Floor Joist Board Size

This size is no longer acceptable when framing a structure.

Floor joist board size. 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. 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. 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. Looking at this table you will see there is a choice in the size of floor joist 2 x 6 2 x 8 2 x 10 or 2 x 12 and there is a choice in the joist spacing 12 16 or 14.

The width is considerably more important than the thickness of a board. 1 psf lb f ft 2 47 88 n m 2. 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. The strength of a given joist board is most dramatically affected by the board s top to bottom width.

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 the past 2x4s or 2x6s were sometimes used as floor joists. Joist span and spacing is set by your local building code. The larger the deck the larger the joists.

The exact size necessary may be stipulated by the building code required for a particular structure. Live load is weight of furniture wind snow and more. 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. 2x10 to 15 feet and 2x12 to 18 feet.

In joist sizes the larger size such as 6 inches represents the height of the joists while the 2 inch size represents the. Dead load weight of structure and fixed loads 10 lbs ft 2. 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. 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.

Common joist spacings are 12 inches 304 8 mm 16 inches 406 4 mm and 24 inches 609 6 mm. 2 grade of douglas fir are indicated below. A 2x8 up to 12 feet. 1 ft 0 3048 m.

Maximum floor joist span for no. 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. In general practice 2x8s 2x10s or 2x12s are used when framing a raised floor instead.