How To Birdsmouth A Roof Rafter

The ridge cut also called the plumb cut at the top of the rafter the birdsmouth cut which itself comprises 2 different cuts where the rafter meets the building s wall and the tail cut at the base of the rafter.

How to birdsmouth a roof rafter.

Calculate the pitch of your roof. Measure along the top of the rafter the distance that you calculated in the previous step. This notch allows the beam to rest flush onto the top plate. Before you cut your boards you ll need to measure the width of your building and calculate the exact length of each rafter.

Among the most important individual components is the birdsmouth joint. Pitch rise run x 2. From the marked point draw a line at the same angle as the pitch of the rafter up and make a mark at 1 1 2 inches. In my photo above the green rafter line length is from the plumb cut face or ridge board face to the plumb cut face of the bird s mouth notch.

Multiply your pitch by 24 to determine the rise per foot of run. From that line across the rafter draw a perpendicular line at the 1 1 2 inch mark out towards inside part of the rafter. The result of this equation represents the. Make one rafter that has the bird s mouth cut in place and extends out past that for your roof overhang test fit it in place and mark it pat for pattern rafter to use in cutting its sisters.

Calculate pitch of roof use roof pitch to cut ridge cut use ridge cut as point of reference to form birdsmouth make tail cut. So to summarise the full process is as follows. How do i know where to cut the bird s mouth in a rafter. Measure or calculate the height of the roof from the top of the wall to the top of the ridge plate and multiply that number by itself.

Possibly the most satisfiying part of the roof yet. Due to the width. A birdsmouth cut involves taking a notch shaped like a bird s mouth out of each rafter where it meets the top plate. The roof rafters provide integral structural support to the roof.

Step 3 cutting out the bird s mouth. How to cut bird s mouths in rafters step 1. Rise is the vertical distance from the top plate of. When you cut the rafters you ll need to make 3 separate cuts.