How To Figure Roof Rafters

Calculate the length of a rafter from the roof slope ratio of inches per foot and a building width measurement.

How to figure roof rafters.

Rafter length using pitch v r 2 sqrt 1 p 2 where v overhang r roof span p pitch. Refer to the. 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. Determine the pitch of the roof which is the angle that rafters rise from the outside walls to the ridge.

The other thing you ll need is the roof pitch angle. I prefer using the right hand. Roof pitch calculator. 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.

You might need a long tape measure to get the span then. Total span ridge 2 individual rafter span. Laying out a calculated rafter place the board on a set of sawhorses with the crown away from you. How to calculate rafter lengths step 1.

Use a framing square to mark a plumb cut as close to the end of the board as possible. Each common rafter span is calculated by subtracting the thickness of the ridge from the total span then dividing the answer by two. Determine the direction the rafters rise from opposite outside walls to the ridge. Hook the long point with a tape measure stretch it out past the length and make.

Rise and run means that a 6 12 pitch roof has 6 of rise vertical for each foot of run horizontal.