Roof Rafter Layout

Rafter run outer wall this should be measured starting from the center of the roof span and then extending to the very edge of the exterior wall.

Roof rafter layout.

For a gable roof the run is measured from the centerline of the ridge board to the outside edge of the top of the wall. Draw a line down the edge of the tongue as shown in illustration b of the roof layout. Run is the horizontal distance that the rafter covers. The table states that 2 x 6 rafters spaced 16 inches on center o c can span a maximum distance of 13 feet 5 inches.

Measure up a distance equal to 25 of the width of the rafter as shown in illustration c and put a mark. Another option are 2 x 8 rafters spaced 24 inches o c. In the gable roof example shown here a rafter with 6 in 12 pitch rises 6 in. Here the number is 1166 66 inches.

For every foot of run. Let s use this example and find a size of rafter that will work. Once you know the pitch and the total run you can lay out the cuts of the rafter in a number of ways. To lay out a common rafter you need the pitch of the roof expressed in units of rise per foot of run.

Flip the square over and place the tongue along the line made in illustration b. Here the number is 941 86 inches. Roof rise this should be calculated from the base of the roof to the highest point of the roof gable the peak. Marking the birdsmouth and the ridge board setback.

Looking through the center of the table we can find a couple of options.