Roof Framing

Overview

Engineering reference data for Roof Framing in building construction.

Key Formulas

U-value

$U = \frac{1}{R_{total}}$

Overall heat transfer coefficient.

Heat Loss

$Q = U A \Delta T$

Heat transfer through building envelope.

Variables

Additional Formulas and Concepts

Run Calculation

The run is half the total span of the roof. $R = \frac{S}{2}$ where:

• $R$ = run (ft, m)
• $S$ = span (ft, m)

Gable Height

The vertical height of the gable end is calculated from the run and the roof's vertical rise. $GH = R \cdot VR$ where:

• $GH$ = gable height (ft, m)
• $R$ = run (ft, m)
• $VR$ = vertical rise (in/ft, cm/m)

Gable Area

The area of the triangular gable end is: $GA = \frac{GH \cdot R}{2}$ where:

• $GA$ = gable area (sq.ft, m²)
• $GH$ = gable height (ft, m)
• $R$ = run (ft, m)

Roof Slope (Pitch)

Slope is the tangent of the roof angle, representing the ratio of vertical rise to horizontal run. $RS = \frac{y}{x}$ where:

• $RS$ = roof slope
• $y$ = vertical rise (in, cm)
• $x$ = horizontal run (in, cm)

Common Conventions:

• U.S. Customary: Expressed as inches of rise per 12 inches of run (e.g., 4:12 pitch).
• Metric: Often expressed as a percentage (e.g., 21.8% for a 4:12 slope) or as a ratio over 10 or 100 (e.g., 4:10).

References

• Original Source