Westcon

Roof Drainage: What you don't know can hurt you

Presentation By: Phil Dregger, President
Technical Roof Services, Inc.

Understanding what needs to be done to comply with current codes as part of a new construction project is a relatively straightforward process (… note, I say “relatively”). This is not true for reroof projects and especially when it comes to compliance with the plumbing code. For example, if the existing roof has undersized overflow scupper drains, is it acceptable to leave them as they are or is a reroof project required to upgrade them to comply with the current plumbing code? Unfortunately, roof drainage provisions are often simply overlooked - sometimes with disastrous results. Topics to be addressed include:

Changes in building code and plumbing code requirements, including changes to allowable “tributary” roof drainage areas and to the required size of “secondary” scupper drains.
Confusion surrounding the meaning of phrases such as “maximum rainfall intensity” and “rainfall intensity in inches/hour lasting 5 minutes”.
Inadvertent reduction in roof drainage capacity associated with “insert” drains.
Case histories illustrating the results of “overlooked” roof drainage requirements and how local weather data and basic analytical procedures can be used to predict ponding conditions that preceded a major roof collapse during a very intense 15-minute rainstorm.

Philip D. Dregger is a long time Westcon member. He is a registered Professional Engineer (PE), Registered Roof Consultant (RRC), and President of Technical Roof Services, Inc. since 1991. Mr. Dregger received his Masters of Science Degree in Civil Engineering from the University of Minnesota with honors in 1978. Prior to coming to the West Coast in 1989, he investigated condensation, wind, wall and roof covering failures for Twin City Testing in St. Paul, Minnesota.

Mr. Dregger is a past Director of the Roof Consultants Institute and a former faculty member of the Roofing Industry Educational Institute. He serves on the executive committee of the special ad hoc Roofing Industry Committee on Wind Issues.