How to calculate rafter lengths step 1.
How to figure roof rafters.
Determine the direction the rafters rise from opposite outside walls to the ridge.
I prefer using the right hand.
Roof pitch calculator.
Includes result for hip valley factor slope factor and the roof slope in degrees.
Calculate the length of a rafter from the roof slope ratio of inches per foot and a building width measurement.
If you add an eaves overhang dimension then the amount the rafter sticks passed the wall will be added to the rafter length.
Laying out a calculated rafter place the board on a set of sawhorses with the crown away from you.
Total span ridge 2 individual rafter span.
Determine the pitch of the roof which is the angle that rafters rise from the outside walls to the ridge.
Rise and run means that a 6 12 pitch roof has 6 of rise vertical for each foot of run horizontal.
The other thing you ll need is the roof pitch angle.
Use a framing square to mark a plumb cut as close to the end of the board as possible.
You might need a long tape measure to get the span then.
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.
Each common rafter span is calculated by subtracting the thickness of the ridge from the total span then dividing the answer by two.
Typically this is shown on.
Hook the long point with a tape measure stretch it out past the length and make.