Retrofit Report: Butler reroof keeps printing plant weathertight
by Jonathan McGaha | 26 April 2011 12:00 am
Harry Hostetter Jr. watched roof leaks in the Henry Wurst Printing Plant in North Kansas City, Mo., become steadily worse over nearly half of his 31-year career at the facility. By the time he became the maintenance manager, the problem was most pronounced along a 100-foot long valley gutter created between additions to the facility in 1965 and 1967 that doubled the size of the 86,000-square-foot printing plant.
The gutter was installed before the use of stainless steel to fabricate them and corrosion had advanced steadily as the metal roof eventually exceeded its expected 15-year life. However, surface rust, pinhole leaks and loose screwbolt fasteners across the corroded roof’s 26-gauge steel panels were minor annoyances compared to the severely corroded gutter down the juncture of the two adjoining, double-slope metal buildings.
“We had patched it repeatedly as the gutter rusted through and the leaks grew increasingly worse over the years,” he says. “The valley extended over an area for finished product and some electrical boxes, an intolerable risk. We also suffered finished product losses on several occasions. It got so bad that we kept 55-gallon drums in the plant to catch the water and made that a priority for people working at night during the heavy storms we can get in Kansas City.
“We had several roofers come out and price various fixes in recent years. We considered coatings, membrane overlays and even thought about building the roof up to a flat profile over the valley. Finally, one of the roofers asked about the load rating of the structure which prompted Hostetter to contact [Liberty, Mo.-based] Billings Construction Co., a Butler Builder [for Butler Manufacturing, Kansas City] serving this area. This set things in motion for a permanent solution.”
Some initial concern about the building’s strength to support additional weight imposed by the roof retrofit was resolved by a Butler roof engineering expert who researched the strength of the Z purlins used for roof support during the time of original construction in the 1960s.
After reviewing historical design records, Butler confirmed that the yield strength of the steel Z purlins used in the 1960s was 55 ksi rather than the 33 ksi presumed by an outside engineering consultant engaged by the printing company. The bearing strength of the purlins used in the 1960s would accept the additional weight of the reroof using the Butler 26-gauge MR-24 standing-seam metal roof system underlaid with 3 inches of unfaced fiberglass insulation. Moreover, the completed retrofit would have a 7-pound-per-square-foot safety factor.
“Billings Construction was also able to perform the work from February through early March 2009 while the space below remained in full operation,” Hostetter says. “That was especially important to us.”
The initial 425- by 100-foot metal reroof covered the entire length of the valley and closed in some ridge vents and unneeded penetrations. The new roof extends between the parallel ridgelines of the plant’s original, double-slope profile. The reroofed section’s 1/4:12-inch positive slope drains toward each side onto the remaining original roof rather than down a valley condition. As additional funds are available to reroof the balance of the two adjoining buildings, the 12-inch-high gap fitted with temporary metal closures created down the length of the old and new metal roof will be removed and an expansion joint added to create a stepped condition along the recent retrofit roof’s juncture with the existing roof.
“This was not the cheapest approach but it offers a permanent fix,” Hostetter says.
Heavy snowfalls in 2009 and Midwest thunderstorms that swept Kansas City in early 2010 thoroughly tested the weathertightness of the reroofed section. Hostetter notes that not a drop reached the plant operations area beneath the new roofing.
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For more information on Kansas City, Mo.-based Butler Manufacturing, visit www.butlermfg.com.
Source URL: https://www.metalconstructionnews.com/articles/retrofit-report-butler-reroof-keeps-printing-plant-weathertight/