Floor Joist Design Example

Design of 3 3x12 timber beam with southern pine solved example.

Floor joist design example.

Ce 331 spring 2002 joist and frame design example 1 2 1. A floor joist appropriately selected to span 10 feet with an l 360 limit will deflect no more than 120 360 1 3 inches under maximum design loads. Drywall attached to the underside of this system is not expected to crack when the floor joist system deflects 1 3. But larger is not always better when builders are constructing a home or adding a room addition.

See the image below for an example of joists spaced 16 on center 16 o c. The extra two inches of vertical distance when a floor is framed with 2 x 10 joists rather than 2 x 12s can be quite important for example. Calculate the dead load on a typical purlin. Common sense tells you that large floor joists can carry more load and spacing joists closer together also increases the load bearing capacity of a floor.

Design a typical floor joist for the two story office building indicated below. The floor joist spacing is the distance between the centers of any two installed joists. 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. Draw the purlin and show the dead loading.