How to cut a birdsmouth joint calculating the pitch of a roof and making ridge cut.
How to cut roof rafter birdsmouth.
Making a birdsmouth joint.
Set the framing square on top of the rafter beam with the tongue facing the top of the rafter.
Measure and mark plumb cut.
This is the first stage of the process.
Rise is the vertical distance from the top plate of.
Simple jig to cut your birds mouth notches.
Use the square root figure to measure along the top of the rafter.
Choose which end of your rafter you want to be the top.
The cut itself measures 90 degrees in order to rest snugly on the right angle of the 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.
Take a break from the measuring by cutting the top end of the rafter first.
Multiply your pitch by 24 to determine the rise per foot of run.
Pitch rise run x 2.
Draw a line at right angles to the bird s mouth plumb cut starting 3 inches up from the bottom of the rafter but no more than half the thickness of the rafter.
Make a mark along the top edge of the rafter where this measurement ends.
Calculate the pitch of your roof.
Calculate rafter or joist length to birdsmouth location.
If the roof has a 30 degree pitch the underside of the rafter and the vertical cut of the birdsmouth form a 120 degree angle.
This new line marks the horizontal cut for the bird s mouth.
Use a square placing one side against the plumb cut line.
The plumb or ridge cut is made at the top of the rafter.
The result of this equation represents the.
With your ridge cut or plumb cut made you are now all set to.
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.
This ensures that you make the birdsmouth cut at the right length in the rafter.
How to cut bird s mouths in rafters step 1.
