1. What is Roof Rafter Length?

The roof rafter length is the diagonal distance from the outside of the wall plate to the center of the roof ridge. It's a crucial measurement in roof construction that determines the length of materials needed.

2. How Does the Calculator Work?

The calculator uses the rafter length formula:

Where:

• \( Run \) — Horizontal distance from wall to ridge (feet)
• \( Rise \) — Vertical height from wall to ridge (feet)
• \( \arctan \) — Inverse tangent function
• \( \cos \) — Cosine function

Explanation: The formula calculates the hypotenuse of the right triangle formed by the run and rise, which gives the rafter length.

3. Importance of Rafter Calculation

Details: Accurate rafter length calculation ensures proper roof construction, prevents material waste, and maintains structural integrity.

4. Using the Calculator

Tips: Enter run (horizontal distance) and rise (vertical distance) in feet. Both values must be positive numbers.

5. Frequently Asked Questions (FAQ)

Q1: What's the difference between run and span?
A: Run is half the span. Span is the total horizontal distance between outside edges of walls.

Q2: How do I measure run and rise?
A: Run is half the building width minus any overhang. Rise is the vertical height from top plate to ridge.

Q3: What's a typical roof pitch?
A: Common residential pitches range from 4:12 to 9:12 (4-9 inches of rise per 12 inches of run).

Q4: Does this account for overhangs?
A: No, this calculates the basic rafter length. Add overhang length separately if needed.

Q5: Can I use this for irregular roofs?
A: This is for simple gable roofs. Complex roofs require additional calculations.