Crowd Consulting Conundrum

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August 24, 2017

EDITOR’S NOTE: This occasional feature is presented as an opportunity for building envelope consultants to present and weigh in on puzzling situations encountered in the course of one’s work. If you have a similar experience that might benefit from a little “crowd consulting” advice, or a theory about one of the previously published subjects of a Crowd Consulting Conundrum, please send it, with accompanying high-resolution photos, to Editor Kristen Ammerman at kammerman@iibec.org.

I have an unusual problem with a KEE or KEE-containing roof membrane and want to ask my roof consulting brothers and sisters for help with solving it. The membrane exhibits concentric fractures over plates—mostly over metal inseam plates, but also over some metal and even plastic insulation plates. The roof assembly, from top to bottom, consists of the thermoplastic membrane, a cover board, polyisocyanurate insulation, and a steel deck. See accompanying photos.

Initially, I thought the fractures were related to hail impacts, and the membrane does appear susceptible to fracturing by rather modestly sized hail. However, careful observation indicated the “plate” fractures are separate and distinct from hail impact fractures. Also, the “plate” fracture conditions were found on roofs with no reported prior hail events.

I have observed the “plate” fractures on sites across the U.S.—from Florida to California and from Minnesota to Texas. The installations range in age from seven to nine years. Many of the fractures extend down to the reinforcing fabric; but to date, I have seen no fractures extend completely through the bottom film of the sheets. The back sides of the sheets are also discolored/faded in a way I’ve not seen before.

If you have seen similar “plate” fractures, or if you have a working theory as to why the fractures occur where they do, please send us an email with example photos. If we find out anything conclusive, we will follow up.

Phil Dregger
Technical Roof Services
Concord, CA