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Beetles Can Bore Holes In Your Building Envelope

July 8, 2019

Over thirty years ago, our company installed the roof on a new museum in Montgomery, Alabama. The building is a magnificent structure, including a roof-top dome clad with shop-formed, terne-coated standing-seam stainless-steel, surrounded by a ballasted EPDM roof over lightweight insulating concrete.

Construction of the museum began in early 1986, and the roof system was completed later that year. In June of 1987, the museum’s upcoming grand opening was only ten days away. Scores of near-priceless artworks were being placed throughout the museum and, beneath the signature dome, some of the most valuable paintings that would be on display during the event had already been professionally installed. 

As is common during the summer in the South, a large thunderstorm popped up. The storm produced the first substantial rainfall since April of that year. During mid-afternoon as the storms moved across the city, we received a frantic call from the project’s general contractor. We were told the area around the dome was leaking badly. Despite the ongoing downpour (complete with thunder and lightning), the general contractor demanded that our firm produce a crew on site immediately to stop the leaks. For emphasis, the general contractor reminded us of the presence of those valuable paintings now installed below the dome.

Our repair crew rushed to the site to determine the source of the leaks and help mitigate any additional damage. As our 25-year veteran repair foreman reached the exterior base of the dome, where the horizontal EPDM roof membrane terminated and the vertical EPDM flashing material tied in to seal the wall detail, he found dozens of holes in the flashing material. Without hesitation he applied mastic over the damaged flashing and stopped the water intrusion. 

As we discussed the source of the leaks later that afternoon, our only conclusion was possible vandalism by a disgruntled tradesman from another crew working in the roof area after our work had been completed. However, the following day, with sunny weather and a full crew at the museum, our “post-mortem” inspection revealed a situation that no one had suspected. As the crew began removing the damaged flashing from the base of the dome, hundreds of beetles were found. Apparently, they had burrowed into the uncured EPDM material to mate and died under the flashing. Of course, we were dumbfounded by the discovery. However, now the more urgent matter was what to do to replace the damaged flashing. Clearly, if we used the same type of EPDM material to make the repairs, beetles and accompanying leaks would almost certainly return.

Obviously, the mid-1980’s was BG (Before Google). So, we placed a call to the roofing manufacturer’s technical support department, but they, too, had never experienced this situation before. So, we were on our own to resolve the problem. 

At that time, the typical protocol to seal the horizontal-to-vertical detail—where a flat roof intersects with a wall—was to install an “uncured” EPDM membrane. The uncured version of EPDM is softer and more pliable than the “cured” EPDM product which was used for the main roof system on the rest of the building. During our investigation, we also discovered that no beetles had penetrated the flat roof, which consisted of the cured EPDM roof membrane. So, while it was a good bit more labor intensive, we replaced all of the uncured EPDM around the dome base with the cured variety of EPDM. However, as we continued with our inspection of all the other areas where uncured EPDM had been specified for this roof system, we found virtually no other damaged uncured EPDM and very few dead beetles on the roof. 

As we continued to evaluate the conditions that were different related to the roof section around the dome compared with the rest of the roof system covering some 44,000 sq. ft., a member of our team pointed out that the museum dome was highlighted at night by powerful spotlights with the balance of the roof being dark after sunset. The following day, one of our team members contacted the state entomology lab. After describing our dilemma at the museum to one of the entomologists, we were told the culprit was the Japanese Beetle. We were advised that they tended to mate in the earlier part of the summer and, as the beetles emerged from burrows in the grassy meadows surrounding the museum at night, they were likely attracted to the dome lighting and followed it to its source to commence their mating cycle.

Even though we had identified the culprit, we were faced with the problem of the lights continuing to attract the beetles at night. And, while we were relatively sure the cured EPDM was resistant to the beetles, there was expensive inventory below the roof so we felt compelled to solve the lighting issue. Knowing the lights highlighted the museum’s primary exterior attraction – the dome – removing the lights was not an option. However, after extensive research, we learned that we could change the type of ballast in the lights to ones which would not attract the beetles. So, in the end, that was our final solution to putting an end to “beetle-mania” on the roof of The Montgomery Museum of Fine Arts.

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