Multiple problems, including an aging structure and a failing asphalt roof, led Bibb County, Ga. Schools to recover the roof of historic Alexander II Magnet School with a symmetrical standing seam metal roof.
The original building that housed the Alexander II Magnet School in Macon, Ga., was completed in 1902. Several significant additions through the years have brought the entire facility up to 41,650 sq. ft. In June 2000, Alexander II was named to the list of 11 Most Endangered Historic places by the National Trust for Historic Preservation.
“During an assessment, we discovered that the asphalt shingles were installed with no ventilation and heavy insulation,” says Jody Usry of Edifice Consulting in Byron, Ga., “It was designed for metal so with no ventilation, the shingles were burning up. And there was so much expansion and contraction that the nails were backing out in spots. The best thing to do was retrofit with metal.”
Combine this 0.75-in. airspace with vented eave and ridge material and you get a total uninterrupted air flow between the two roofs. Known as “above sheathing ventilation,” or ASV, this idea uses airspace to help reduce heat transfer. Testing at Oak Ridge National Laboratories (Tenn.) demonstrated how a free-flowing airspace between a metal roof and shingles could reduce heat transfer by 30% to 50%. Reducing heat transfer greatly reduces cooling costs, a savings for the building owner. During the winter months in colder climates, insulating airspace will also reduce the chance of ice buildup caused by heat transfer up through the roof. “There are a lot of trees around the school and the roof is subject to falling branches,” says Usry. “Installing a symmetrical panel allows for the removal and replacement of individual panels that sustain damage, including falling branches.”
Usry says there were flat roofing areas with an internal gutter that were recovered with new decking and sloped to allow water to flow to an external gutter. All internal gutters were replaced.
Modified bitumen was applied over existing modified bitumen at low slope areas after thermal scans were done to identify wet insulation.
McElroy’s 138T symmetrical standing seam system is a quick and efficient method for installing metal roofing directly over asphalt shingles, without an underlayment and without a tear-off. The system is designed around the patented clip paired with the company’s 138T symmetrical standing seam panel. Measuring 1.375-in. tall, it is a two-piece mechanically seamed metal roofing system.