Roof Drains for patios of multistory buildings

[bkengr18206]

I am designing a 11 story condo building that has stepped back roof terraces on the upper 6 levels. The code requires a roof drain with an overflow above the drain. How have others handled this overflow drain. The architect has the roof drain(s) in the center of the terrace and doesn't want any protrusion above the terrace. Any suggestions would be appreciated.

Second question In this city we have experienced water backing up and filling the roof leaders of multistory buildings due to the inadequacy of the city drainage system during high intensity storms. Does any one know of a device to relieve this condition when it occurs.

 

[PEDARRIN2]

Secondary drainage is required in case the primary drain blocks. It can be met by overflow drains, scuppers in a parapet or the roof structure will have to be designed to support any ponding water. The first two are the most typical I have seen.

See if there will be a parapet on the terrace. If that is the case, the architect can put scuppers 2-4" above the terrace level. This should satisfy the secondary drainage requirement.