1. What is Birdsmouth Heel Cut?

The birdsmouth heel cut is a notch cut into 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 that ensures structural stability and proper weight distribution.

2. How Does the Calculator Work?

The calculator uses the following formula:

Where:

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

Explanation: The cosine of the pitch angle determines what proportion of the rafter width needs to be removed to create a flat seating surface on the top plate.

3. Importance of Accurate Heel Cut

Details: Proper heel cut calculation ensures the rafter sits flush on the wall plate while maintaining the correct roof pitch. An incorrect cut can lead to structural instability or improper roof alignment.

4. Using the Calculator

Tips: Measure your rafter width precisely (typically 1.5" for 2x lumber). Enter the roof pitch in degrees (common pitches are between 20-45 degrees). The calculator will determine the exact depth of the heel cut needed.

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, hence the name.

Q2: How deep should the heel cut be?
A: Typically no more than 1/3 of the rafter depth to maintain structural integrity. Our calculator ensures this proportion is maintained.

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

Q4: What tools are needed to make this cut?
A: A circular saw or handsaw for the vertical cut and a chisel or reciprocating saw for the horizontal cut.

Q5: Should the heel cut be the same for all rafters?
A: Yes, all rafters for a given roof should have identical heel cuts to ensure uniform roof plane and weight distribution.