What does mean roof height refer to?

• A. The maximum height of the roof above grade.
• B. The average height of the roof surface above grade.
• C. The height of the tallest roof element.
• D. The height of the eave line.

Answer: (B)

Mean roof height is the average height of the roof surface above grade. When a roof has varying elevations due to slopes, multiple sections, or parapets, designers use this single representative value to reflect how high the roof sits overall, which matters for calculations and specifications that depend on height above ground. Taking the mean avoids overestimating by picking only the highest point or underestimating by using just the lowest point, like the eave line. For example, if different parts of the roof sit at several heights, the mean height smooths those variations into a practical figure for wind design, drainage considerations, and related requirements.