How To Layout A Roof Rafter

Marking the birdsmouth and the ridge board setback.

How to layout a roof rafter.

Let s consider a basic gable wood roof framing design. Use a tape measure to measure the entire width of your building. Then draw a line across the width of the plywood from that mark. Just share the link.

Rafter layout with a framing square this example is for a roof with an 8 12 pitch position the square at the end of the rafter board with the tongue on your left and facing away from you. Align the back edge of the tongue with the 187 7 8 mark. The easy way to lay out and build your rafters. Measure as precisely as possible down to the 1 4 inch 0 64 cm 1 8 inch 0 32 cm or 1 16 inch 0 16 cm.

Here we have a wood framed gable roof. In the gable roof example shown here a rafter with 6 in 12 pitch rises 6 in. To lay out a common rafter you need the pitch of the roof expressed in units of rise per foot of run. The image below shows a cross section of our simple 12 x 13 house from the joist span tables section of this tutorial.

We need to adjust the total run 73 inches in our example by subtracting 1 1 2 inches the full thickness of the ledger adjusted run 71 1 2 inches. Place the square as before aligning the 6 mark of the tongue and 12 mark of the body with the top edge of the rafter material. Before you start cutting you first need to determine how long your roof rafters need to be and the angles at which you ll cut the top and bottom of the rafter. Run is the horizontal distance that the rafter covers.

Position the square with both the 8 inch on the outside edge of the tongue and the 12 inch on the blade on the upper edge of the board. On a shed roof rafter run is the distance from a ledger on the main building to the outside of an addition wall or porch carrying beam. Facing the long side of your material measure down from the top edge 8. Floor beam span tables of residential structural design we will now look at roof rafter and beam design.

Draw a line down the edge of the tongue as shown in illustration b of the roof layout. Use a circular saw or jigsaw to make the cut. Rafter layout and cutting sequence. Layout your sheet of plywood on sawhorses.