What should be the Roof slope to prevent Ponding?

As per standards, the Roof beams should have a continuous upward slope equivalent to 1/4 in/ft ( 20.8 mm/m) between a drain and the high point of a roof, in addition to minimum recommended camber to avoid ponding.

In case of insufficient slope that is less than 20.8mm/m, it should be noted that the stiffness of supporting members acting 5lb/ft2 or 239.4 N/mm2 load should not cause more than 1/2 inch or 12.7mm deflection.