Birdsmouth
A Birdsmouth consist of two cuts, the horizontal seat cut and the vertical heel cut.
This calculator calculates the location of the plumb line for the heel cut on your rafter (lenght A to B), and the lenght of the matching seat cut.
Note
According to the International Residential Code, the depth of the heel cut can be no more than one-quarter the width of the material you are using for rafters. If you are using a 2 x 12 for a rafter, then the maximum allowable depth of the heel cut will be 2 13/16 inches. A 2 x 4 rafter's heel cut can be no more than 7/8 of an inch deep.
Birdsmouth Location and Cuts
Calculation
- building width in feet and inches (outside sheating to outside sheating)
- ridge board thickness in inches
- wall + sheating thickness in inches
- slope ratio, amount of rise per foot of run in inches
- depth of heel cut
Results
- length from A to B (measured from the top of the ridge cut to where you have to draw the plumb line for the heel cut on your rafter)
- A to B length in inches
- seat cut depth ( when the seat cut length exceeds the width of the wall WARNING!!)
Advanced Construction Calculator
Roof Framing
- Birdsmouth Cut, The Heel
- Birdsmouth: Heel Cut, Seat Cut
- Birdsmouth Seat Cut
- Convert a Roof Pitch to an Angle
- Heel Cut of a Birdsmouth
- Heel Cut Length (Metric)
- Height Above Plate (HAP) with Heel Cut Depth
- Height Calculation for a Common Truss
- Rafter Length
- Rafter Length (Metric)
- Rafter Length Calculated in Metres (with rise, run, post height, birdsmouth)
- Rafter Lengths, Hip and Common
- Rafter Length (with rise, run, post height, birdsmouth)
- Roof Measurement
- Roof Pitch
- Roof Sheathing - Gable (Imperial)
- Roof Sheathing - Gable (Metric)
- Roof Sheathing - Hip Roof (Imperial)
- Roof Sheathing - Mansard (Imperial)
- Roof Sheathing - Shed (Imperial)
- Slope, Roof, Hip Valley, Height and Width Factors