Garage Addition Guide

In the US, 80% of homes and condos have a garage or carport, but they’re often only big enough for one car. So, many homeowners decide they need a garage addition to extend their existing garage. The other 20% may choose to add an entirely new garage.

Before you begin a garage addition project, though, you’ll need to determine what type of garage you want to add, how much this will cost, and what permits are needed for construction to begin. We outline everything you need to know below.

This is for informational purposes - always check with your permitted authority or regulatory body first.

A garage addition involves either adding a new garage to an existing home or property or expanding an existing garage. It is usually done to create space for an extra vehicle or for additional storage. It can also create a functional living space, like a workshop, gym, or living area. 

There are three main types of garage additions.

• Attached garage addition - This type is connected to the existing structure of the home, often sharing one or more walls.

• Detached garages - This type forms a separate structure built on the property, independent of the main house.

• Garage extension - This type extends the existing garage to make it a larger space, say from a one car space to a two car space.

• Addition over garage - This type adds a space above your existing garage. 

The cost of a garage addition varies based on the type of garage you want to build.

• Attached garage addition - The average cost of adding an attached garage is $26,000, but it can range from $10,000 to $43,000, depending on the number of car spaces and where you live.

• Detached garages - The average building cost of a detached garage can vary significantly. You can buy a no-frill prefab garage for a single car for about $1,500 but a custom separate structure garage with a mother-in-law suite can cost upwards of $50,000.

• Garage extension - Extending an existing garage costs between $5,000 and $30,000 on average.

• Addition over garage - The average cost to build an extension over a garage is $60,000 to $200,000, or $150 to $500 per square foot.

First things first, you need to choose the type of garage you want and the number of desired carports. You should do this based on both your budget and how much space you need. It’s worth noting that building an attached or detached garage will significantly affect the cost of the garage addition (see above).

When designing the garage, you need to consider accessibility and how the size, orientation, and shape of the garage will affect the current driveway. Depending on your design, you may need to alter or replace the driveway.

You will need to familiarize yourself with your local zoning laws, ordinances, and requirements for building a garage. If you use a building contractor for the project, they will help bring you up to speed. A contractor will also get permits for the build and inspections, if necessary, to ensure the garage is legal and compliant.

You can find information and documentation about local zoning laws and ordinances in your city building. They may also provide this information on the local government’s website for easier access.

A site plan illustrates an aerial view of your property, defining boundaries and features that can help visualize the garage addition. Many local governments also require them for building and zoning permits.

You may need to provide a site plan for the garage addition when your builder submits the permit applications. If so, consider our site plan and floor plan services for quick and accurate plans.

Even if you don’t do it as part of the initial build, you may want to mock up a floor plan for an Accessory Dwelling Unit (ADU) above your garage. Then you can evaluate the costs and include them as part of your build.

If you decide you don’t want to add the ADU now, you may want to incorporate all the necessary utility hookups. This way, the garage is prepped so that it is easier to add the ADU later.

Note: You’ll want to find out if your local zoning allows for ADUs on your property to ensure the living space is legal before you build it. You’ll need to submit floor plans for building permits if you decide to build it.

A garage addition provides your property with more storage, space, and curb appeal. You’ll want to evaluate zoning, design, and costs to ensure you can build the necessary garage space that you need. When you’re ready to submit the permit application to build your garage addition you will need a site plan. Luckily, MySitePlan can provide you with one in less than 24 hours.