b'ARCHITECTURAL SHEET METALContinued from page 11metal panel. It was not hard to see it had significantOn this job, we had a couple of challenges, Brown advantages over the double-lock system we hadsays. First was meeting the wind loads on a barrel been using, he says. (See Figures 2 and 3.) First,vault with 5-ft. purlin spacing in a 110-mph wind a symmetrical panel can provide better wind upliftzone. The corner pressures per ASCE-7 were -78 capacity over existing frame spacing, and that is verypsf. Second was dealing with a transition between important here in southern Louisiana. Also, the seamthe barrel vault roof and the adjacent shed roof. design on a symmetrical panel is more watertightThis transition has been a failure since it was first than a double lock because there is no interruptioninstalled; and over the years, several unsuccessful of sealant in the seam at the clip locations. Mostrepair attempts had been made. By using an extra-importantly, a symmetrical panel can be easily fixedhigh-notched purlin, we were able to create a 5-in. if there is ever damage or a reason to pull a paneldrop from the curved roof onto the transition flashing; out of the roof at a later date. In this hurricane-proneand by using 100-percent continuous clips with the area, the idea of being able to replace an individualsymmetrical panel, we were able to meet the FM-panel anywhere on the roof after a storm carryingdetermined wind loading. (See Figures 4 and 5.) flying debris is a very big plus.Responsible spenders keep an eye on their budgets, Symmetrical standing-seam systems do not haveand the Lafayette Regional Airport is a responsible male and female seams but are comprised of panelsspender. On a recent inspection, Brown became with matching left and right seams. The panels areaware of leaking issues on three rows of T-hangars. It joined with a mechanically seamed cap. The panelswas a familiar problem: an exposed fastener R-panel are nondirectional, meaning they can be installedthat had endured too much Louisiana rain, heat, and left to right, right to left, or even from the center out.sunshine. AD HEREAround the same time, the Airport Authority switchedAs we had done so many times before, we proposed insurance carriers to Factory Mutual. This requiredinstalling a notched sub-purlin system to re-cover the the use of FM-approved systems, along with havingT-hangar roofs, Brown says. Everyone was familiar a professional engineer design the recover. The mostwith the system and knew it worked. We were a little recent re-cover with a sub-purlin installation wassurprised when we were told the budget did not allow topped with an FM-listed 16-in. curved symmetricalfor another notched sub-purlin re-cover.panel with 100-percent continuous clips over a 5-in.- Discussion came back to removing the original R-panel tall, notched sub-purlin system. The system met FMand replacing it in kind, but that would require the 1-195 approval for that construction method. building to be cleared during the installation of another R-panel. This method would not be popular with the tenants, but it would be an affordable solution, and it could be done within the airports budget.Figure 4Here, a 5-in.-tall Roof Hugger retrofit purlin anda130-ft.-longcurvedsymmetricalpanelwith 100% curved continuous clips were used to solve the problems of wind uplift and leaky transition.Figure 5Finished application showing continuous panel, step-down, and welded stainless flashing.Continued on page 1412 www.mrca.orgMidwest Roofer'