How To Figure Roof Rafters

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

How to figure roof rafters.

Total span ridge 2 individual rafter span. 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. Includes result for hip valley factor slope factor and the roof slope in degrees. Rafter length using pitch v r 2 sqrt 1 p 2 where v overhang r roof span p pitch.

Use a framing square to mark a plumb cut as close to the end of the board as possible. Calculate the length of a rafter from the roof slope ratio of inches per foot and a building width measurement. The other thing you ll need is the roof pitch angle. I prefer using the right hand.

Typically this is shown on. How to calculate rafter lengths step 1. Hook the long point with a tape measure stretch it out past the length and make. Laying out a calculated rafter place the board on a set of sawhorses with the crown away from you.

Determine the pitch of the roof which is the angle that rafters rise from the outside walls to the ridge. 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. Rise and run means that a 6 12 pitch roof has 6 of rise vertical for each foot of run horizontal. Each common rafter span is calculated by subtracting the thickness of the ridge from the total span then dividing the answer by two.

You might need a long tape measure to get the span then.