Roof Joist Sizes And Spans

These spans were calculated using our flat roof joist calculation engine.

Roof joist sizes and spans.

Although 2 x 4 s are included in the official table they are not listed because it is never advised to use them. These span tables are the equivalent of other industry standard span tables and are calculated to the same standards. This span table is to the format and methodology given in bs 5268 7 2. Select the appropriate table in span tables for joists and rafters.

Step 2 span table. Spans of timber joists in suspended timber ground floors span tables. The lengths and sizes of joists vary depending on the species and quality of the lumber used. 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.

Rafter and joist span faq. Joist span and spacing is set by your local building code. For floor and ceiling construction surveyors can calculate the size strength and centres spacing of joists with reference to the data in these tables. 2 x 12 s are not listed because you can span pretty much whatever you want.

It covers 2 common lumber species and sizes at 20 pounds per square foot load. View joist rafter tables. Joists rafters simplified maximum span tables for selected visual and mechanical grades of southern pine lumber in sizes 2 4 thru 2 12. The range of joist sizes used in homes varies though between 2 by 4 inches and 2 by 12 inches.

For example you can span a 1 grade no knots southern yellow pine a greater distance than a 2 grade with knots southern yellow pine. Surveyors span tables for designing roof rafters. 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. Listed are 46 tables based on common loading conditions for floor joists ceiling joists and rafters.

Click on a span to generate a full calculation you can adjust the exact span. 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. Using table f 2 figure 3 check each lumber size to see if a 16 inch spacing will permit a span of 15 feet 1 inch. The table of contents indicates that table f 2 watches these loading conditions.

Surveyors and structural engineers utilise data from tables below to help calculate the correct size strength and centres of roof timbers for the required spans and loadings. This ceiling joist span table is based on the 2012 irc for uninhabitable attics with limited storage.