R903.4.1

Section R903.4.1 is titled 'Secondary (emergency overflow) drains or scuppers' and covers requirements for roof coverings. The requirement for a secondary emergency drain or scupper where water can become entrapped on the roof if the primary drain is blocked, the size and inlet flow line height above the low part of the roof, and a cross-reference to another code which covers details on installation and sizing is established. The purpose of this section is to prevent structural and water damage to the building.

The model shows a flat roof assembly with a primary drain in the center and secondary emergency scupper cut into the raised roof edge.