1. What is Birdsmouth Seat Cut?

The birdsmouth seat cut is a notch in a rafter that allows it to sit flat on the top plate of a wall while maintaining the proper roof pitch. It's an essential part of roof framing.

2. How Does the Calculator Work?

The calculator uses the seat cut formula:

Where:

• \( \text{rafter\_width} \) — Width of the rafter (inches)
• \( \text{pitch} \) — Roof pitch angle (degrees)

Explanation: The sine function calculates the vertical component of the rafter width based on the roof pitch angle.

3. Importance of Seat Cut Calculation

Details: Accurate seat cut calculation ensures proper roof framing, structural integrity, and correct load transfer from the roof to the walls.

4. Using the Calculator

Tips: Enter rafter width in inches and roof pitch in degrees. The pitch should be between 0 and 90 degrees.

5. Frequently Asked Questions (FAQ)

Q1: Why is it called a birdsmouth cut?
A: The notch resembles the shape of a bird's mouth when viewed from the side.

Q2: How deep should the seat cut be?
A: Typically no more than one-third the depth of the rafter to maintain structural integrity.

Q3: Does this work for all roof pitches?
A: Yes, the formula works for any pitch from 0 to 90 degrees.

Q4: What about the heel cut?
A: The heel cut is typically perpendicular to the seat cut and completes the birdsmouth notch.

Q5: Can I use this for uneven rafters?
A: This calculator assumes standard rectangular rafters. Special calculations are needed for irregular shapes.