The Unforeseen Impact of Building Modifications to a Roofing Assembly

The case study involves an industrial building that was constructed in the early 2000s with a low-sloped, mechanically fastened, single-ply membrane roofing system, with parapet walls that transitioned to mansard roofs with standing-seam metal panels. An expansion was performed adjacent to the building in 2014 that added a pitched roof along the interface that penetrated an existing parapet wall and mansard roof assembly. Additionally, changes to the operation of the building were made that required a regulated internal humidity level of 45% (relative humidity) with a frequent air exchange rate. Within 4 years post construction, the roofing membrane was noted to be billowing and sections of the membrane had become unbonded from the parapet wall. Further investigation revealed that the mechanical roof connectors were severely corroded and failing throughout with significant moisture present indicating a large-scale issue. Analysis of the building was performed which identified significant hygrothermal issues. The findings of this investigation initiated a complex design and repair to the existing building.