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ADU Above Garage: What You Should Know

Above-garage ADUs help you maximize your space by building up instead of out. Learn more about this type of ADU and how to build one with Cottage.

January 1, 2018

If you’re in serious need of some extra space but aren’t sure where you could possibly get it, you may consider building an ADU above your garage. This intelligent solution could provide you with the space you need without sacrificing storage, living, or outdoor space since you’re building up instead of out.

Here’s everything you need to know about building an above-garage ADU:

Can You Build an ADU Above a Garage?

Building an ADU above your garage is possible with the right planning and due diligence. Building an ADU above an existing garage can be a great way to maximize your space and is ideal if you don’t have the extra space needed to build a completely detached ADU.

Note that building an ADU above a garage isn’t necessarily an easy or straightforward process. Cottage is here to guide you through the process and help you make the right decision based on your property and needs.

Why Build an Above-Garage ADU?

Now that we’ve established that it’s indeed possible to build an ADU above a garage, let’s talk about some of the reasons why you would want to undertake this project:

Guest Space

For starters, building an above-garage ADU could provide you with a great space to host guests when they come into town. Your guests will appreciate having a private area of their own. However, the area isn’t so big that they will overstay their welcome.

Office Space

If you’re permanently working from home and are in need of a separate office where you can work in peace, then an above-garage ADU might be the perfect solution. You can incorporate everything you need for a working space, including a half-bathroom, a mini-fridge, coffee maker, etc.

Rental Income

Building an above-garage ADU also has investment potential. If you rent out the unit either on a short-term or long-term basis, you could easily earn back what you spent on the project and then some.

Just make sure to check rental regulations for your local area. For example, in many places in California, you’re only allowed to do long-term rentals rather than short-term vacation rentals.

Pros and Cons of Building an Above-Garage ADU

Here are some of the pros and cons of building an above-garage ADU so that you can make an informed decision:


  • Save yard space: Since you’re building up instead of out with an above-garage ADU, you’re not really losing any room in your yard. You’re also not sacrificing your garage space like you would be with a conversion ADU. Essentially, building an above-garage ADU might be the best way to maximize your space.
  • Increase home value: There’s no doubt that adding an above-garage ADU adds value to your home. Just how much value it would add depends on the type of ADU, the size of the addition, and the finishes used. For instance, if you’re able to add a full bedroom and bathroom, you can expect to see a large boost in your home’s value.
  • Private and cozy: Whether you’re building an above-garage ADU to house the occasional guest or allow an adult child to live rent-free, this approach creates a private and cozy spot that’s separate from the main house and has just enough room for the essentials.


  • Higher costs: While building an above-garage ADU might seem like a cost-effective solution, it’s actually more expensive than you’d think. At the same time, you may be able to get a good return on your investment.
  • Limited space: While some people would call above-garage ADUs “cozy,” others would call them “cramped.” Depending on the size of your garage, it might be best suited for short-term guests rather than long-term residents.
  • Rules and regulations: When building an above-garage ADU, you need to follow a litany of rules and regulations. You also need to obtain permits from the proper authorities. Navigating through this intricate process can be complicated, which is why you may want to consider working with an ADU expert like Cottage that can help guide you through every step of the process.

How Much Does It Cost To Build an Above-Garage ADU?

So we’ve established that it can be costly to build an above-garage ADU, but how much are we talking about? On average, it costs anywhere from $50,000 to $150,000 more to build an ADU on top of an existing garage than the equivalent ADU size on a single floor or conversion of the garage itself.

Here are some of the main reasons for this higher cost:

Building an Above-Garage ADU Is Structurally Complicated

This is because the extra story needs extra support to be structurally sound. At the same time, you likely won’t be able to add any support posts on the first floor of the structure that would make it less functional. Instead, you have to build up the perimeter of the structure while also adding several layers of subfloor.

Many Garages Are Older Structures That May Require Extra Work

Depending on the age of the house, you might be dealing with an older structure that needs some updates and fixes. Building codes have changed a lot over the years, and it can take a lot of time and money to bring things up to 21st century codes.

