How To Size A Roof Rafter

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.

How to size a roof rafter.

If you look at the rafter span chart you ll notice that 2x4s can be used for rafters on spans up to 11. Measure the width of your building. If your project had a rafter length of 8 or less a safe and strong method is to use 2x8 framed 16 on center. Input the rafter span on the flat eave overhang and pitch of the roof.

Divide the adjusted width. Anything beyond that you are looking at using 2x6s for most sheds. This calculator is to be used as an estimating tool only. 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.

Calculating rafter length 1. The ridge beam is the vertical piece of plywood which will form the peak of. Includes result for hip valley factor slope factor and the roof slope in degrees. 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.

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 length using angle v r 2cos a rafter length using pitch v r 2 sqrt 1 p 2 where v overhang r roof span p pitch use our online rafter length calculator to quickly compute the length of the shed roof rafter by entering the measurements of overhead length of roof span pitch or angle. Rafter stock size calculator. Click the button to calculate the stock size needed for this job.

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. Rise and run means that a 6 12 pitch roof has 6 of rise vertical for each foot of run horizontal. Subtract the width of your ridge beam. Input the rafter span on the flat eave overhang and pitch of the roof.

Click the button to calculate the stock size needed for this job. If you add an eaves overhang dimension then the amount the rafter sticks passed the wall will be added to the rafter length. Roof rise this should be calculated from the base of the roof to the highest point of the roof gable the peak. Calculate the length of a rafter from the roof slope ratio of inches per foot and a building width measurement.

Here the number is 1166 66 inches. Here the number is 941 86 inches. Before you start cutting you first need to determine how long your roof rafters.