How to Add a Garage Addition to an Existing Garage

The average size of a one-car garage is between 12 and 16 feet wide, with a depth of 22 feet. However, for many homeowners, it’s simply not enough space. Whether you need extra storage space or want to create a workshop, adding a garage addition to your existing garage makes sense.

But before you start expanding your garage, careful planning is essential. You’ll need to decide on the right type of addition, estimate costs, and ensure your project complies with local building regulations. If not, you may make a costly mistake and waste time.

This guide covers everything you need to know about adding onto your existing garage, from initial planning to final construction.

Step One. Establish Why You Need the Extra Space

Before you go gung-ho adding a new garage to your existing one, it’s essential to determine what you want and need. Here are some factors to consider:

• How much extra space do you require?
• What is the purpose of the additional space (e.g., storage, workshop, living area)?
• Do you have enough room on your property for an expansion?
• Will your current garage design allow for an addition?

Knowing this information can influence your new garage addition’s eventual layout, size, and overall cost.

Pro Tip: Declutter your existing garage before committing to an addition. Organizing and purging unnecessary items might free up more space than you expect. For larger items, consider renting out a storage unit. Storage facilities in London, for example, now offer units up to 200 square feet to accommodate larger items like furniture or seasonal equipment.

Step Two. Determine Accessibility and Placement

Once you’ve defined your garage requirements,  you’ll need to pick a spot for your new addition. Placement and accessibility not only affect the convenience of using your garage but also impact its compliance with local laws.

Follow the steps below to determine the ideal location for your new garage addition:

1. Choosing the Right Placement

Here are the most common areas to place a new garage:

• Side Extension: Common for converting a one-car garage into a two-car space.
• Rear Extension: Ideal for extra storage without altering curb appeal.
• Front Extension: May require driveway modifications and special permits.
• Second-Story Addition: A great option when lot space is limited.

2. Driveway and Entry Adjustments

Next, you’ll need to consider the placement of your driveway and entryway in relation to the new garage. This may mean modifying existing structures or creating new ones to ensure proper flow and accessibility.

Keep the following in mind:

• Driveway size: Make sure your driveway is wide enough to fit vehicles comfortably and allow for easy maneuvering.
• Property slope: Consider how your new garage will handle water runoff and accessibility. A downward slope may require drainage solutions like French drains or grading adjustments to prevent water pooling.
• Garage doors: These may need to be replaced or repositioned to fit the new garage addition.

Step Three: Check Property Lines and Setbacks

Now it’s time for the nitty-gritty details. Before beginning construction, it’s essential to check your property lines and setbacks to ensure you’re not encroaching on any neighboring properties or violating local building codes.

Most municipalities have zoning laws that dictate how close you can build to your property lines. Be sure to:

• Check setback requirements to avoid encroaching on your neighbor’s land.
• Confirm whether easements or underground utilities impact where you can build.
• Obtain a site plan if required for your building permits.

By ensuring your garage addition is within the proper boundaries, you can avoid costly disputes with neighbors and potential legal issues in the future.

Step Four: Set a Budget

You’ve envisioned how your garage addition will look, calculated how much space you need and have a solid plan in place.

The next step is knowing how much it will cost.

While costs vary based on location, materials, and labour, a garage addition typically ranges from $5,000 to $30,000 for a standard expansion, with larger or more complex builds costing more. Keep in mind that these are US national averages, so check with local contractors for more accurate estimates.

When setting a budget, consider the following factors:

• The cost of materials, including lumber, roofing, and siding.
• Labour costs for hiring contractors or doing it yourself.
• Permits and inspection fees.
• Any additional features you want to include in your garage addition, such as custom storage solutions or windows.

We highly recommend hiring a professional contractor for the construction of your garage addition to ensure it meets all safety and building code requirements. However, if you have experience in construction and feel confident in doing it yourself, be sure to carefully research materials and budget accordingly.

Step Five: Gather Your Materials & Begin Construction

Before we get to the fun part of building your garage, you must gather all necessary materials and tools. This includes the following:

• Framing: Lumber for walls, support beams, and studs.
• Foundation: Concrete, gravel, rebar, and formwork materials.
• Roofing: Rafters, plywood, shingles, roofing felt, and flashing.
• Siding & Insulation: Vinyl, wood, or brick siding, plus insulation for climate control.
• Doors & Windows: Standard or custom garage doors, windows, and entry doors.

If you’re taking on parts of the build yourself, ensure you have the right tools:

• Hammer drill and concrete anchors for the foundation.
• Reciprocating saw for cutting beams.
• Level and measuring tape for accuracy.
• Ladder and scaffolding for roof work.
• Safety gear, including gloves, goggles, and dust masks.

Step Six: Begin Construction

Now that you have all your materials and tools ready, it’s time to bring your garage addition to life. Follow these general steps:

• Prepare the Site: Clear the area of any debris or obstacles. Use stakes and string to mark out the exact dimensions of your garage addition.
• Dig & Pour the Foundation: If required by local codes, dig footings before pouring a concrete slab to create a solid foundation. Allow it to cure before building.
• Frame the Walls & Roof: Use lumber and standard framing techniques to build the walls, secure roof trusses, and ensure structural stability.
• Install Siding & Doors/Windows: Once the structure is up, add exterior siding, install doors and windows, and weatherproof the garage.
• Finish the Interior: Add insulation, drywall, flooring, and any custom features like shelving or storage solutions.

With the construction complete, your garage addition is ready for final touches to make it fully functional and seamlessly integrated with your existing space.

Is it Worthwhile to Expand Your Garage?

The short answer is, yes! However, it hinges on how well the job is done. If rushed, you could end up with structural issues, poor insulation, or a space that doesn’t fully meet your needs. 

A well-planned and properly built garage addition, on the other hand, can add significant value to your home, improve functionality, and provide much-needed storage or workspace. Just make sure to do your research, follow local codes and regulations, and take the time to construct it properly. Your future self (and potentially future buyers) will thank you!