Valley rafter layout – Johnson Level & Tool Mfg. RAS-1 User Manual

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Now mark across top of ridge (as shown). This mark will be

the center of the two intersecting hips. If a common rafter

is to be used, the ridge will be cut off at this mark and the

common rafter butted up against it (see Figure 9). If no

common rafter will be used, cut the ridge about 2" longer.

This will allow you to nail through the ridge into the hip.

VALLEY RAFTER LAYOUT

STEP 1. TOP PLUMB CUT: Using the Hip-Val scale again,

make the top plumb mark in the usual way. Now measure

down the top of the rafter from this mark for a miter allow-

ance, if used (see Figures 12 and 13). Look up the allowance in

the Tables under the rise and the rafter thickness that you are

using (in our example: 8" rise and 1-1/2" actual rafter thickness,

resulting in a 7/8" allowance). Then make two plumb marks on

both sides of the rafter for the top plumb bevel cuts.
STEP 2. SEAT NOTCH: From the first top plumb mark,

measure down the rafter length (in our example: 20' 3-7/8")

and make the seat plumb mark (see Figure 13). Now, go

down the rafter from the seat plumb mark the miter al-

lowance distance (found in the table for your inch rise and

actual rafter thickness) and make a plumb line for the miter

allowance. Draw the same miter plumb line on the other

side of the rafter for making the bevel cut. This mitered seat

cut will allow the valley rafter to fit down over the crotch

formed by the joining wall plates (see Figure 12). Next, to

make the horizontal seat mark, measure down to the seat

depth on the seat plumb mark (not the miter plumb line).

Aligning the dashed line on our square with the seat plumb

mark, draw a perpendicular line using the bottom edge

of our Square to the edge of the rafter. Also extend the

horizontal seat mark to the added miter allowance plumb

line (see Figures 7 and 13). Double check to see that all seat

notches are the same depth.