On a built-up roof, how much higher should the exterior wall be than the roof where the roof and exterior walls meet?

• A. 12 inches
• B. 24 inches
• C. 30 inches
• D. 36 inches

Answer: (C)

The correct choice indicates that the exterior wall should be 30 inches higher than the roof where it meets the exterior walls on a built-up roof. This height is important for several reasons related to building design and structural integrity.

First, this height helps manage water drainage and prevents water from pooling at the edge of the roof, which can lead to leaks and structural damage over time. A taller parapet wall helps ensure that rainwater flows away from the building's exterior, minimizing the risk of moisture-related issues.

Second, having the exterior wall at a sufficient height creates a more effective barrier against wind-driven rain and minimizes the chances of wind uplift, which can damage both the roofing and the building envelope.

Moreover, from a safety and aesthetic standpoint, a taller parapet wall can also provide a more secure environment by preventing individuals from easily accessing the roof area, thus enhancing the overall safety of the structure.

In summary, positioning the exterior wall 30 inches higher provides functional benefits in terms of water drainage, structural protection, and safety, making it a commonly accepted standard in building practices for built-up roofs.