Floor Joist Design

Maximum floor joist span for no.

Floor joist design.

I joists have major advantages in high volume construction with standard layouts. Floor joists should be spaced no more than 16 inches 41 cm apart from center to center to provide adequate stability. Wood i joists with dimension lumber top and bottom chords and osb web. The design and construction of ceiling joists are found in section r802 4 of the irc.

2 grade of douglas fir are indicated below. Some newer homes have manufactured i beam shaped joists. The floor joist spacing is the distance between the centers of any two installed joists. Don vandervort hometips.

True floor joist span calculations can only be made by a structural engineer or contractor. In this post we will cover wood roof framing members specifically ceiling 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. Live load is weight of furniture wind snow and more.

Open web trusses with wood webbing held together with metal plates. The table references have changed in the 2018 version of the irc. Span calculator for wood joists and rafters also available for the android os. The allowable ceiling joist span tables in the 2018 version are found in section r802 5.

Floor joists are typically 2 by 8s 2 by 10s or 2 by 12s. 1 psf lb f ft 2 47 88 n m 2. Mark the position of each floor joist along the sill plate. Two types of engineered joists are most frequently used in floor systems today.

See the image below for an example of joists spaced 16 on center 16 o c. 1 ft 0 3048 m. Use a tape measure to measure 16 inches 41 cm in from the edge of the rim joist and draw a small notch. Ceiling joists are usually 2 by 6s or sometimes 2 by 4s if it is an older home.

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.