Roof Rafter Layout

For every foot of run.

Roof rafter layout.

Looking through the center of the table we can find a couple of options. For instance 2 grade 2x4s at 16 on center will span just over 9. Draw a line down the edge of the tongue as shown in illustration b of the roof layout. To lay out a common rafter you need the pitch of the roof expressed in units of rise per foot of run.

There is no standard spacing it depends on what size of rafters you want to use and the span of your shed. Roof rise this should be calculated from the base of the roof to the highest point of the roof gable the peak. Flip the square over and place the tongue along the line made in illustration b. Let s use this example and find a size of rafter that will work.

Run is the horizontal distance that the rafter covers. Marking the birdsmouth and the ridge board setback. Here the number is 1166 66 inches. 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.

In the gable roof example shown here a rafter with 6 in 12 pitch rises 6 in. Another option are 2 x 8 rafters spaced 24 inches o c. 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. For standard shed roof rafter spacing see rafter span chart.

Once you know the pitch and the total run you can lay out the cuts of the rafter in a number of ways.