Pitched Roof Rafter Sizes

4 8 2 2 4 for one half of your roof s width b skip this step if you already know what measurement half the width of your roof is.

Pitched roof rafter sizes. To establish the rafter length we calculate the following. Roof pitch between 15 and 22 5 degrees with rafter this diagram illustrates the typical arrangement of a rafter and purlin roof and shows the dimensions referred. Surveyors span tables for designing roof rafters. The pitch and span of your roof will dictate how long of a rafter you ll need use maximum span calculator to help you find your rafter size.

2 4 x 1 1034 refer to image to the right. If you look at the rafter span chart you ll notice that 2x4s can be used for rafters on spans up to 11. All the figures are based on roofing tiles or slates laid on timber laths over sarking felt. The roof pitch should be specified on your technical drawings for the job along with the sizes of the roof timbers.

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. The following tables give details of the allowable spans and spacing for some of the more common timber sizes used in traditional roofing construction. If you are deciding yourself on the pitch make sure it is suitable for your roof covering. 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.

The other thing you ll need is the roof pitch angle. 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. Weather you re building a shed roof or adding a dormer to your second story it is important to choose the proper size rafter. Rise and run means that a 6 12 pitch roof has 6 of rise vertical for each foot of run horizontal.

In this example we have a customer with a building width of 4 8m wide and the pitch of the roof is 25. The following tables give details of the allowable spans and spacing for some of the more common timber sizes used in traditional roofing construction. Total span ridge 2 individual rafter span. Pitched roof timber sizes 1.

There are several variables to consider when determining the proper rafter size. Rafter span tables for surveyors roof construction. 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.