Garage Conversion ADUs

Everything you need to know about Garage Conversion ADUs including how to decide if a garage conversion is right for you, the steps you'll need to take to make it happen, and common challenges.

Are you looking for a way to add more living space to your home without the hassle and expense of a full-scale addition? If so, a garage conversion Accessory Dwelling Unit (ADU) might be the perfect solution for you. In this article, we'll explore the benefits of converting your garage into an ADU, how to decide if a garage conversion ADU is right for you, and the steps you'll need to take to make it happen. We'll also look at some case studies of successful garage conversion ADUs and provide tips for overcoming common challenges and navigating local zoning and building codes.

Otto ADU has completed dozens of garage conversions and are happy to share our expertise on their design, permitting, and construction. We’ve put together the internet’s most comprehensive guide on the topic to further our mission of helping homeowners make the most of their property and fight the housing crisis.

Table of Contents

Benefits of converting a garage into an ADU

Garage to Accessory Dwelling Unit conversions are the most popular type of ADU built in California and offer some unique benefits over ground up and prefab ADUs.

Garage Conversion ADUs are generally more affordable than prefabricated and ground up ADU options, as they can utilize existing structures, saving on construction costs while delivering the same or higher quality construction. Many cities have more relaxed planning requirements, express permitting, and lower fees for ADUs that are converted from existing space. Moreover, the total project timeline is often faster than prefab or modular, as there are no factory wait times.

Another great benefit of garage conversion ADUs is their efficient use of space on your lot. Whether detached or attached, you will never have to worry about your city's setback requirements when converting existing space. This means that you can retain more of your yard space than if you were to build another type of ADU.

How to decide whether a garage conversion ADU is right for you

Before you decide to convert your garage into an ADU, there are a few key considerations to keep in mind. First, you'll need to determine the size of your garage and whether it's big enough to accommodate an ADU. In general, you'll need at least 360 square feet of space to build an ADU — usually, that’s an 18 foot by 20 foot 2-car garage. Smaller spaces are possible, but will likely require creative planning and space saving solutions such as murphy beds. You'll also need to consider the layout of your garage and whether it would be feasible to convert it into living space. Access and privacy are the two biggest considerations in ADU space design.

Another exciting benefit of a garage conversion is that you can often utilize existing structural framing, foundation, and exterior cladding. However, it is important to have your existing space inspected by an experienced contractor to determine the extent of what you can keep. Learn more in the “challenges and considerations” section below.

You’ll also need to consider how you’re using your existing garage and how to accommodate those uses in the future. Of the hundreds of garages we have assessed for ADU feasibility, surprisingly few have been used to store cars! Most commonly, garages are used for infrequently accessed storage. Many homeowners take this project as an opportunity to reassess why they are holding onto items they no longer use. Many of our clients have decided to pare back their storage to essentials and move it into a new storage shed, or include ample storage in the ADU.

Types of garage conversion ADUs

There are several different types of garage conversion ADUs that you can consider. These include:

Detached ADUs

Detached ADUs are standalone structures that are separate from the main residence. They can be built in the backyard or on a separate lot and are typically used as rental units or guest houses. In Los Angeles, neighborhoods developed between the 1920’s and 1960’s commonly feature detached garages in the rear yard. These make perfect second units that can have independent access and their own private outdoor space. Detached ADUs can easily be enlarged by constructing a new addition at the same time as you convert the garage.

Attached ADUs

Attached ADUs are built as an extension of the main residence and share a common wall with the main home. They can be accessed through a separate entrance and/or through the main residence. As attached garages were not commonly built until the 1960’s, they are often in good structural condition.

Junior ADUs

Junior ADUs (JADUs) are a newer type of ADU that was legalized in 2020. These units must be constructed within existing residential space or an attached garage. These units may include a connection to the main house, making them ideal for use as an extension of the living space. If there is a direct connection to the main house, JADUs do not need their own bathroom. Junior ADUs have distinct requirements from ADUs so it is important to talk to an experienced designer before deciding whether it is right for you.

Layout and Design

The layout of your garage conversion ADU will depend on a variety of factors, including the size of your garage and your intended use for the space. Unlike pre-approved plans or prefabricated units, garage conversions work within existing space constraints and every design is unique! This means that the layout and design are one-of-a-kind and can be tailored exactly to suit your needs. Having designed hundreds of garage conversion ADUs, Otto ADU incorporates best practices into our unique design process.

Design requirements

According to state law, every ADU must include a full bathroom, small kitchen, and independent access. Although space is always a priority in ADU design, Otto ADU highly recommends not skimping on the bathroom size. A 5’ x 8’ bathroom — as opposed the most compact design — significantly increases the day-to-day comfort of ADU living. Otto ADU has even designed larger bathrooms to accommodate roll-in showers for aging-in-place or freestanding baths without compromising on the overall functionality of the unit.

Intended use & Design Preferences

When designing the layout of your ADU, it's important to consider the needs and preferences of the people who will be using the space. If you're building an ADU to use as a rental unit, for example, then separate access, visual privacy, and a full set of appliances are key. On the other hand, if you're building an ADU to use as a guest house or home office, you might prefer to visually tie it to the main house and provide minimal appliances. This is where the flexibility of garage conversion ADUs really shines. Unlike off-the-shelf prefabricated ADUs, garage conversion ADUs can be designed exactly to match your budget, aesthetic preferences, and the intended use of the space.

