When you cut the rafters you ll need to make 3 separate cuts.
Roof rafter birdsmouth cut.
Please consult a professional before making any cuts i am not a professional framer or roofer nor do i claim to be.
This trick worked for me.
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.
Use it to make the proper measurements marks and cuts on each 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.
For the rafter to fit correctly you need to cut the bird s mouth exactly where the rafter will meet the wall.
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.
This is the first stage of the process.
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.
It can be difficult to visualize rafter plumb and side cut angles and how the common hip and creeper rafters all fit together.
You should now have a perfect birdsmouth cut in your first rafter.
Creating a birdsmouth cut is the classic way to prepare a rafter for a hand cut gable or shed roof.
Calculate rafter or joist length to birdsmouth location.
If you have never done.
Birdsmouth plumb if you study the diagram carefully you will see that there is an indentation in the roof rafter where it meets the exterior wall of the building.
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.
The actual indentation or cut is known as the birdsmouth while the birdsmouth plumb is the depth of the cut out.
Making a birdsmouth joint.
With your ridge cut or plumb cut made you are now all set to.
How to cut a birdsmouth joint calculating the pitch of a roof and making ridge cut.