1. What is the Common Rafter Length Formula?

The Common Rafter Length Formula calculates the length of roof rafters using the Pythagorean theorem. It's essential for proper roof framing and construction planning.

2. How Does the Calculator Work?

The calculator uses the formula:

Where:

• \( Run \) — Horizontal distance from outside of wall to center of ridge (feet)
• \( Rise \) — Vertical height from top of wall to peak of roof (feet)

Explanation: This formula applies the Pythagorean theorem to calculate the hypotenuse of a right triangle formed by the run and rise measurements.

3. Importance of Rafter Length Calculation

Details: Accurate rafter length calculation is crucial for proper roof construction, material estimation, and ensuring structural integrity of the building.

4. Using the Calculator

Tips: Enter run and rise measurements in feet. Both values must be positive numbers. The calculator will determine the rafter length needed for your roof framing project.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between run and span?
A: Run is half the span. The span is the total width of the building, while run is the horizontal distance from the outside wall to the center of the ridge.

Q2: Should I add extra length for overhangs?
A: Yes, this calculation gives the basic rafter length. You'll need to add additional length for any desired roof overhang beyond the wall.

Q3: How accurate should my measurements be?
A: For construction purposes, measurements should be precise to at least 1/8 inch to ensure proper fitting of rafters.

Q4: Does this work for all roof types?
A: This formula works for common rafters in simple gable roofs. Hip roofs, valley rafters, and jack rafters require different calculations.

Q5: What about roof pitch?
A: The rise and run measurements inherently account for roof pitch. The steeper the roof, the greater the rise relative to the run.