Roof Frame Span

03 01 2014 page 1 of 2 8 9 footnotes.

Roof frame span.

Rafter and joist span faq. Refer to the figure as you study the terms discussed in the next paragraphs. Unit of run is a fixed unit of measure always 12 inches for the common rafter. The typical thickness range for sheathing is 3 8 to 3 4 inch.

Visit the roof framing page for more information on cutting roof rafters and visit the roof pitch calculator for determining rafter lengths based on rise and run. 1 used under dry conditions with lumber moisture co ntent less than 16 percent at time of installation. Span calculator for wood joists and rafters also available for the android os. Never attach roof sheathing with staples.

So this table could accommodate a house with a total rafter span or house width of 32 feet. The lengths and sizes of joists vary depending on the species and quality of the lumber used. Span tables building division 5510 overland ave suite 110 san diego ca 92123 858 565 5920 888 336 7553 http www sdcpds org pds 415 rev. 8d ring shank nails should be used instead.

For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements. The tables below give maximum spans for rafters and beams. As a general rule roofs that have a high human occupancy rate should be framed with rafters every 16 structures such as sheds or barns can be frames with rafters every 24 again make sure to consult local codes. For example in the rafter span table below the highlighted cell in the 40 live load table indicates that 2 x 8 southern yellow pine joists that have a grade of 2 that are spaced 24 apart can have a maximum span of 10 feet 3 inches 10 3 if designing for a live load of 40 lbs ft 2.

In areas with mild climates patio roofs are generally designed for loads of 30 psf pounds per square foot. Span is the horizontal distance between the outside top plates or the base of two abutting right triangles. Also available for the android os. The spans in this table are based on a maximum supported rafter span of 16 feet where the supported span is the total horizontal distance spanned by the roof rafters divided in half not the diagonal distance or the length of the rafter.

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. Roof sheathing comes in grid marked 4 by 8 foot sheets and should be installed perpendicular to the frame. Features associated with basic roof framing terms are shown in figure 2 2. Maximum rafter spans for a patio roof.