What Size Beams Are in an A-Frame House?

Variables

• When choosing a beam size for your A-frame, use an architectural program or hire an architect to draw up plans. There are too many variables to be very accurate on beam size for any A-frame house. Even a small amount of snow can alter load bearing requirements for the structure. The size of the house, the shape of the walls and number of rooms, among many other details, will all control how large the beams in the house need to be. Even the type of wood used has its effect. Professional sizing charts and weight bearing calculations, as well as consultation of local codes, is vital.

Built-Up Beams

• Built-up beams are roof beams used to support the roof rafters, both important components in the roof-dominated A-frame construction. For many beams, 2-by-8-inches or 2-by-10-inches is a common size, although 2-by-12-inches may also be used. Extra blocking may be necessary depending on the length of spans. These beams are very helpful when constructing an A-frame house, because they allow for structural posts to support roof beams instead of a problematic continuous beam.

Rafters

• Roof rafters tend to fall in customary sizes such as 2-by-6-inch, 2-by-8-inch, 2-by-10-inch or 2-by-12-inch. Not all these sizes are used at the same time, of course. The maximum span of the rafters depends on how they are spaced out across the roof. The maximum span for a two-by-six with spacing of 12 inches between rafters is 14.9 inches. The maximum span goes down as spacing increases, but goes up as rafter size increases.

Joists

• Joists are the key beams that run across floors in homes and basic support between larger bracing beams, especially for second stories. Joists range from 2-by-4-inches to 2-by-12-inches, depending on the type of floor and construction. Studs, the equivalent type of beam in the wall, also tend to be either 2-by-4-inches or 2-by-6-inches, depending on construction.