Find the unit rise say inches per foot of the roof on the top line in the framing square rafter table e g.
How to figure roof pitch with a framing square.
This article explains how to make quick use of a framing square and its imprinted data to get some basic roof measurement data like roof pitch or slope rafter lengths and end cuts.
The hash marks with corresponding numbers between 1 and 30 refer to the roof s rise angle.
The pitch of the roof is read where the bottom of the rafter crosses this scale.
8 inches and you have an 8 in 12 pitch.
Directly below the 6 inch mark on the framing square read the required rafter length 13 42 per foot of run for a 6 inch rise 6 in 12 roof.
If this distance measures 4 inches you have a 4 in 12 pitch.
A 6 inch rise per foot.
Read this number along the inches scale at the top of the framing square.
Pitch measurement method 1.
On a ladder beside the roof place the level a foot or so up the roof hold it level and measure from the 12 inch mark on the level s bottom straight down to the roof.