With the rise in multigenerational homes, more and more families need additional space in the garage to park a third or fourth car. Now many homeowners are wondering how they can transform their standard garage into a bump-out.  In this article, we’ll discuss garage addition ideas and how you can successfully complete a garage addition to an existing garage.

What is a garage bump out?

A garage bump-out is additional space added to a garage to create more room for an additional car or some other purpose. There are many benefits to having a garage bump-out addition. Any time you increase the square footage of your home, you are bound to see an increase in the value of your home. This is both beneficial in the short and long run.

One of the first things you must determine about expanding a garage is what you’d like to use the space for. Some garage add-on ideas include using the space as a workshop, a new laundry area, or additional storage. A garage bump out can also be used to store other items like bicycles, motorcycles, scooters, snow sledges, etc.

Plan for a garage extension

Sometimes, we use the garage to dump all the items that have nowhere to go. Boxes of old clothes, decorations, or old equipment that no one knows what to do with tend to end up in the garage.

So, the first thing you need to do is declutter your garage. If you have anything that is unnecessary and just takes up space, get rid of it so that you can reinvent your garage space. If you have a lot to discard, consider renting a dumpster to make it easier to dispose of junk. Once you have done this, you can now focus on the garage add-on.

Establish garage expansion cost

Take some time to determine what your budget will be for this project. How much you will need to set aside for this project will depend on how much extra space you need. Do you need another carport, or would you like to create a smaller space to serve another purpose?

On average, you can expect to spend somewhere around $6,250 for an additional carport. This figure will climb if you have other intentions for the space and plan to use it for a different purpose. In this case, the cost can be anywhere from $10,000 to $25,000.

Tools required for garage bump-out

Before you start, make sure you have everything you need for equipment. You’re going to need carpentry tools and some heavy-duty equipment to get the job done properly.

You will need:

  • Hammer drill: You’re going to need this to drill in nails into the hard surfaces. This is necessary for creating a solid foundation on which you will build your garage bump out.
  • Concrete anchors: These are very large and thick screws that are used to secure the wooden beams to the concrete in your foundation.

  • Tie plates: These are silver plates that are used to provide support for the bump-out.
  • Reciprocating saw: This is a power saw that is used to cut wooden beams to the appropriate size.
  • Level: Use this tool to ensure that your walls are straight and even.
  • Ladder: You need this to reach higher parts of the wall and to install roof shingles, gutters, and any high storage shelves you plan to add to the space.
  • Safety goggles: Anytime you’re working with concrete and wood, there is bound to be a lot of dust and debris floating in the air. To protect your eyes, ensure that you have a good pair of safety goggles.
  • Gloves: Protect your hands from splinters or cuts from sharp tools by wearing gloves.

Materials needed to build a garage bump-out

The first thing that we need to state is that the materials you get need to be durable so they can withstand harsh weather conditions and everyday wear and tear. Keep in mind that the external part of your garage bump out should match the exterior of your garage. If it doesn’t, your addition will look odd.

The materials you will need include:

  • Wooden beams: These are needed to support the foundation and provide an outline for your walls.
  • Wall studs: This is the wooden framing that will give your addition an outline.
  • Double trimmers: These are metal beams that support the walls and become the header of your bump-out.
  • Plywood: This is used to form the roof of the extension and the foundation as well.
  • Concrete: This fills in the space in your foundation, floors, and on your walls.
  • Roofing felt: This is a thin underlayment that serves as a protective layer for your roof by keeping moisture out.
  • Vinyl siding: You’ll need this for a finish on the exterior of your extension. As stated before, this should match the siding used on the rest of your garage.

How to Build Onto a Garage

One of the first decisions is determining which wall you should use to build out your garage. Choose a wall that is not surrounded by outdoor fencing so you’ll have enough space to add the extension.

The steps you should take include:

STEP 1: Build a header

Create an outline for the bump-out wall using the wooden beams and the double trimmers. Doing this will ensure that your roof is supported once you break down the wall. You can only do this on your own if you have a single-story garage. If you have a two-story garage, it’s imperative that you hire a general contractor to install the header so it does not compromise the structural integrity of your home. Once this has been done, you can now outline your garage addition by doing the following:

a) Find an inappropriate spot: Choose where you want your bump-out addition and mark it.

b) Mark opening: Make two 3-inch marks beyond the opening of the indoor pump out, making sure that the inside opening is 7 inches narrower than the width of your extension.

c) Cut the header: This is where your reciprocating saw will come in handy. Use it to cut two 10-inch headers and nail them together. Once this is done, nail a 2 x 4 to the bottom of each header that will be attached to your garage.

