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

In the context of built-up roofing systems, it’s crucial for the exterior wall to extend a certain height above the roof to ensure proper drainage and to prevent water from infiltrating the building. A height of 30 inches above the roof is recommended in scenarios where there is a need for effective water management and potential compliance with relevant building codes and standards.

This height prevents water from accumulating on the roof and helps mitigate issues related to moisture and damage. Additionally, having the wall elevated adequately contributes to the overall durability and longevity of the roofing system by providing a barrier against wind-blown debris and other environmental factors.

Other heights mentioned, like 15 inches, 24 inches, or 36 inches, may either fall short of effective water management or be unnecessarily high, causing additional structural complexity or material costs. Thus, the 30 inches height strikes the right balance for functionality and cost-effectiveness in built-up roofing systems.