Roof Rafter Dimensions

Weather you re building a shed roof or adding a dormer to your second story it is important to choose the proper size rafter.

Roof rafter dimensions.

To cut roof rafters start by fixing the stair gauges on your framing square to the dimensions of your pitch. Rise and run means that a 6 12 pitch roof has 6 of rise vertical for each foot of run horizontal. 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. Rafter span tables use these tables to determine lengths sizes and spacing of rafters based on a variety of factors such as species load grade spacing and pitch.

Usually 400 450 or 600mm but any value can be used up to 610mm max. Roof rise this should be calculated from the base of the roof to the highest point of the roof gable the peak. For example if the roof rises 4 feet and the span is 16 feet twice the run then the pitch is 4 16 or 1 4. The rafter member will be longer.

Are there any brittle finishes e g. Half building width minus 1 2 ridge thickness. Here the number is 941 86 inches. See rafter run to outer wall calculator below.

There are several variables to consider when determining the proper rafter size. This diagram illustrates the typical arrangement of a rafter and purlin roof and shows the dimensions referred to in the tables above. It is the length of this portion of the rafter. Find its length with our online rafter length calculator.

Once you ve marked the lines use your pencil to draw the diagonal length on the rafter. 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. Allow for ridge thickness when determining rafter run to outer wall. A useful shed roof rafter calculator to calculate the rafter length for the given dimensions of the roof of the building or a structure.

Our roof rafter calculator tools are handy for calculating the number of rafters needed rafter length calculator lineal feet of rafter board feed in ridge and sub facia and the total board feet in the roof. If you plan to have overhang etc. Rafter is the beam supporting the building. This is the distance between rafter centres.

Next set the framing square on top of the rafter beam and use a pencil to trace the outside edge of the framing square s tongue. Plasterboard on the underside of the rafter. Imposed loads roof snow load and short term point load. Here the number is 1166 66 inches.

This sizing guide for roof rafters will help determine what you need for your small project.