How To Birdsmouth A Roof Rafter

How to cut bird s mouths in rafters step 1.

How to birdsmouth a roof rafter.

Possibly the most satisfiying part of the roof yet. This notch allows the beam to rest flush onto the top plate. So to summarise the full process is as follows. 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.

Due to the width. Multiply your pitch by 24 to determine the rise per foot of run. Calculate pitch of roof use roof pitch to cut ridge cut use ridge cut as point of reference to form birdsmouth make tail cut. How do i know where to cut the bird s mouth in a rafter.

The roof rafters provide integral structural support to the roof. Before you cut your boards you ll need to measure the width of your building and calculate the exact length of each 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. When it comes to laying out a rafter it s essential to understand the basic building blocks of framing.

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. This 90 degree angle forms the bird s mouth. Rise is the vertical distance from the top plate of. Pitch rise run x 2.

From that line across the rafter draw a perpendicular line at the 1 1 2 inch mark out towards inside part of the rafter. When you cut the rafters you ll need to make 3 separate cuts. Also known as a bird s mouth joint or sometimes a bird s beak notch this type of cut is typically used to securely connect a rafter to the top of a supporting wall with the help of a wall plate. 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.

A birdsmouth cut involves taking a notch shaped like a bird s mouth out of each rafter where it meets the top plate. The result of this equation represents the. 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. Among the most important individual components is the birdsmouth joint.