, close to the primary home, or further back on the property.


State regulations guide an accessory dwelling unit's dimensions and structural designs, but they can have their own kitchen, bathroom, and living areas. ADUs provide affordable housing, generate rental income, support multi-generational living, and increase property value. 

What is an ADU garage conversion?

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.

ADU garage conversion

Can I convert my garage into an ADU?

Converting your garage into an accessory dwelling unit can be one of the simplest and most economical ways to create an additional dwelling on the property.

Reasons to do an ADU garage conversion

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!

Reasons against converting your garage to an ADU

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…

How much does it cost to convert a garage to ADU?

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.

How to convert garage to ADU

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. 

ADU garage conversion tips

If converting your garage into an ADU sounds like the right choice for you, it'd be wise to consider having a contingency budget in place for any unforeseen cost possibilities. It'll also be worth the time and money to have an ADU professional analyze your property.


Most importantly, make sure to have My Site Plan draw your plans and work out the details with you before beginning any construction. We offer non-certified plans, just like the ones needed to convert a garage to an ADU. They will help decide what amount of detail your project requires. Take the guesswork out of the process and allow My Site Plan professionals to help you from here. When done with ample premeditated planning, an ADU garage conversion can be an exhilarating experience.

Garage ADU FAQs

What are the common legal requirements for converting a garage into an ADU?

Legal requirements can vary by location but generally include obtaining building permits, ensuring the structure meets zoning laws, adhering to building codes, and sometimes obtaining approval from homeowners' associations.

How long does a garage to ADU conversion typically take from start to finish?

The timeline for a garage to ADU conversion can range from a few months to over a year, depending on the complexity of the project, local regulations, and the efficiency of contractors and permit processing.

Can converting a garage into an ADU increase property taxes?

Yes, converting a garage into an ADU can increase property taxes as it typically increases the property's value. The exact impact on taxes can vary depending on local tax laws and the extent of the renovations.

Are there financing options available specifically for garage to ADU conversions?

Yes, some financial institutions offer specific loans for ADU construction, including home equity loans, personal loans, or renovation-specific financing options. It's advisable to consult with financial experts or lenders who specialize in home renovations.

What are the environmental impacts of converting a garage into an ADU?

Converting a garage into an ADU generally has a lower environmental impact compared to new construction, as it utilizes existing structures and materials. However, the impact can vary based on the materials used and the efficiency of the new dwelling.

How does the presence of an ADU affect resale value?

The addition of an ADU can significantly increase the resale value of a property by adding a potential income source or appealing to buyers looking for multi-generational living options. The exact impact can vary based on the market and the quality of the conversion.

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.

Previous Post Next Post

  • Ryan Crownholm