Floor Joist And Beam

Floor joists or beams provide the below surface support for the wood subfloor of a room.

Floor joist and beam. Floor joists rest directly on beams. Walls and columns often sit on floors so they may rest indirectly on beams. The supported length shown along the left most side of the table is the total length of the floor joists to be supported on either side of the floor beam divided by two. I joists provide a high performance alternative to dimension lumber joists for floor and roof applications.

You can also use the wood beam calculator from the american wood council website to determine maximum rafter and joist lengths. In the case of our example house the house is 24 feet wide so the house will require a total width of 24 feet of joists. Joists and beams are two types of structural elements that have similar and related functions in home construction. Both are horizontal members meaning they are installed level with the ground or floor below and both are supported on their ends and sometimes in their middles by load bearing walls columns or other types of vertical supports.

These are the right choice for both residential and non residential floor and roof joist construction. Beams are large few in number and supported by a foundation posts or a wall. This sample table gives minimum floor joist sizes for joists spaced at 16 inches and 24 inches on center o c for 2 grade lumber with 10 pounds per square foot of dead load and 40 pounds of live load which is typical of normal residential construction. A joist is a horizontal structural member used in framing to span an open space often between beams that subsequently transfer loads to vertical members.

When incorporated into a floor framing system joists serve to provide stiffness to the subfloor sheathing allowing it to function as a horizontal diaphragm. Joists are small numerous and supported by a beam. Though joists may be any size that you desire using typical floor joist and beam specifications ensures that you can find hardware to fit the joists and that the floor provides adequate support for furniture and other items in a room. True floor joist span calculations can only be made by a structural engineer or contractor.

Beams are large horizontal members that carry the floor loads from the floors walls or roofs to the columns or foundation walls. Use the span tables below to determine allowable lengths of joists and rafters based on size and standard design loads. Dividing by two gives us 12 feet of supported length.