Floor Joist And Beam

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.

Floor joist and beam.

These are the right choice for both residential and non residential floor and roof joist construction. True floor joist span calculations can only be made by a structural engineer or contractor. I joists provide a high performance alternative to dimension lumber joists for floor and roof applications. 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.

Dividing by two gives us 12 feet of supported length. 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. Walls and columns often sit on floors so they may rest indirectly on beams. Joists and beams have many similarities but they differ in size and the role they play.

Beams are large horizontal members that carry the floor loads from the floors walls or roofs to the columns or foundation walls. Joists the horizontal members that span two walls and or beams have to carry the weight of the walls people furniture appliances and other stuff we place on them. Floor joists rest directly on beams. 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.

You can also use the wood beam calculator from the american wood council website to determine maximum rafter and joist lengths. When a load is applied to a joist the wood fibers along the bottom edge go into tension and those along the top go into compression fig. Floor joists or beams provide the below surface support for the wood subfloor of a room. Use the span tables below to determine allowable lengths of joists and rafters based on size and standard design loads.

Beams are large few in number and supported by a foundation posts or a wall. 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.