Garage to ADU Conversions: A Beginners Guide

Garage to ADU Conversions: A Beginners Guide

The American garage is generally regarded as a place where cars rarely reside and where half-attempted dreams and aspirations permanently stay.

This is not always the case, however. For example, global corporations like Amazon and Apple both started in a garage long ago.

Still, most homeowners usually convert their garage into an ADU or an "accessory dwelling unit.

An accessory dwelling unit 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.

A garage to ADU conversion may be undertaken to expand a residential property, house a relative, or start a small business.

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 a garage to ADU conversion 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.  

Homeowners' association members may need prior approval before initiating a garage to ADU conversion.

And 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. 

Do you need help with a garage to ADU conversion? Contact My Site Plan today.

Related - How to Convert a Garage into a Master Bedroom

Garage conversions to accessory dwelling units have been around for a long time, and they're only increasing in popularity. When considering a garage conversion, many people think it will be a simple, clear-cut slam dunk. For some, it may be that, but for most property owners, there are significant considerations to weigh.

Garage to accessory dwelling unit (ADU) conversions are the second most common ADU conversion next to basement ADUs. Read on to see if a garage conversion is right for you.

Key Points:

  • What are Garage Conversion ADUs?
  • What is involved in conversion?
  • Is conversion right for me?
  • What is the cost of a garage to ADU conversion?

  • What Exactly Are Garage Conversion ADUs?

    ADUs are also known as mother-in-law cabins, cottages, carriage houses, and by many other names. They can be attached, detached, close to the primary home, or further back on the property.

    Garage to ADU conversions are can be attached or detached, and they're remodeled from existing sheds and garages. State regulations guide an accessory dwelling unit's dimensions and structural designs. 

    There are accessory dwelling units that are positioned above or attached to a garage. Conversions are when the preexisting garage or a portion of it is converted into an ADU.

    Related: How to Get a Permit for an In-Law Unit 

     A grey colored garage to ADU structure.

    Why Convert to a Garage 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. Taking advantage of preexisting housing stock provides several benefits. Take a look at just a few:

    • Your garage may already have a cozy charm to it, and it may already fit in with the neighborhood.
    • You can save on excavation and construction costs because your ADU's outer shell will already be built.
    • 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.
    • You may already have water and power lines ran to the ADU, and you might even already have a sink or overhead lights!
    • 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.
    • 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.
    • Since the garage is a preexisting structure, you won't have to give up any additional space from your yard by converting it to an ADU.
    • Garage converted ADUs can add density discreetly to the neighborhood in a way that might not be noticeable by passersby!

    Are you looking for residential and commercial site plans for permits? Contact My Site Plan today!

    interior wooden part of the home

    Garage to ADU Conversions Top 5 Dealbreakers

    Hidden costs can be everywhere with a project like this. It's best to analyze the situation before beginning any construction.

    Here are four common deal breakers for ADU garage conversions:

    1 - 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.

    2 - Structural Challenges

    Sometimes, a garage may be in such disrepair that it can't handle the conversion because its, 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.

    3 - Remnants of the Past

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

    4 - 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.

    Related: How to Build the Perfect In-Law Unit 

    Can I Convert my Garage?

    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. 

    My Site Plan is a veteran-owned business that offers 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 and execute your plans within 24 hours. Take the guesswork out of the process and allow My Site Plan professionals to help you from here.

    Interior shot of a two-level garage to ADU conversion.

    The Cost of Conversion

    Since each conversion requires different types and amounts of work, it's tough to offer a cost range. Between permitting, architecture, and contractor costs, garage ADU conversion can easily reach the $80,000-$150,000 range. If there's barely anything to do besides getting permitted, costs will be less. On the other hand, if you live in an expensive city or run into any red flags involved with the property’s structure, things might get even pricier.

    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.

    Related: 10 Best Backyard Workspaces


    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. When done with ample premeditated planning, converting your garage to an ADU can be an exhilarating experience.

    Are you looking for residential and commercial site plans for permits? Contact My Site Plan today!

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    • Annie Rosellini