Commercial Drainage Scupper & IBC Code Sizing Tool

The International Building Code (IBC) requires secondary (overflow) scuppers to be sized at least as large as the primary drains and located 2 inches higher. Failing to meet this standard on a commercial reroof is a major structural liability if a primary drain ever clogs.

Always use a high-quality flashing membrane and ensure the scupper is 'set in a bed of mastic.' Professional custom-bent metal scuppers with wide flanges provide the best 'tie-in' to your main roof field, significantly reducing the risk of a high-consequence failure at the parapet wall.

Charge $250–$450 per scupper. This includes the custom metalwork and the high-skilled labor required to tie the scupper into the existing TPO or EPDM system. Don't include this in your general square count; it's a specialty technical detail that warrants a separate line item.