- 1). Layout the board on a set of saw horses and figure out the crown of the board, the crown needs to be up [or the crown is the top of the rafter where the would sheeting nails to} Lets say that the roof is a 12-pitch and the rafter length to the heel height [or A-1 in drawing] is 90", the overhang [or C-1] is 12", the Rafter Tail measurement [or A-2] 17",
- 2). Understanding heel height [B-1][our example height is standard 3-1/2"], if you already have that measurement figured out and or understand what its for your all set on this step. If not here are a few key things to think about when figuring out a new heel height. The heel height will not change your rafter measurement, Its does move the vertical measurement of where the top ridge board will go and the height of where the overhangs/fascia nails on the side walls.
- 3). After all your measurements are ready, [we are using the ones in the example] the first mark to make is [A-1] our is 90" that mark would be from "Long To Short of a 12-pitch" with a line marking the angle on the board. [long to short is when the angle is going the same way] Using the 12-pitch line in the center for heel height [or {B-1}] put the measuring square on the [B-1] mark the same way you did when making the mark then measure down the heel height [3-1/2"], From that mark lay the measuring square on the board this time lining it up with your line and the heel height measurement so the you can get a square line coming off the 12-pitch angle line made for [B-1]. Next measure out the Tail measurement [or A-2] marking a line on a 12-pitch angle the same as the first [A-1] marks that was made. Last is [D-1] the layout/cut made so the [standard 2x6] fascia boards are flush with rafters. The easiest way to do this is to set a small peace of whatever your using for fascia on plane with the top of the rafter so that the top edges stay on roof plane then mark the bottom edge.
- 4). Cutting the Rafter, Very simple just cut the lines for the most part just be very careful when cutting out the heel height into the rafters.
Source...