Building an Above-Garage ADU Requires Stairs and a New Roof

Compared to a conversion ADU product, building an above-garage ADU means that you need to build stairs to the second-story unit and add a new roof for the addition. A new roof on its own can cost several thousands of dollars and stairs aren’t cheap, either.

It can Be Difficult to Match the Style and Materials of the Existing Garage

If you’re looking for a cohesive look between the existing unit and the new unit, you’re going to need to use the same materials.

So, hypothetically, if your existing garage is built with a specific type of siding, it might be challenging or expensive to locate the exact same type of siding for the addition. It might also be challenging to replicate the right paint color without having to repaint both floors of the entire garage.

Other Types of ADUs to Consider

Depending on your garage, you could build either a detached or attached ADU on top of that existing space.

Here’s what you need to know about the different types of ADUs:

Detached ADU

A detached ADU is a unit that’s detached from the main house. So if you have a detached garage and decide to build it up, you would be building a detached ADU. And while building a detached ADU might seem complicated, it can be more straightforward than the other options.

Attached ADU

An attached ADU is a unit that’s attached from the main house on at least one side. So if you have an attached garage and decide to build it up, you would be building an attached ADU. Simply building onto your home may seem like an easy solution, yet, there are safety and fire standards to follow that can complicate the construction process.

Conversion ADU

A conversion ADU involves converting an existing space into a separate unit. For example, if you simply convert an existing garage space into an ADU by adding a bathroom and kitchen instead of building upwards, that’s a conversion ADU. Conversion ADUs can also be made from basements or even spacious spare bedrooms.

What Do You Need to Build an ADU?

Before you move forward with your ADU build, here are the three things that you need to build an ADU:

Step 1: Space

For starters, you need space to build an ADU. And now that you’re familiar with the different types of ADUs, you know that you don’t necessarily need extra space in your yard for a traditional detached ADU.

Instead, you could utilize existing space in your home to create a conversion ADU from a basement or build up from an existing garage to create an above-garage ADU.

Step 2: Plan

Next, you need a plan for your ADU as this is a big project that should be taken seriously. Before you begin, you need to think about what you’re trying to accomplish by building an ADU.

Are you looking for space for the occasional guest, space for a home office, or space for a long-term tenant? Your ADU plan will likely differ depending on your desired use.

Step 3: Professionals

Finally, you need professionals to help you build an ADU. You will likely need architects and designers to help you come up with a floor plan that’s functional and meets building codes. You will also need contractors and subcontractors to actually do the work.

Instead of hiring everyone individually, you may want to work with an ADU provider like Cottage. Cottage provides you with access to everything and everyone you need all under one roof.

Why Work With an ADU Builder?

Still not convinced as to why you should work with an ADU builder?

Here are some additional benefits to consider:


ADU builders have the experience and expertise you need to end up with a beautiful and functional ADU that meets your needs. Building an ADU isn’t the same as building a home or even renovating a home, so for that reason, you should consider working with expert ADU builders.


ADU builders also have the resources you need for a smooth process from start to finish. Cottage, for example, has a team of ADU architects and designers to help you come up with the perfect floor plan. Cottage also has a network of vetted, licensed, and insured contractors to help you bring your vision to life.


At Cottage, we give you the best value at every step of the process. From a free feasibility assessment for your above-garage ADU, to providing multiple competitive bids from our network of vetted contractors, you'll know you're getting best-in-market value and fair pricing.

How To Work With an ADU Builder

That being said, not all ADU builders are created equal. In order to enjoy all of these benefits, you need to work with an experienced and reputable builder like the ones found on the Cottage platform.

Cottage works with homeowners to create custom ADUs that meet their unique needs. So if you’re interested in building an above-garage ADU, reach out to the ADU experts at Cottage for more information.

Final Thoughts

Building an ADU above your garage is a unique solution to the common problem of needing more space. To maximize your layout and meet all your needs, work with Cottage to design a custom ADU.

Check out some of Cottage’s previous projects, standard floor plans, and ADU resources before scheduling a site visit.


What You Need to Know About Long-Term Vs. Short-Term Rentals | Forbes

8 Ways to Boost Your Home Value | Consumer Reports

ADU Handbook | California Department of Housing and Community Development