The cost to convert a garage into an ADU ranges from $58,000 to $173,000, with an average of $115,000 depending on materials, size, condition, and labor fees.
The cost to convert a garage to an ADU—or an accessory dwelling unit—often ranges from $58,000 to $173,000 depending on its size and the features you include. The majority of homeowners spend an average of about $115,000 when they convert their home garage into an ADU.
This remodeling project may come with a hefty price tag, but it also yields a hearty return on investment should you decide to sell your home down the road. Until then, an ADU lets you provide a liveable space for your loved ones. Here’s how to budget for your garage to ADU conversion.
Converting a garage into an ADU requires more planning, permitting, and money than simply turning a garage into additional living space, such as a bedroom or entertainment room. An ADU is an independent living space that must contain its own kitchen, bathroom, and other features, many of which depend on regulations in your area.
Be prepared for a larger price tag, closer to the cost of building an in-law suite, and more stringent construction rules from your municipality.
Garage size is a major factor when converting a garage to an ADU. Converting a two-car garage will cost less than converting a three-car garage. However, calculating the cost difference between large and small isn't linear due to the need for infrastructure like sewer, plumbing, HVAC, and electricity, which aren’t dictated simply by the size of the space.
In some jurisdictions, a one-car garage doesn't have enough floor space to qualify for ADU conversion unless you add a second story. Here’s a look at the average price of garage ADUs based on common garage sizes.
| Garage Size One-car | Average Square Footage | Average Price Range |
|---|---|---|
| One-car | 240 | $39,000–$87,000 |
| Two-car | 360 | $58,000–$173,000 |
| Three-car | 704 | $66,000–$239,000 |
The cost of materials when converting a garage to an ADU is highly variable. Often, materials make up between 40% and 50% of the project's cost. However, if the existing garage is in excellent condition, material costs land on the low end of that range.
Because of its small size, converting a garage to an ADU requires an excellent design plan to create a functional and comfortable home space. Two professionals—a designer and an architect—should be considered during the planning stages of your ADU.
The cost to hire an architect depends on their experience and the project size. For a garage conversion, expect a price between $2,000 and $6,600 for a set of plans. You'll likely need to obtain a building permit and outline the project for the various tradespeople who'll build the ADU.
In addition to hiring an architect, you may want to hire an interior designer to help ensure the dwelling unit lives up to its potential. Interior designer prices range from $50 to $200 per hour.
Your municipality will likely require you to get a building permit for ADU construction or any garage conversion. Because garages aren't intended as living spaces, turning one into a home can require significant structural changes.
Many municipalities will accept basic plan drawings when you apply for a permit. However, some will require a structural engineer to sign off on the plans before issuing a permit. The cost to hire a structural engineer ranges between $70 and $250 per hour.
When converting a garage to an ADU, your carpenter will likely be one of the first tradespersons necessary. Garage conversion requires building a wall where the garage door exists and installing windows and doors. The average cost of carpentry is between $75 and $100 per hour. However, the cost of installing cabinetry or other specialty items can vary from that norm, and each task may have a different associated cost.
An ADU will need its own heating and cooling system to be legal in most locations. Installing a cost-effective and efficient system, such as a heat pump, costs between $3,900 and $5,900.
Your plumber will be crucial to the project's success from the start. Converting a garage to an ADU requires sewer, supply lines, rough-in, and finish plumbing.
Sewer line installation: $1,435–$5,735
Rough-in plumbing for a bathroom and kitchen: $1,600–$2,900 each
Installing a sink: $220–$645
Shower installation: $500–$3,000
Toilet installation: $225–$533
Faucet installation: $160–$365 each
You’ll save some money if electricity already exists in the garage. However, an electrician will need to add additional circuits and ensure the ADU electrical meets code requirements for a living space. Like the plumber, the electrician must perform rough-in work and then return to complete the installation.
Running electricity to a detached garage: $1,000–$3,000
Outlet installation: $130–$300 each
Installing a light fixture: $155–$955 each
Installing a dedicated circuit: $570–$1,000
Depending on the climate where you live, municipal regulations, and how energy efficient you'd like to make your ADU, the cost to install insulation in the walls and ceiling or roof will be between $1,065 and $2,600 or more for a typical two-car-sized garage conversion. Your conversion may require more than one type of insulation, depending on climate and its configuration.
| Insulation Type | Average Cost Range |
|---|---|
| Fiberglass | $360–$1,800 |
| Cellulose | $720–$2,760 |
| Rock Wool | $1,680–$4,800 |
| Polystyrene | $300–$600 |
After the HVAC, plumbing, and electrical rough-in work is complete, your ADU will need wall covering. The most common wall covering is drywall. The cost of professional drywall installation, including labor and materials, runs between $1.50 and $3 per square foot.
A little paint goes a long way in putting the finishing touches on the new living space. While you can also choose finishes like wallpaper, tile, or paneling, your ADU will likely require at least some paint.
Painting cost: $2.75–$4.70 per square foot
Wallpapering cost: $315–$820
Tile installation cost: $5–$45 per square foot
Paneling installation cost: $1–$40 per square foot
Your ADU may contain more than one type of flooring material. The average cost of flooring varies by type, style, quality, and size. However, covering roughly 500 square feet, or the approximate finished space of a single-floor two-car garage conversion, will cost an average of between $1,530 and $4,850 or more for premium materials.
| Flooring Material | Average Cost Per Square Foot |
|---|---|
| Carpet | $3.50–$11 |
| Tile | $15–$20 |
| Wood | $6–$25 |
| Engineered wood | $4.50–$16 |
| Laminate | $3–$13 |
| Vinyl | $2–$14 |
There's another easier but more costly way to convert a garage into an ADU without having to hire each tradesperson on your own. The cost to hire a general contractor varies by project complexity and scope but often adds between 10% and 40% to the total price of materials and labor. In some cases, you may be able to hire a contractor for portions of the job, such as kitchen or bathroom installations that require more skill and experience to accomplish.
