What Is a Bump-Out Addition? And How Can You Add One?

Are you caught between needing more space in your home but not wanting to pay for a full-size home addition? Building a bump-out addition could be a great compromise. Popular among cost-conscious homeowners, bump-outs are a smart way to expand the square footage of your house—without breaking the bank. Here’s what you should know about adding a bump-out addition to your home, including the pros and cons and the process of installing one.

What Is a Bump-Out Addition?

Bump-out additions (also known as micro additions) extend the size of an existing room in your home, often by just a few feet (although they can go up about 15 feet). Compared to other types of home additions, bump-outs are smaller in size, take less time to build, and are more affordable. You can add them to different kinds of rooms, including kitchens and bathrooms. Some homeowners even choose to install a garage bump-out addition for more storage or parking space.

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How Does a Bump-Out Addition Differ From a Regular Home Addition?

Regular and micro additions serve the same purpose: increasing the usable space in your home. However, bump-out additions cost far less than full-size ones because they’re smaller and require fewer materials. Plus, you can choose to cantilever a bump-out off the side of your home or your existing foundation, so you won’t have to pay for extra foundation work—unlike a regular home addition.

On average, a bump-out addition cost ranges from $4,000 to $30,000, whereas a traditional home addition costs between $22,350 and $81,260.

Common Types of Bump-Out Additions

Bump-out additions can enhance all types of rooms across your home. Some common purposes of bump-outs include: 

• In the kitchen: for a breakfast nook, extra cupboards, or a pantry

• In the bathroom: for a vanity or bathtub

• In the living room: for extra seating or shelving

• In a bedroom: for a walk-in closet or sitting area

If you’re hoping to build a new room, then a bump-out likely isn’t the right option for you. Instead, you’ll need to consider a regular home addition, which is more expensive and time-consuming than a bump-out addition. For example, the typical primary bedroom addition costs between $35,000 and $84,000.

Pros and Cons of Bump-Outs

Like any other home improvement project, there are pros and cons to building a bump-out addition. A bump-out addition provides extra space at a lower cost than a full home addition and can boost your home's value. However, it reduces outdoor space, and any required wiring or plumbing projects will increase the cost.

Bump-Out Building Codes

Local cities and counties have specific size and safety guidelines that you must follow when building your bump-out addition. These codes ensure your addition will be safely constructed and, in some cases, in harmony with the neighborhood’s architectural standards. For example, some codes limit the bump-out to a certain percentage of the existing floor area or require it not to encroach on setbacks or easements.

Building codes may also require a bump-out to have a certain foundation depending on its size, the nearby soil conditions, and your local climate. Some building codes mandate a full foundation, a crawl space, or allow for cantilevered designs without additional foundation work. Electrical and plumbing installations within the bump-out are also regulated, which can impact your project's complexity and cost.

Failure to follow local regulations can result in fines, legal issues, and potential safety hazards. It’s important to consult with the local building department or a home addition professional near you to make sure you comply with building codes.

Process for Adding a Bump-Out Addition

Preparing for a bump-out addition is similar to planning a home addition. Here’s what the process usually looks like.

1. Determine why you’re building a bump-out. Before doing anything else, specify the purpose of your bump-out addition—whether that’s adding more counter space in your kitchen, a bigger closet in your bedroom, or a tub in your bathroom. Need some inspiration for your bump-out project? Check out these kitchen bump-out ideas.

2. Set a budget. The cost of your bump-out will depend, in part, on its size. For example, a 2-by-10-foot bump-out typically costs around $10,000, while a 4-by-10-foot bump-out costs $30,000 or more. 

3. Contact a structural engineer (optional). Depending on the type of project, such as a cantilever-style bump-out, a structural engineer ensures the addition is structurally sound and complies with safety standards. Bump-outs require precise calculations to support the extended space without additional foundation work.

4. Reach out to a local home addition company. Once you’ve defined your purpose and budget, speak with a home addition pro to get a quote for your project.

5. Kick off the project. After you’ve chosen a home addition company, they’ll manage the entire building process, including permitting, design, and construction.

Adding a Bump-Out Yourself vs. Hiring a Pro

While it is technically possible to build a bump-out addition yourself, it isn’t the most beginner-friendly DIY project—particularly if it involves electrical or plumbing work. For that reason, we recommend working with a home addition company near you if you’re interested in adding one.

DIY-ing a bump-out addition is not recommended due to the complex structural work involved. The project requires precise knowledge of load-bearing calculations, building codes, and safety standards. Improper construction can lead to structural failures, safety hazards, and costly repairs. Professional builders and engineers have the expertise to design and execute the project to ensure it's safe, compliant with regulations, and seamlessly integrated with your home.