Mechanical Curb Height in relation to Secondary Scuppers


Is anyone aware of any code standard for the minimum height of mechanical curbs in relation to the elevation of secondary drainage? I have a case where they installed relief scuppers in the parapets at an elevation about 6" above all of the mechanical curbs, vents, and access hatch. Seems like a water damage disaster waiting to happen if the main drain clogs.


In the past month, Ive been on two projects for repairs. A modified church and a strip center with TPO. Both properties, we had to blow off the areas for repair, because of tree debris. Both of these properties had the scuppers, even with the deck. The drains were about 6ft from the parapet. I can’t remember any scuppers being above the deck, so I went to the IBC.
97 UBC (CBC 2001)1506.3 Overflow Drains and Scuppers. Where roof drains are required, overflow drains having the same size as the roof drains shall be installed with the inlet flow line located 2 inches above the low point of the roof, or overflow scuppers having three times the size of the roof drains and having a minimum opening height of 4 inches may be installed in the adjacent parapet walls with the inlet flow line located 2 inches above the low point of the adjacent roof.


Yea, i saw that requirement too in old codes which no longer legally apply. Have you seen anything from modern standards? More modern codes took out that 2" clause and only say that the roof structure has to be capable of supporting the weight, and it makes no mention of the situation where clogging of the main drains create a situation where water pours into every mechanical unit and vent.


Sounds like a common sence issue long before becoming a code issue.


Yea, I think it’s more of a standard of practice thing unless someone here knew of an odd code provision. Is why I asked. Sometimes these provisions are buried within the MEP codes. Or maybe does curb manufacturer.

Anyone know if this issue shows up in the NRCA’s recommendations?