Roof Rafter Sizes For Pitched Roof

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.

Roof rafter sizes for pitched roof.

Plasterboard on the underside of the rafter. 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. It is always better to have a large rafter rather than be concerned with a sagging roof. The length of rafter per meter of run is 1 1543.

Here the number is 1166 66 inches. For pitched roofs flat roofs and ceiling joists. This means that for every 1m the rafter travels horizontally the angled length of the roof will be 1 1543m. 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.

Surveyors span tables for designing roof rafters. Here the number is 941 86 inches. Again make sure to consult local codes. 1 1543 x 1 610 1 858m.

All we do now is use a calculator to multiply 1 610 by the measurement in the book. This is the distance between rafter centres. Rafter run outer wall this should be measured starting from the center of the roof span and then extending to the very edge of the exterior wall.