Roof Frame Span

Span is the horizontal distance between the outside top plates or the base of two abutting right triangles.

Roof frame span.

1 used under dry conditions with lumber moisture co ntent less than 16 percent at time of installation. The tables below give maximum spans for rafters and beams. Span calculator for wood joists and rafters also available for the android os. The lengths and sizes of joists vary depending on the species and quality of the lumber used.

03 01 2014 page 1 of 2 8 9 footnotes. Sheathing should be a minimum of 19 32 inch thick. Rafter and joist span faq. 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.

Roof sheathing comes in grid marked 4 by 8 foot sheets and should be installed perpendicular to the frame. Refer to the figure as you study the terms discussed in the next paragraphs. 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. In areas with mild climates patio roofs are generally designed for loads of 30 psf pounds per square foot.

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. The typical thickness range for sheathing is 3 8 to 3 4 inch. Designing with roof rafter span tables roof framing learn how to frame a load power beam anthony forest s cotimber steel framing manual single span ridge beamglulam ridge beam span table elcho. 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 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. 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. 8d ring shank nails should be used instead. Unit of run is a fixed unit of measure always 12 inches for the common rafter.

Also available for the android os. Maximum rafter spans for a patio roof. For heavy roofs or in areas with substantial snowfall or winds call your local building department for code requirements. Never attach roof sheathing with staples.