Floor Joist Board Size

1 ft 0 3048 m.

Floor joist board size.

For example if you double the thickness or number of joists in a floor the distance the boards can span will increase by approximately 25. See the image below for an example of joists spaced 16 on center 16 o c. Maximum floor joist span for no. Choosing the correct floor joist size depends on your building application joist spacing and several other factors these include the length of the span as well as the type and grade of the lumber being used.

Joist span and spacing is set by your local building code. The floor joist spacing is the distance between the centers of any two installed joists. Common joist spacings are 12 inches 304 8 mm 16 inches 406 4 mm and 24 inches 609 6 mm. While most residential construction uses 2x8 joists with 16 inch spacing there are many other factors you need to consider when determining the proper joist span length.

A 2x8 up to 12 feet. In the past 2x4s or 2x6s were sometimes used as floor joists. The width is considerably more important than the thickness of a board. 2x10 to 15 feet and 2x12 to 18 feet.

Dead load weight of structure and fixed loads 10 lbs ft 2. In general practice 2x8s 2x10s or 2x12s are used when framing a raised floor instead. The wood boards used as floor joists generally range in size from no smaller than 2 by 4 inches to no larger than 2 by 12 inches. Two by 6 inches is a joist size frequently used in both indoor floors and as deck joists.

The exact size necessary may be stipulated by the building code required for a particular structure. In typical deck construction with a ledger on one side of the joist and beam on the other the size of the joists is driven by the size of the deck and based on the general maximum spans mentioned above. 1 psf lb f ft 2 47 88 n m 2. This size is no longer acceptable when framing a structure.

Floor joists are made from 2 by 8 inch or 2 by 10 inch lumber or from engineered quiet beams which are made from a thin layer of chipboard on edge between two lumber caps forming an i shape. 2 grade of douglas fir are indicated below. Live load is weight of furniture wind snow and more. The width of a board is an important factor in determining the distance a floor joist can span playing a much larger role than the thickness.

In joist sizes the larger size such as 6 inches represents the height of the joists while the 2 inch size represents the. For example a joist made from doubled 2 x 6s can span a distance about 25 percent more than a single 2 x 6 but a 2 x 12 can span about 80 percent more than. When building a house or even a deck it is important to confirm you have the correct joist sizes spans and spacing before you get started.