Roof Rafter Sizes For Pitched Roof

The length of rafter per meter of run is 1 1543.

Roof rafter sizes for pitched roof.

Here the number is 941 86 inches. This means that for every 1m the rafter travels horizontally the angled length of the roof will be 1 1543m. For pitched roofs flat roofs and ceiling joists. It is always better to have a large rafter rather than be concerned with a sagging roof.

Usually 400 450 or 600mm but any value can be used up to 610mm max usually 400 450 or 600mm but any value can be used up to 610mm max are there any brittle finishes e g. Plasterboard on the underside of the rafter. Surveyors span tables for designing roof rafters. 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.

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 is the distance between rafter centres. Here the number is 1166 66 inches. 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.

Roof rise this should be calculated from the base of the roof to the highest point of the roof gable the peak. All we do now is use a calculator to multiply 1 610 by the measurement in the book. If your project had a rafter length of 8 or less a safe and strong method is to use 2x8 framed 16 on center.