Where a roof and a parapet wall meet, how far above the roof line must the parapet wall extend?

The correct extension height of the parapet wall above the roof line is typically determined by building codes and safety standards, which often require a minimum height to prevent falls and allow for adequate water drainage. The standard height of 30 inches is commonly referenced in various building codes for areas where a roof and parapet wall meet. This height is considered sufficient to ensure safety for individuals who may be working or walking near the edge of the roof while also providing structural integrity and aesthetic continuity to the building design.

Maintaining this height requirement also helps prevent wind uplift issues and adequately shields the roof edges from debris and other external elements. Lower heights might not offer adequate safety or may not comply with local regulations, which is why the specified height of 30 inches serves an essential purpose in roof construction and design.