Common Rafter Calculator

What is a Common Rafter Calculator?

A “Common Rafter Calculator” is a tool used to determine the dimensions of common rafters used in roofing.

It calculates the length of the common rafter, along with other dimensions like the plumb cut and tail overhang, based on the roof span and pitch.

Why use a Common Rafter Calculator?

Using this calculator is important for several reasons:

• Roof construction: It helps carpenters and roofers in planning and cutting common rafters to the correct size.
• Safety: Accurate rafter dimensions are crucial for ensuring a secure and stable roof structure.
• Aesthetics: Properly cut rafters contribute to the overall appearance of the roof.

How to use a Common Rafter Calculator:

1. Input the roof span (in feet), which is the horizontal distance from the wall to the peak of the roof.
2. Input the roof pitch (e.g., 6/12, 8/12), which represents the slope of the roof as a ratio of rise to run.
3. Click the "Calculate" button.
4. The calculator estimates the common rafter length, plumb cut, and tail overhang.

Example calculation:

If you input a roof span of 20 feet and a roof pitch of 6/12, the calculator will estimate that the common rafter length is approximately 22.80 feet, the plumb cut is approximately 5 feet, and the tail overhang is approximately 10 feet.

These dimensions can vary depending on specific roof design and construction techniques.

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