How To Figure Roof Rafters

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.

How to figure roof rafters.

Rise and run means that a 6 12 pitch roof has 6 of rise vertical for each foot of run horizontal. 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. Typically this is shown on. Determine the pitch of the roof which is the angle that rafters rise from the outside walls to the ridge.

Laying out a calculated rafter place the board on a set of sawhorses with the crown away from you. Use a framing square to mark a plumb cut as close to the end of the board as possible. Total span ridge 2 individual rafter span. Rafter length using pitch v r 2 sqrt 1 p 2 where v overhang r roof span p pitch.

How to calculate rafter lengths step 1. Hook the long point with a tape measure stretch it out past the length and make. Includes result for hip valley factor slope factor and the roof slope in degrees. If you add an eaves overhang dimension then the amount the rafter sticks passed the wall will be added to the rafter length.

Calculate the length of a rafter from the roof slope ratio of inches per foot and a building width measurement. Refer to the. Roof pitch calculator. You might need a long tape measure to get the span then.

Determine the direction the rafters rise from opposite outside walls to the ridge.