Extend a Room:
Bumpout, Build-out or Dormer?
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Your house is perfect except that you just need a little more space in the living room, kitchen, bathroom or dining room.
An economical option is to extend a room, rather than add-on. Three alternatives to extending a room are: a bumpout (cantilever extension), a larger build-out, or a dormer on the second storey.
A great option if you only require a little more space for a kitchen pantry, corner bathtub, office space or closet, but can't fit it into your existing structure.
The maximum extension of a bumpout depends on the floor joist size and the species of lumber. A general rule of thumb for construction grade spruce:
16" max cantilever for 2x8 floor joists
Check your local building code
24" max cantilever for 2x10 floor joists
to determine the maximum size that you can extend a room.
To significantly extend a room size, a build-out may be the answer.
For a 1st storey build-out, you can use either posts and footings for support, stacked concrete blocks, or poured concrete.
For a 2nd storey build-out, you must use posts and footings for support. You can combine a build-out with a porch underneath to increase the outdoor living space and make your home more attractive.
Consult your local build code to determine the structural requirements.
For gable or sloping roofs, a dormer can add character to your home, not to mention increase the size of a bedroom, bathroom, sunroom, stair landing, office or create an alcove.
The maximum dormer size is determined by the strength and size of the existing framing in your home. You may have to increase the size of your existing posts, beams and joists if you have a dormer that is larger than what your home can support.
Check your local building code and consult with an experienced builder or structural engineer to determine the appropriate dormer size and roof slope.
When you extend a room, you should pay close attention to the architectural details so that the new extension fits in with the style of your home.
For some great examples of well-designed additions, see curb appeal. You can also review the architectural style of your home.