Roof Collapse Case Study: Drainage Design Issues

A section of the roof for a warehouse structure collapsed after a rainstorm event during the summer of 2006. Given the location of the building, one may be surprised to find that such a roof would collapse after a rain event rather than a snow event. Was it an unusually heavy rain event? Were there errors in the structural design of the building? Were there problems with the fabrication/installation of the roof joists, girders and columns? Were there errors in the design and installation of the roof drains and associated plumbing? Surprising, none of these issues proved to be the culprit. This paper steps through our forensic evaluation of this case, and briefly reviews roof drainage design considerations. From the collection of weather data, through our consideration of various failure hypotheses, we will show the forensic methodology that led us to a very interesting conclusion.