Structural Solutions for Small Bump-outs
With the right support, foundation-free additions can make a big impact.
Synopsis: Bumping out is a great way to expand a living space without putting a full addition on your home. Managing editor Debra Silber offers a survey of six examples of successful bump-outs that added value without a great deal of stress. These bump-out solutions include projects supported by boxes, brackets, and cantilevers, and the rooms added to include a bathroom, a dining room, and a kitchen.
Sometimes you don’t need an entire room to make a floor plan work. Sometimes all you need is a few feet. But sometimes you’re in a situation where adding a few feet to a home’s footprint will throw off its style, crank up project costs, or put the owners on the wrong side of local zoning rules. In these cases, a small, self-supporting addition — a bump-out — can be the answer.
But it’s an answer that immediately raises another question: If an addition won’t be supported from underneath, how will it be held up?
Here, we explore some of the structural options for bump-out additions, defined for our purposes as structures that extend a room by no more than 4 ft. and do so without significant ground contact outside the original footprint. The examples that follow run the gamut from bench-seat projections to floor-level extensions, and their support structures vary from grounded brackets to cantilevered floor joists. All deal with real-world restrictions, and none is without its own challenges that manage to remake this simple answer into a lesson in creative construction.
While there are some structural rules of thumb for cantilevers, brackets, and the other solutions found here, every situation is unique. It’s always best to consult an engineer on any structure of this type, as the builders and architects featured here did on their projects.