Roof Drainage – Second Edition Now Available

Back To News
April 21, 2021
The new Roof Drainage – Second Edition is now available. This publication was funded by the RCI-IIBEC Foundation as an update of the 2003 edition of the Roof Drainage monograph as a result of significant changes in the International Building Code (IBC), the International Plumbing Code (IPC) and the methods used for roof drainage design. The authors of Roof Drainage are IIBEC member Stephen L. Patterson, RRC, PE, of Roof Technical Services, Inc. and Dr. Madan Mehta, PhD, PE, with the University of Texas at Arlington.

“We now know that the flow through a vertical leader and a roof drain are unrelated. Unlike the flow through a vertical leader, which is simply related to the pipe diameter, the flow through a roof drain is a function of several factors, such as the head of water over the drain’s rim, rim diameter, drain bowl depth, drain outlet diameter, and the strainer. As a result, the familiar plumbing code tables giving maximum drainable roof areas for roof drains became inapplicable and have been deleted from the codes. This left a large gap for the design disciplines to address.”


“Compounding the problem has been the continuing discrepancies between the three plumbing codes, which give different provisions for the same design issue. Existence of unexplainable discrepancies within the same plumbing code has been another problem. It is in this context that we decided to work on the second edition of Roof Drainage.”


“This monograph has been written as a textbook to serve all three disciplines—architecture, plumbing engineering, and structural engineering,” said Dr. Mehta. “We have learned a great deal since the 2003 publication and have incorporated it into this book.”


“Both Steve Patterson and Dr. Mehta deserve a great deal of thanks and praise,” said Mike Blanchette, chair of the RCI-IIBEC Foundation. “Their work on this publication took much longer than expected due to the complexity and changes that have taken place (in addition to the impact of COVID-19). The RCI-IIBEC Foundation is honored to have supported this work and we look forward to sharing this knowledge with the entire building enclosure industry.”


The publication is now available through the IIBEC website in both printed and electronic versions.