The Uniform Building Code (UBC), 1988 Edition,
requires roof systems to be sloped a minimum of 1/4 inch
in 12 inches for positive drainage.
Most manufacturer warranties require roofs
to be free of ponding water 48 hours after a rainfall
(consult individual manufacturer's specific requirements).
Where water cannot drain over the roof edge,
the UBC requires a roof drain and an overflow drain at
every low point of the roof.
Scuppers, or openings through the wall,
can be used in lieu of overflow drains. the UBC requires
that overflow scuppers be three times the size of the
roof drain and have an inlet line located a maximum of
2 inches above the adjacent low roof point.