Studio vs. 1-bedroom

If you have a larger garage, you may be able to build a one-bedroom ADU with separate areas for living, sleeping, and cooking. Otto ADU typically recommends at least 420 square feet of living space for 1 bedroom units.

If your garage is smaller, you may need to opt for a studio layout with a combined living and sleeping area. This is why it’s important to work with a designer experienced with small spaces. A well thought out studio will feel larger than it is and use layout and screening elements to make a cozy semi-private sleeping area.

Vaulted ceilings

Vaulting the ceiling is a high-impact design decision that can make small a space feel larger. However, vaults and skylights must be coordinated with structural engineers and experienced contractors to ensure they are constructed to code and are long-lasting.

Footprint & Setbacks

Another great benefit of garage conversion ADUs is that they don’t have to comply with your city’s setback requirements. Most garages were built right up against the property lines, which is something that wouldn’t be allowed today — new buildings are required to be setback from property lines anywhere from 4’ to 20’ or more! If you convert your garage into an ADU, you can keep the footprint exactly the same. This means that you can retain more of your yard space than if you build a ground-up or prefabricated ADU. Keep in mind that any extensions beyond the existing footprint will have to be setback 4’ from the property line. In addition, walls that are less than 3’ from the property line cannot have any doors or windows.

Above-the-garage ADU

Building above the garage is a popular request, and for good reason: it allows you to keep your car or storage space without sacrificing valuable yard space for your ADU. However, building above the garage has several important considerations. Namely, it will likely require significant structural modification or even complete rebuilding of the existing garage to support the second story. Second stories must also abide by the same 4’ setbacks for new construction and have additional setback requirements if they are near power lines.

Challenges and Considerations

Converting a garage into an accessory dwelling unit (ADU) is be a complex and nuanced process, and homeowners may face a number of obstacles along the way. The process involves understanding city zoning regulations and the application process, and working with an experienced designer, structural engineer, and energy consultant to determine your unique ADU design. Another challenge that homeowners may face is finding a qualified contractor to handle the conversion work. It's important to find a contractor who has experience with ADUs and can complete the work to the highest standards.

Otto ADU is a one-stop-shop for garage conversion and ground-up ADUs. Unlike many other ADU companies, we work directly on every stage of the process--from design and permitting to construction of ADUs--and have become the foremost expert on ADU garage conversions through hard-won lessons.

Here are a few of the most important things to consider when converting your garage to an ADU:

Existing permits

In order to reap the benefits of converting an existing space into a new ADU, the structure must have been previously permitted. Thankfully, city building departments keep historic building permit records either online or in a physical archive. For example, Los Angeles City keeps some of their records at this link, and LA County requires an individual to visit the County office associated with their property to obtain permit records.

Structural issues

Some garages may have structural issues that need to be addressed before they can be converted into living space. These issues may include foundation problems, roof damage, or other issues that can be costly to repair. For example, in LA City, your foundation needs to extend at least 12” below ground — if it doesn’t, it must be underpinned or rebuilt to extend anywhere from 12” to 24” below ground. To avoid unexpected expenses during construction, it is important to have your garage inspected by a qualified builder.

Demolish and rebuild

Rebuilding is possible and sometimes preferred; if large structural repairs are necessary, it may be cheaper and more efficient to completely rebuild. Thankfully cities will allow you to keep the existing footprint and avoid setbacks even if you need to substantially rebuild.

Read this blog post to learn more on the subject.

Limited space

If your garage fits fewer than two cars, you may face challenges in trying to fit all your requirements into the space. Otto ADU has designed amazingly functional ADUs in garages as small as 245 square feet; however, it requires space-saving solutions like murphy beds and may not be enough space for your specific needs. Thankfully, adding an extension or constructing a ground-up ADU in its place may still be a viable option for you.

Budget constraints

While it is the most economical way to build an ADU, converting a garage can still be expensive, especially if you need to make significant changes to the structure. It's imperative to have a budget in place and to be realistic about what you can afford. It’s also important to work with a thoughtful and reputable builder who will do their due diligence and provide accurate costs upfront.

To overcome these challenges, it's critical to do your research, seek the advice of professionals, and be prepared for the possibility of unexpected challenges. By tackling these challenges head-on and being proactive in finding solutions, you can successfully convert your garage into an ADU. Check out our article on How Much does an ADU Cost for more information.

Replacement Storage Solutions

One of the most frequent questions we get asked is “What am I going to do with all my stuff?” When converting a garage into an accessory dwelling unit (ADU), storage is one of the most important considerations.

While we love clean design, minimalism isn’t for everyone and it's important to think about how you will store your belongings and make the most of the available space. One way to do this is by utilizing creative storage solutions, such as built-in shelving, cabinets, and closets within the new ADU. You should also consider smaller appliances (such as 24” wide washer/dryers, 24” wide oven ranges, cooktops, and 18” wide dishwashers), which save space and are more than enough for most ADU uses.