STEP 2: Remove the existing garage wall

After outlining the garage addition, the next step is to tear down the existing wall. You need to have an understanding of the structure of your garage to ensure that you do not tear down any load-bearing walls. This is where we advise you to seek the input of a professional inspector to determine which walls are critical to the structure of your garage. After determining which wall is structural, you can choose one of the remaining walls for your bump out.

STEP 3: Make a base

a)    Use your hammer drill and concrete anchors to build the foundation of your garage bump-out extension. The first thing you need to do is mark the spot using a 12-foot piece of plywood and nail it into the existing wall. This should be 18 inches above your garage floor.

b)    Then, make holes by digging two holes that are 1-foot deep where the posts of the extension will be placed. These should be 12 feet apart.

c)    Next, you need to fill in the holes by pouring 8 inches of concrete into each of the holes.

d)    Once this is done, install the posts. This should be conducted after the concrete has had time to set. To accomplish this, install two posts that have been treated. They should be 4 x 4.

e)    The next step is to secure the foundation. Place soil around each of the posts but be careful not to allow any dirt to get under the joists.

f)     The next step is to frame the floor. This is done by connecting the posts with a wooden beam that is 12-feet long using hurricane ties. Carefully measure the distance from the beam to the existing garage floor and cut four pieces of plywood based on this length. Each of these pieces should be secured to the garage and beam, ensuring that they are 3 feet apart.

g)    The final step is to attach the header. Using your existing garage wall, secure the header and bump-out floor using hurricane ties.

STEP 4: Building the walls of your bump-out addition

The first step to building your walls is to begin on a flat, firm surface. Start off with building a taller wall that will be 12 feet tall.

a)    To do this, use the length and width of your bump-out opening and add 3 inches to the length and 7 inches to the width.

b)    Cut four wooden beams to fit these measurements – two for the length and two for the width. At the end of each of the longer beams, mark stud locations.

c)    Once you have done this, the stud locations will be where you nail the short and long beams together.

d)    Stand the wall up and nail it to the bump-out floor.

e)    Next, you’ll need to build the two shorter walls. These will be approximately 5 feet each. Measure the front of your extension, then cut four wooden beams based on the height and width of the taller wall. This will help you build your short walls.

f)     Connect the walls together using tie plates that have been cut according to the measurement of your long and short walls. To reinforce the walls, screw the short walls to the bottom plate of the garage floor.

g)    Next, you will need to finish the walls with the tie plates on both walls, and make sure that they do not touch.

h)    The final step in this stage is to secure the outline which involves attaching the outline using the level and concrete anchors.

STEP 5: Add a roof

Once the walls are in place, the next step will be to add your roof and cut the rafters.

a)    The first step in doing this will be to mark the middle of the bump-out addition using chalk and making sure that it is parallel to your roof.

b)    Next, select an area for your rafters. Use the chalk to make two additional markers on your roof’s overhang and the end of your bump-out. You will cut the rafters to this size.

c)    Install the rafters one by one. The first one should be installed on the left side of your garage wall, ensuring that it is installed from the center mark to the overhang. Repeat this on the right side of your garage.

d)    Reinforce rafters using metal hurricane ties.

e)    Connect rafters by installing a 2 x 6 piece of wood at the point where your rafters meet and nail them in place.

f)     Install gable trusses. These are the wooden beams that provide support to your roof. Install them from the header to the end of each raft. There should be three on each side when you are done.

g)    Lay down the plywood and roofing felt over the gable trusses with the plywood going first and the roofing felt on top of the plywood.

h)    The final step is to shingle the roof. Using a staple gun, install shingles using a pattern that matches the rest of your roof.

STEP 6: Install vinyl siding

Once the walls have been erected and all of the steps above have been followed, the next step is to add vinyl siding. As with the roofing, you want to use a similar vinyl style and colour to finish the garage. This is so that your extension can blend in with the rest of your home.

a)    The first step is to install one row of siding. Beginning at the foundation of your garage bump-out addition, install the first row of vinyl siding and secure it in place using a nail. Be sure that each additional piece overlaps this by 4 inches. Keep the pattern straight. Make sure that the pattern remains aligned as you continue to add to the siding.

b)    Once this is done, cover the entire wall using the same process until it is completely covered with vinyl siding.

c)    The final step is to secure the corners by installing channels where the siding ends.


Is a garage bump out worth the investment?

Yes. Garage bump-outs are one of the most popular types of home additions because they are not complex projects and add value to your home.

Should I do other projects at the same time?

We recommend focusing on one area of your home at a time. A garage bump-out addition can be completed in a few days, freeing you up to work on another project soon after.

Contact Us

Connect with our team at Aria Build for valuable insight on bump-out additions and other home-improvement projects. Reach out to our team today if you have any questions or concerns. Our friendly team will be happy to answer your questions.

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