ROOF PONDING/DRAINAGE
ROOF PONDING/DRAINAGE
(OP)
In reviewing a roof plan with a relatively flat roof (typical office building structure) the roof slope is created by lowering the columns at interior bays. This results in about an 8" fall from the exterior wall.
However, there is only one drain shown at each location, and no overflow drain. Therefore, it seems this is very likely to have ponding problems, since the only overflow drain is a scupper on the exterior wall.
If a secondary drain was installed next to the primary drain, would this suffice to eliminate the ponding problems? The code says to assume the primary drain is blocked, however, I dont see any items regarding placement of the secodary drain. My thought was to install the secondary drain about 2" higher than the other, therefore, only needing me to check for 2" + localized pond, instead of an 8" pond + resulting beam deflections. Any thoughts?
However, there is only one drain shown at each location, and no overflow drain. Therefore, it seems this is very likely to have ponding problems, since the only overflow drain is a scupper on the exterior wall.
If a secondary drain was installed next to the primary drain, would this suffice to eliminate the ponding problems? The code says to assume the primary drain is blocked, however, I dont see any items regarding placement of the secodary drain. My thought was to install the secondary drain about 2" higher than the other, therefore, only needing me to check for 2" + localized pond, instead of an 8" pond + resulting beam deflections. Any thoughts?






RE: ROOF PONDING/DRAINAGE
The height of the water that can build up obviously needs to be less than the LL capacity of the roof.
RE: ROOF PONDING/DRAINAGE
It is not a good idea to use parapet overflows for centrally located internal drains. I've seen roof collapses related to such design. Provide an overflow for each drain location, separately piped to the outside. The depth of ponding prior to overflow should obviously exert less load than the live load capacity of the structure, as Jike noted.
RE: ROOF PONDING/DRAINAGE
RE: ROOF PONDING/DRAINAGE
RE: ROOF PONDING/DRAINAGE