Where the roof and exterior walls come together, how much higher should the exterior wall be than the roof on a built up roof ?

Where the roof and exterior walls come together, how much higher should the exterior wall be than the roof on a built up roof ?

• A. 40 inches
• B. 10 inches
• C. 30 inches
• D. 20 inches

Answer: (C)

Parapet height around a built-up roof is the idea being tested. On a built-up roof, the exterior wall should extend thirty inches above the roof surface to form a protective parapet. This height provides a proper edge condition for flashing and weatherproofing, helps resist wind-driven rain at the roof line, and gives a safe, practical edge for maintenance and coping installation. If the wall were much lower, there wouldn’t be enough protection or a suitable surface for flashing details; being much higher adds unnecessary cost without added functional benefit. Thirty inches is the standard practice for achieving these edge conditions.

Parapet height around a built-up roof is the idea being tested. On a built-up roof, the exterior wall should extend thirty inches above the roof surface to form a protective parapet. This height provides a proper edge condition for flashing and weatherproofing, helps resist wind-driven rain at the roof line, and gives a safe, practical edge for maintenance and coping installation. If the wall were much lower, there wouldn’t be enough protection or a suitable surface for flashing details; being much higher adds unnecessary cost without added functional benefit. Thirty inches is the standard practice for achieving these edge conditions.