Beam Size If Attic Above

They transfer loads from above to the foundation below through a network of structural elements.

Beam size if attic above.

The formula for the section modulus is beam width times beam depth squared divided by 6. Fine homebuilding notes that 2 inch by 6 inch garage joists will support a weight of up to 50 pounds per square foot. Although you can construct a garage using thicker stronger joists 2 inch by 6 inch joists are sufficient for most garages even if you intend to build an attic storage area above your garage. These nine beam spans are for built up beams made up of either 2x8 2x10 or 2x12 dimensional lumber nailed together as either 3 4 or 5 ply beams.

Tables providing size selections for various beam spans and loading combinations for southern pine dimension lumber and southern pine glued laminated timber are available for the following applications. Anything 5 and above we always at least double cripple. On longer spans the beam may require much more bearing space as indicated by this table. Add together all live loads and dead loads that act on the member and then choose a material that will resist the load.

According to the 2012 irc codes any beam joist or header shall never have a bearing of less than 1 1 2. A two 2 by 6 standard beam has actual dimensions of 1 5 by 5 5 inches which would give a section modulus of 1 5 x 5 5 x 5 5 6 7 6 which is not enough for this example. For example a 3 ply 2x8 beam would use three 2x8s nailed together side by side. Two 2 by 4 beams together would not be enough.

The idea behind sizing headers and beams is straight forward. The job of headers and beams is a simple one. A 2 by 8 beam would be sufficient.