In addition, consider adding a new storage shed for yard tools, bikes, and holiday decorations. There are several custom storage shed companies, and units under 120 square feet do not need to go through the city permitting process.

Design Tips

In addition to storage solutions, there are also a number of design tips that you can use to make your ADU feel more welcoming and comfortable. For example, you can use a neutral color palette to create a cohesive look and make the space feel more open and airy. Otto ADU recommends a lighter paint colors over strong pigments to make the space feel larger and better reflect natural light. Using clerestory windows, vaulted ceilings, and skylights are all great ways to maximize light while retaining privacy.

In small spaces, cohesion of the material palate is key. Err on the side of neutral and wood tones for maximum flexibility and to avoid color fatigue. This color palate can go either modern or classic depending on the fixtures and details. In a small space, it is easier to add color pops through plants and artwork than to repaint the walls or swap out the cabinets.

By following these tips and utilizing innovative storage solutions, you can make your ADU a comfortable and stylish place to live or work.

Local Zoning Code

When converting a garage into an accessory dwelling unit (ADU), it's important to be aware of the local zoning and building codes that apply to your project. These codes are in place to ensure that your ADU is safe, structurally sound, and complies with the requirements of your local jurisdiction. California passed regulations in 2018 and 2020 to streamline the building of ADUs across the state; however, all ADUs must be approved at the local level and abide by local zoning codes.

To determine the local zoning and building codes that apply to your ADU, you'll need to contact your local planning and building department. They will be able to provide you with information about the specific requirements that apply to your project, such as setbacks, size limits, height limits, and parking requirements.

Understanding Historic Requirements

If your project is located within an historic district, you may need special approval from the historic preservation department. If you live in LA City, you can use LA ZIMAS to determine whether you fall within an historic district. Thankfully, a full historic preservation review is not required for ADUs and the building department cannot deny an ADU project on historic grounds alone.

If you do fall within an historic district, your architect may need to meet with the historic preservation department and adjust the design to fit within their material and aesthetic guidelines. These guidelines typically only govern the appearance of the ADU visible from the public right of way. On our projects, we have been asked to add historic window styles and provide fake, non-functioning garage doors to replace the garage’s original.

Understanding Parking Requirements

Accessory Dwelling Units (ADUs) are required to provide an additional off-street parking space, unless the project is located within a half-mile of a public transit stop. City planning guidelines also mandate that single family homes provide 2 parking spaces. However, garage parking that is lost in the construction of an ADU does not need to be replaced. Junior ADUs, which were written as a different state bill, have slightly different requirements and may require replacement parking in some cities. In the rare case that a garage conversion project requires parking, it can usually be achieved with uncovered driveway spots.

Steps for converting a garage into an ADU

Building a garage conversion ADU can be broken down into four stages: planning, design, permitting, and construction. These steps involve either working with individual architects, consultants, and contractors, or going with a full service all-in-one ADU company like Otto ADU.


The planning stage involves defining your goals for the future use of the space and getting rough all-in cost estimates to determine what type of ADU fits your budget and which financing options are best to pursue. Otto ADU recommends contacting the city permitting office for local ADU requirements and getting preliminary estimates from qualified ADU builders.


The design stage involves working with an architect to determine the layout and finishes, and provide an updated budget. Next, a structural engineer and energy consultant prepare the final documentation for the permitting process. It is important not to rush this stage, as many decisions become fixed during the permitting process and can only be changed later with added expense and slowing the project.


Without a full-service ADU company working on their behalf, homeowners must apply to multiple city departments for plan review and approval. During the process, you will also need to communicate city notes and revisions back to the architects and structural engineer to be re-incorporated into the drawings. Without prompt follow-up, many projects spend more time than necessary in this stage. This where it really helps to have a company like Otto to negotiate this process on your behalf!


The final and most important stage of building an ADU is, of course, construction. We strongly recommend working with an experienced ADU contractor during this stage to avoid unnecessary delays. Make sure that you receive thorough contracts that incorporate the complete scopes of work for all items and contingencies. If not, expect expensive change orders later in the process. Finalizing all of the design decisions during the Design phase and pre-ordering building materials (particularly those with long lead times) are key to avoiding lost time during this phase.

Reach more on our Process Page.

Other Options for Building an ADU

If a garage conversion is not large enough to suit your needs, consider building a ground-up ADU. Ground-up ADUs offer many of the same customization benefits as garage conversions, but require more yard space.

Finally, if you have more questions or would like a free consultation, please reach out to our team at Otto ADU. We love everything ADU, and would be happy to help you on your journey.

Garage ADU Conversion Case Studies

Case studies of successful garage conversion ADUs can provide valuable insight into what it takes to transform a garage into a functional and attractive living space. Here is a selection of garage conversion projects recently completed by Otto ADU in Los Angeles City, Santa Monica, South Pasadena, Pasadena, Culver City, Glendale, and Los Angeles County.

Get in touch today to get a free project quote.

“Otto turned our garage into a beautiful ADU and now our 97 year old grandmother can live closer to us.

John & Julie