Roof Drainage Not my problem... Maybe

Many strucrural engineers are surprised to learn that the In~rnotional Building Code (IBC, 2009) requires the roof structure to be engineered for standing water weight in the vicinity of the drains and scuppers regardless of roof slope. In addition, some low-slope roofs also require special attenlion for water weight and stiffness for safety against ponding failures or protection against accelerated roofing deterioration. With a mixture of overlapping design disciplines between the archi~t, plumbing consultant and structural engineer, proper roof drainage is often not fully addressed in building design and can lead to catastrophic collapse. The author has been involved as an expert consultant in several roof collapses in California due to excessive rain water accumulation, and brings some lessons learned to the profession. This paper provides an overview of the various disciplines involved in transporting rainwater from roofs, and recommendations for engineers to comply with code requirements