There are three main ways to add onto a house:
Building Out: The vast majority of additions involve increasing the footprint of the ground-floor level of the building. That’s largely because so many additions are first-floor additions — whether you’re expanding the kitchen, adding a family room, or simply live in a one-story home.
Additions should be placed to the rear of a building wherever possible. An extension along existing building lines toward the rear usually does not require a zoning variance, though it could if too much of the lot area is covered by the building.
- Pros: Building out typically involves the least disruption to the existing space and to your life if you’re living at home through the project because you’re not supporting the new space over the existing structural framing or foundation.
- Cons: Building out means losing some of your yard, and might even require a zoning variance from the town if you’re within the legal property line “setback” from the neighbor’s property.
There are many ways that additions can happen without expanding the footprint of the house: You can add another story onto a one-story home. You can expand an existing top floor by installing large dormers in a pitched roof to gain useful living space. Or you might add living space above an existing garage, porch or other one-story wing.
The stair is the one element that connects two levels together and it becomes an opportunity to create a dramatic space. Consider adding skylights at the top of the stairs so light floods down through to lower levels.
- Pros: You won’t lose any yard nor bump into zoning restrictions about setbacks or floor-area-ratio limits.
- Cons: Many towns limit the allowable height for houses, which can be an issue when building up.
Bump out: A “bump-out addition” A bump-out can be a cost- effective way to open up the space in an existing room, making it feel larger, allowing in more light or even adding access to the outside. The entire flow of a space can be changed with a simple bump-out.
That may be enough to add an eating area to your kitchen or a separate tub and shower to your master bathroom.