When you cut the rafters you ll need to make 3 separate cuts.
Roof rafter birdsmouth cut.
If you have never done.
You should now have a perfect birdsmouth cut in your first 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.
Because a roof requires many rafters to frame it speeds things along if you use the first rafter as a pattern or template for the other rafters.
With your ridge cut or plumb cut made you are now all set to.
This is the first stage of the process.
Please consult a professional before making any cuts i am not a professional framer or roofer nor do i claim to be.
Once you ve cut the top end of the first rafter you can calculate the position of the bird s mouth based on the height and width of the roof then use that rafter as a pattern to cut the others.
First off the plumb cuts are better left until all of the rafters are in place on the roof using a chalk line to get the plumb cuts in a dead straight line making the fascia board fit nicely.
A bird s mouth cut lets a rafter sit squarely down on the top of the wall rather than resting against it at an angle.
Here the birdsmouth plumb is 76 37 inches.
Making a birdsmouth joint.
It can be difficult to visualize rafter plumb and side cut angles and how the common hip and creeper rafters all fit together.
The actual indentation or cut is known as the birdsmouth while the birdsmouth plumb is the depth of the cut out.
For the rafter to fit correctly you need to cut the bird s mouth exactly where the rafter will meet the wall.
How to cut a birdsmouth joint calculating the pitch of a roof and making ridge cut.
To make it easier before you start to measure mark and cut print these templates fold over some scrap wood same size as rafters and cut through the paper to form the correct plumb and side cuts for common hip and creeper rafters.
Use it to make the proper measurements marks and cuts on each rafter.
Second even if the plumb cuts at the rafter s lower end have already been made small variations in rafter length and effects of bowed or arched rafters will throw off your birds mouth location.
Calculate rafter or joist length to birdsmouth location.
