Several black zinc panels on U.S. Bank Stadium came loose during Tuesday night's storm, and stadium officials were at a loss to explain why Wednesday.
Mortenson Construction vice president John Wood said the "extreme weather" caused the panels to partially disengage along their top edges, although none fell off. "The panels will not need to be replaced, just reinstalled, unless the panels themselves were damaged," Wood said.
Minneapolis-based Mortenson, the general contractor on the building, is working with the architects, Dallas-based HKS; the sheet metal subcontractor, Maplewood-based MG McGrath Inc., and other experts to understand why the panels are coming loose and how to fix them, Wood said.
Unsecured rectangular panels are more than a tangential concern because U.S. Bank Stadium's exterior walls are lined with thousands of them.
Minnesota Sports Facilities Authority (MSFA) Chair Michele Kelm-Helgen said it wasn't the first time the panels have come loose.
In a previous incident several weeks ago, the panels were believed to be loose because of other work to fix a moisture problem, but now the two appear unrelated, she said.
Since February, Mortenson has worked to address dampness on a parapet wall and some pooling of water in a gutter. The water had yet to seep into the building's interior walls, but the company was installing a new moisture barrier at an estimated cost of $4 million.
Replacing the old barrier required removing some of the black panels encircling the building's exterior.
