Roof Joists Width

Spacing in exterior exposure.

Roof joists width.

Weather you re building a shed roof or adding a dormer to your second story it is important to choose the proper size rafter. Let s consider a basic gable wood roof framing design. For example the highlighted cell below shows that a 2 x 6 southern yellow pine joist with a grade of 2 and spaced 24 apart can have a maximum span of 10 feet 0 inches 10 0 if you are designing your structure to support a plaster ceiling. Here we have a wood framed gable roof.

Decreasing the distance between rafters to 12 inches however increases the maximum span to 14 feet 4 inches. This sizing guide for roof rafters will help determine what you need for your small project. Floor joist span use this table to determine the maximum lengths of floor joists based on species of lumber joist spacing and joist size. Span calculator for wood joists and rafters also available for the.

Joist span and spacing is set by your local building code. Standard size of joists though there is no standard joist size for the ceilings in all buildings most average homes use ceiling joists in a board size of 2 by 6 inches. Various lumber size options 2 4 2 6 2 8 2 10 the maximum ceiling joist span based on the lumber size species grade and spacing used. Ceiling joist spacing in inches 12 16 19 2 24 species and grade of lumber.

Continuing on from part 3. In other words you would space a roof joist 15 inches apart from another roof joist but never 17 inches apart. There are several variables to consider when determining the proper rafter size. Live load psf dead load psf span calculator for wood joists and rafters available for the iphone.

If the roof is not completely square you can decrease the space between joists but never increase the space. 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. Ceiling joist span use this table to determine the maximum lengths of ceiling joists based on species of lumber joist spacing and joist size. For example 2 by 6 rafters made from select structural grade douglas fir that are required to support a live load of 20 pounds per square inch can have a maximum horizontal span of 11 feet 4 inches.

The range of joist sizes used in homes varies though between 2 by 4 inches and 2 by 12 inches. A roof joist is always spaced no more than 16 inches apart from another roof joist. Now in order to correctly size ceiling joists lets take a look at a few examples.