Design Timber Floor Joists

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.

Design timber floor joists.

Live load is weight of furniture wind snow and more. True floor joist span calculations can only be made by a structural engineer or contractor. 2 grade of douglas fir are indicated below. 1 psf lb f ft 2 47 88 n m 2.

Dead load weight of structure and fixed loads 10 lbs ft 2. As an example consider a room with a floor area of 10 feet by 11 feet 2 inches built with no. Apa performance rated i joists pris are manufactured in accordance with pri 400 performance standard for apa ews i joists form x720 this performance standard provides an easy to use table of allowable spans for applications in residential floor construction allowing designers and builders to select and use i joists from various member manufacturers using just one set of span. The allowable clear spans have been calculated in accordance with bs 5268 2 2002 structural use of timber part 2.

See the image below for an example of joists spaced 16 on center 16 o c. Code of practice for permissible stress design materials and workmanship and bs 5268 7 1 1990 structural use of timber section 7 1 domestic floor joists. A design value table shows that the joists have an fb value of 1 495 and an e value of 1 900 000. Since the example house we are designing for is 12 feet wide we need to find in the floor joist span table a joist size and centering that can span 12 or wider.

Maximum floor joist span for no. 1 ft 0 3048 m.