b'ARCHITECTURAL SHEET METALFigure 3A symmetrical standing-seam roofing panel.double-folded, structural standing-seam panel, Brown explains. The two main leak sources in the original roofexposed fasteners penetrating the roof deck and end lapsare easily over-come by using Figure 2A standard double-lock, standing-seam metal roofinga free-floating standing-seam system with panels panel. that run full length from top to bottom. This system laps and where fasteners are installed. Thermalwill have no horizontal lap joints and no exposed movement helps to elongate the holes where thefasteners to leak. The 180-degree double-folded screws penetrate the panels. Louisiana also receivesstanding seams provide the best wind uplift and some of the most intense sun and torrential rains inwatertight-ness available.North America, both of which accelerate aging of allRe-cover is the best option for our tenants because roofing materials. it provides the least disruption to their operation and Structurally, the buildings remain in good shape,offers an opportunity for us to add insulation between says Brown, and by employing several differentthe new and old roof.metal retrofit systems, weve been able to avoid theThere are other significant advantages to re-covering. expense of tearing down a building and rebuilding aWhile all structures should be inspected by a qualified replacement. Weve re-covered more than a dozendesign professional prior to doing any work of this hangars and assorted outbuildings over the past 12nature, re-covering over an R-panel does not alter years.the structural diaphragm, since the exposed fastener EVOLUTION OF THE RE-COVERpanel that remains in place is an integral part of Our job here is to provide long-term value to ourthe structure. Also, the system weighs less than 3 client, and our client does not want short-term fixes,pounds per foot, so it falls within the guidelines of Brown says. Many of these exposed fastener systemsthe International Building Code (IBC) for existing have lasted 40 years. If it were not for the end lapsbuildings. The notched sub-purlin provides the most and the way these panels were through-fastened toattachment back to the structure; and when used the structure, they would have lasted a lot longer. Inover an R-panel, it will increase the load-carrying our view, coatings or single-ply re-covers are short- capacity of the underlying purlin. In essence, by term solutions when compared to a metal roof thatusing a notched sub-purlin, structural enhancement can last 50-plus years. We re-cover with full-length,is actually provided while the roof is being re-covered. structural standing-seam panels that are attachedWe re-covered 10 to 12 hangars and assorted back to the structure. outbuildings with the notched sub-purlin and double-During the past 12 years, the systems have evolvedlock panel and had 100-percent success with the as improvements have developed, but the basic ideasystem. We know it will be a watertight solution long is the same: leave the old roof in place, use full-lengthinto the future, Brown says. Coatings are temporary panels to eliminate the end laps, and attach the newfixes, and single-ply re-covers have a much shorter roof to the structure.life expectancy than metal. Both end up being more costly, so we wont go that route.When we first started re-covering buildings at theSYMMETRYairport, we used a notched sub-purlin attached through the old roof into the purlin below and a continuous- About five years ago, Brown was introduced to length,2-or3-in.-tall,vertical-rib,180-degree,a two-piece, mechanically seamed, symmetrical Continued on page 12www.mrca.orgMidwest Roofer 11'