When you're planning to extend the living space in your home, it's helpful to look for existing space that can be renovated. Converting a basement or attic to a bedroom, office, or other purpose can be much easier and more cost-effective than putting on an addition.

The garage isn't often considered for this type of project. But an attached garage can easily add several hundred square feet to your residence, giving it an alternate purpose such as a home office or children's playroom. Detached garages can be transformed into a guest house, artist's studio, or similar getaway.

This type of renovation will require careful planning. The garage will likely need significant work in order to be seamlessly integrated into the home. You'll also need to consider some potential disadvantages in the project.

Requirements

Although you're working with an existing space, it's still likely that you'll need to get a permit for the garage conversion. Lee Wallender, writing for the home design site The Spruce, says you'll need to meet a number of requirements before the garage is considered habitable space. Check with your local building department before starting the renovation.

In general, the garage will need to be comfortable and usable to those spending more time there. Oliver Marks, writing for the home improvement site HouseLogic, says the space will need heating and cooling, either by an independent system or a connection to the home's system. The space will also need to be insulated, including an elevation of the floor to provide insulation over the concrete slab, with a moisture barrier to prevent damage to new flooring. The electrical system will likely need to be updated to provide more outlets; plumbing may be necessary as well.

If you're looking to create an open floor plan with the rest of the home, you'll need to knock down the partition between the garage and residence. It may be necessary to add new windows and doors to the garage to let in more natural light and provide a point of egress.

The large garage door can sometimes be a challenge in this type of renovation. Stefan Lucian Gheorghe, founder of the interior design site Homedit, says walling off the door will make it harder to convert the space back to a garage if a future owner wishes to do so. One option is to leave the door in place, but cover the interior with a wall. The space can also be used for a large window, or a windowed door which can be opened by running along the existing tracks.

The project can involve substantial costs. Oseye Boyd, writing for Angie's List, estimates that a garage conversion will cost about $10,000 to $15,000, with additional costs if plumbing work is necessary. The home improvement site HomeAdvisor says typical project costs range from $20,000 to $50,000.

Converting the garage to living space is also an in-depth project, so it will require a good deal of time. The work generally takes about four to six weeks.

Pros

The most obvious benefit of a garage conversion is that it will increase the size of your home. Cottage Industries, a home remodeling company based in Wayne, Pa., says this can improve the functionality of your home and boost its value as well.

While many additions require you to expand your home's footprint, changing the use of the garage can be done within the existing structure. This, in turn, means you don't have to lose any of your yard space.

The project will also be cheaper than building an addition because much of the structure is already in place. Wallender says that while you'll still need to do a considerable amount of renovation work, you'll at least have the walls and roof in place.

If you are reasonably handy, much of the process of converting a garage can be a do-it-yourself job. You'll naturally want to hire a professional for work such as expanding the electrical or plumbing systems. But you might opt to install drywall, add paint, and complete other steps on your own, significantly reducing the costs of the work.

Depending on your tastes, you may be able to get a truly unique home style. Gheorghe says it's possible to establish unique zones in a converted garage, leaving enough room to park the car in the corner of your new den.

Cons

Converting a garage can create more useful space in your home, but it can also displace your vehicle and many of your belongings. A1 Garage Door, a company in Madison, Wis., says you'll need to find a new place to store your vehicle as well as any other items in the garage, which may include the lawn mower and your collection of tools.

Some items can simply be relocated to the basement or a shed, but you'll likely end up having to park your vehicle in the driveway or on the street. The garage protects your vehicle from sunlight, snow, and theft; leaving it in the open will make it more vulnerable.

You'll also need to carefully consider the design of the new living space. Cottage Industries says a converted garage may not look like a natural area of the home if it is not seamlessly integrated into the residence.

While converting the garage can boost a home's value by increasing its living space, it can also have the opposite effect. Wallender says buyers may be disappointed that the home doesn't have a protected area to park a vehicle, which in turn brings down the appeal and value of the property.