Kitchen installation costs: $100 to $300 per square foot
Bathroom installation costs: $200 to $250 per square foot
While hiring a contractor costs more than performing the job yourself, many homeowners consider the price to be on par with hiring each individual tradesperson or company on their own due to the significant time they must invest when doing it alone.
You may also choose to hire a handyperson for some of the smaller tasks, such as finishing work or installations that require skills and tools you may not own. The cost to hire a handyperson is $50 to $150 per hour plus material prices and sometimes a markup of between 10% and 20%.
There are a number of additional cost factors to consider when converting your garage to an ADU.
The physical preparation necessary before ADU construction can start will depend on your garage’s condition. Things to consider include garage door removal, repairing any damage to the structure, ensuring the roof is in good condition, concrete floor patching, and dealing with any rainwater drainage issues.
When you convert a garage to an ADU, you are essentially building a home. Your municipality will require all of the same permits you’d need for home construction or at least for building an addition. If you choose to hire a contractor, plumber, electrician, or HVAC installer, they will obtain the permits they need for their part of the project.
If you decide to get the permits, you'll need a building permit and separate ones for mechanicals, sewer lines, and possibly others. A standard building permit costs between $500 and $3,000, depending on project scope and your municipality. Permits for electrical, HVAC, plumbing, and others often cost between $10 and $500 each.
Once construction of the ADU is complete, you can make it move-in ready by hiring a cleaning service to ensure all of the dust and debris is taken care of. The cost of construction cleanup ranges from $140 to $710.
Your property taxes and home insurance will likely increase after your ADU is complete. However, the amount is highly variable, based on everything from where you live to current property values, insurance prices and regulations in your area, and even market conditions. Speaking with an insurance and tax professional can be helpful before starting the project.
Should you choose to finance your home addition, remember to include the cost of borrowing money for the job in terms of interest rates, monthly payments, and reduced returns if you're borrowing from an investment account.
Acting as your own contractor when converting your garage to an ADU can save up to 40% of the job's cost. However, managing all of the comings and goings of the large number of tradespeople and inspectors required is challenging and time-consuming.
It is also possible to perform most of the work yourself without using many contractors. However, most jurisdictions won't allow an unlicensed homeowner to install most HVAC systems. Additionally, doing the work yourself requires a high level of skill in many trades. It also means taking the time to welcome the several inspectors who must sign off on certain portions as the project moves forward.
We recommend hiring a local home remodeling contractor early in the process of converting your garage to an ADU. A professional contractor can provide guidance and ideas and manage the entire project, from planning to final inspection and cleanup.
Some homeowners may be tempted to build a new standalone ADU structure on their property instead of converting a garage into an ADU. However, it’s often more cost-effective to convert the garage rather than start from scratch with new construction that adds to the footprint of your home.
Another option is to knock down your garage and build an ADU in its place rather than convert it. The benefits of replacing the garage with a new structure can include ease of access for sewer and a new foundation. This avoids the need to retrofit new materials into existing ones and allows you to build to code from the start instead of trying to bring old materials up to standards.
However, replacing the garage will cost more than simply remodeling a garage structure that already meets many building code standards. By converting your garage, you can save substantial material costs in lumber, foundation, and roofing supplies, as well as potentially avoid the need to reframe existing walls to contain windows and a door.
Deciding between converting your garage and building new construction is another area where hiring a contractor is helpful. The contractor can help you choose the most cost-effective, fastest, and overall best method of adding an ADU to your property.
Converting your garage to an ADU is a big project. Because of the project's scope, there are multiple ways to reduce the overall cost, even if you choose to hire a contractor. However, the best tip for converting your garage is to set and maintain a realistic budget. Here are a few other ideas.
Perform your own preparation work. Steps you may be able to do include patching the concrete floor and removing all of your possessions from the space.
Consider using upcycled or recycled materials for parts of the project. Ask your contractor for any restrictions, as some materials may not be suitable.
Don't attempt to remove the overhead garage door on your own. Garage door springs are under immense pressure, and improper removal can cause serious injury or worse.
In most cases, converting your garage to an ADU will increase the property value. Adding living space to a property can see investment returns of up to 40%. Additionally, if the new space will be a rental unit, it can even generate income. However, there are some factors to consider before jumping in.
In some locations, garage space is precious. Having a space that protects vehicles from harsh weather is a huge selling point for many home buyers. If you replace the garage with an ADU, effectively removing garage parking from the property, there's a potential to turn off some would-be buyers when it's time to sell.
Another factor to consider may be whether or not you want to be a landlord to the renters who move in. While the property value and your monthly income may increase, decide if having the additional responsibility is worth it to you in the long run.
"There is some demand in the market for ADU's, specifically in-law suites. Most of this is driven by new homebuyers looking for ways to help pay their mortgage by renting space without having to qualify for an additional loan to purchase a separate investment property. This has increased as mortgage rates have continued to increase and homebuyers look for ways to save."
— Maureen McDermut, Realtor at Sotheby's International-Montecito
The least expensive way to convert a garage to a living space is to perform as much of the work yourself as possible, using materials you can acquire at discount prices. However, performing the tasks necessary for the job requires skills in multiple homebuilding disciplines and a great deal of invested time.
Every homeowner will likely have a different opinion on whether converting their garage to an ADU is worth the time, effort, and cost. To help decide if the project is worth it, balance factors like increased property value and potential earnings against the more difficult parts, like financing costs, time investment, and loss of covered parking spaces on the property.
