b'BUILDING CODEFigure 2: If the small central drain is overwhelmed, the doorway will act as the overflow.Figure 3: A hospital build with a parapet approximately two feet (500 mm) high with no overflows. This door would act as an overflow if the roof drains become overwhelmed or blocked.At this building, which is a hospital, there is a parapet that is approximately two feet (600 mm) 28 lROOFINGBClFALL 2024high with no overows. The structure may be designed to accommodate the weight of water, but the door into the hospital would act as an overow if the drains were overwhelmed or blocked.In general, code compliance on exisng buildings is grandfathered, meaning that compliance with the code of the date of the permit is adequate. While grandfathering can work for elements such as insulaon, cladding or air changes per hour, ignoring updated code or climate data on roof drainage of exisng buildings can result in life and safety issues. Another consideraon on new construcon is whether todays climate data should be relied on for something that is a life and safety issue. While codes are being updated to consider forward-looking climate data, the current code does not require that to be considered. In my opinion, a designer should be allowing for increased intensity weather events, either through rethinking drainage strategies (eliminang parapets, increasing load capacies of roofs) or increasing drainage capacity in excess of current code requirements. Remembercode is a minimum standard. Some approaches (removing parapets) can result in other implicaons where a municipality has rain water retenon direcves, including ow control drains and other measures.'