Additional add-ons: how to get more space without the expense of a full addition

Would you like your kitchen to be a little bigger to accommodate a breakfast table? You might like a tub in your master bathroom, but none of the designs you found will fit. You can add just a few feet to your home without the headache and expense of a full-fledged room addition with a bump-out addition. Also known as a micro-add, if you think a bump-out would solve your design needs, this article will answer all of your questions.

What is a bump-out addition?

Typically, a hump addition is cantilevered over the existing foundation, similar to a balcony, making foundation work unnecessary. And, a micro-addition does not need to be tied to the existing roof line. These two qualities save time and money, while adding extra space.

The most noticeable difference between a bump-out and a room addition is the size. The bumps are small. Like just a few feet small, which obviously saves on the cost of materials. Bump-out additions are limited in size due to the fact that they do not have a separate foundation.

Additionally, micro additions rarely require additional heating or cooling. The vents in the room to which the bump-out connects will provide adequate service to the additional square footage. Do not run plumbing lines in the unheated area.

  • Keep reading: Addition costs at home – price per square foot, where to save and financing options

What size can you make a bump-out addition?

The weight of a cantilever bump is held by the house’s existing floor joists. The larger the joists, the larger your bump can be. According to Manny Angelo Varas, president and CEO of MV Group, South Florida’s luxury home builders, a floor joist can extend four times the depth of the joist. For example, if your joists are 2 x 10 inches, they are 9 ¼ inches deep. Multiply that measurement by 4 and your micro-addition can extend 37 inches.

Homeowners usually add extra additions to the first floor of the house. But you can also add one on the second floor. And, if your house is built on a concrete slab, you can always add a bump. According to Varas, a slab can support an overhang of 3 to 5 feet.

Reasons to add a bump-out addition to your home

Besides the cost savings, there are several reasons homeowners choose a bump-out over a full-fledged room addition. The most obvious reason is that they only need a few more feet inside the house. But there are also other reasons outside the home.

According to Varas, you’ll need a building permit for a micro-addition. So, before considering a home remodel, check with your building officials for permit requirements and zoning setbacks. If your home is already near your property line, your setbacks might be too tight for a full home expansion. It’s a great opportunity for a bump-out.

You might also consider a bump to protect mature trees and their roots. By cantilever the addition over the existing foundation, you can add space to your home without disturbing the soil. And tree roots aren’t the only thing underground. The foundation work required for an expansion of a full-size home may require moving plumbing or utility lines below grade. The work of moving these lines adds to the overall cost of the renovation.

Finally, if your yard is too small to accommodate the access and maneuvering of heavy equipment needed for foundation work, adding a bump-out always provides more square footage.

How much does a bump-out addition generally cost?

According to the online home services market, Home, the average addition of a room or house costs between $ 86 and $ 208 per square foot. At this rate, a typical home addition could cost $ 20,000 or more. But, since a bump-out lacks some of the factors that drive up the cost, a 2-foot micro kitchen add-on could cost as little as $ 5,000.

Two feet may not seem like much. But if you plan to run it the length of a 15 foot room, that gives you an additional 30 square feet. That’s plenty of room to add a breakfast table, pantry, or center island.

Why are replacement add-ons cheaper than a full add-on?

Since construction costs are often calculated by square footage, only the smaller size of a bump-out makes them cheaper than adding a room. However, other factors come into play. The lack of foundation is the main one. Other factors depend on the size and function of the add-on, which could mean you won’t need the following:

  • Wiring
  • Plumbing
  • HVAC ducts
  • Extension of the existing roof
  • As many windows as a complete room addition

Advantages and disadvantages of adding bump-out

Before discussing the pros and cons of a replacement addition, Varas advises homeowners to ask themselves, “Do you want to live in the house and just enjoy it, or do you want to create future value?”

Enjoying your home remodeling every day takes away the high cost of a full-size addition. But, if you only feel the pinch of a small dining room when everyone’s home for Thanksgiving, a bump-out and its smaller price tag may be your best option. Especially if you know you are home forever.

But, if you see yourself selling in the future, Varas says bump-outs don’t add much value to the home or provide a huge return on your investment. “A full-size addition creates future value for resale, unlike a replacement,” he says.

Otherwise, the pros and cons of adding a bump-out are:


  • Lower cost
  • Just enough space for what you need
  • Waste less garden space
  • Protect mature trees
  • Integrates perfectly into the existing structure

The inconvenients:

  • Adds space to a single room
  • You might have trouble matching your siding
  • Kitchen and bathroom dents may require plumbing lines, depending on your layout
  • Not for the average handyman

Ideas for additional additions

Varas says the most popular use of a micro-add is to enlarge the same space. Here are a few ways homeowners are using their accent additions to bring functionality and joy to the home.

  • Like a picture window with a window seat in the living room or den.
  • To expand the main bathroom, making room for both a tub and a shower.
  • In the kitchen, to add dining space, room for an island or pantry, or larger appliances.
  • To add a walk-in closet to a bedroom.
  • To add a laundry room or cloakroom.
  • As a home office, away from the family room.

Finally, always consult a trained professional before embarking on any addition to the home, especially a bump-out. If not properly supported, a cantilevered micro-addition can sag, causing structural damage to the home. It can also leak and cause mold and water damage. And to avoid further complications, always follow local zoning ordinances, building codes, and HOA regulations.

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