Floor Joist And Beam Design

In the table above the widest floor beam span for 12 of supported floor joists is 14 7 if using a 5 ply 2 x 12.

Floor joist and beam design.

Floor joists or beams provide the below surface support for the wood subfloor of a room. View joist rafter tables. Use the span tables below to determine allowable lengths of joists and rafters based on size and standard design loads. Both stretch across long spans.

Technically joists are a type of beam. Our floor joist beam can span a maximum of 13. Another way to say that beams and joists hold up weight pushing down along the long straight side. 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.

So we now have adequately sized floor joists and an adequately sized floor joist beam for our 24 x 13 house. Simplified maximum span tables for selected visual and mechanical grades of southern pine lumber in sizes 2 4 thru 2 12. 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. Size members for a specific spacing depth or the best economical fit.

Both the 2009 irc and the dca6 09 allow 2 southern pine 2x10s to span 13 feet 1 inch at 24 inches on center at a design load of 50 psf. Nine joists will be needed for the 16 foot width. That means these joists can span the 12 foot depth of the deck and the beam can be located at the perimeter. The load carried by joists and beams is applied at a right angle to the length of the span.

Therefore joists may run from wall to wall wall to beam or beam to beam depending on the size of the area they span and the structural design of the home. That is beams and joists are building parts that lay flat rather than stand up. Click here for background information regarding design values. True floor joist span calculations can only be made by a structural engineer or contractor.

The joists span across a room or other area are supported on their ends and sometimes in their middles by load bearing walls or beams.