NEW LIFE FOR AN OLDER SCHOOL

Central Lee Community School District administrators made a bold decision to upgrade the district’s high school. Located near Donnellson, Iowa, the major renovation ended recurring roof leaks, dramatically improved its energy efficiency and upgraded the facility in other ways that will benefit students — and even some adults — for decades. The high school is now equipped with improvements and technologies to efficiently serve its mission well into the 21st Century.

The upgrade program initially focused on replacing the roof for the second time since the facility was built in 1962. The first replacement had applied a single-ply system that was again showing signs of advanced deterioration. This led the district administrators to approve a more durable, standing-seam metal roof system of the type that is specified increasingly on schools. The plan was to install the new standing-seam metal roof over the top of the existing roof without disrupting the use of the classrooms. Unforeseen conditions, however, required an innovative engineering solution as soon as the crews embarked on the work.

“We were not sure the roof could make it through another year,” recalls the former Superintendent Joe Crozier, now with another district.“There were lots of leaks, and the old membrane was actually pulling away from the edges.”

The project scope steadily increased with the availability of funds. In addition to the MR-24 standing-seam metal roof system, the project brought insulation values in the roof up to R-40 and R-19 in the walls that were reclad with a new metal panel system. Other energy-related improvements included thermal-insulated replacement windows, an energy-efficient lighting system and an advanced air-conditioning system. The new lighting and total-electric geothermal heat pump system qualify the district for a generous utility rebate program. The addition included a 10,500-sq.-ft. classroom building wired with fiber optic cabling to support a computerized learning center and satellite-transmitted adult education programs. Finally, the campus received a 60-space parking lot and a 30-ft. by 40-ft. Ag Shop finished out by students as a class project.

To facilitate the complex project delivery, the district hired the Des Moines-area office of Septagon Industries, based in Sedalia, Mo., to serve as the construction manager. Others on the team included SVPA Architects, Inc., of Des Moines, as project architects, and S.G. Construction Company, Inc., based in Burlington, Iowa, whose contract covered the roof replacement and other metal building systems installation. Butler Manufacturing Company supplied engineering services and the metal building systems products applied to the project.

The original plan was to convert the existing flat roof into a double-sloped profile with a positive pitch for improved drainage. Workers began to strip off the gravel ballast from the existing single-ply membrane prior to installing the subassembly for the metal roof. Their progress was scuttled when the existing roof material became much thicker than indicated on the drawings supplied for the building.

Instead of the anticipated six in. of pre-existing roofing material, the crew discovered 14 to 16 in. of Styrofoam at some points across the center of the roof. The insulation barrier had been significantly increased during the previous roof replacement but the drawings were never updated to reflect it. These conditions brought things to a standstill because the depth of the existing roofing exceeded the longest fasteners used for the work. Furthermore, the prohibitive cost to remove and dispose of the excess roof material would have disrupted continued classroom use. The situation dictated a comprehensive re-engineering of the project, a Septagon spokesman says.

The project team quickly huddled engineers within the Roof Group of Butler to develop an alternative approach. The engineers recommended superimposing“piggyback” framing over the original structurals of the building. This would provide a clean support assembly for the new standing seam metal system and eliminate the need to tear off the old roof. After a two-month delay, the work finally began in December.

The crews stripped off the gravel ballast and cut openings as they advanced through the existing roof materials. Three-in.-square vertical pipe columns were welded directly to the beams above the building’s support columns.

“Around 200 pipe columns were required,” recalls Ron Massner, vice president of S.G. Construction. “First, we had to cut through the insulation, then through three in. of the original roof.”

Everywhere a building column existed, the crew drilled an exploratory hole down through the roof to accept a pipe member for the piggyback framing. As each exploratory hole was created for a pipe column, it was temporarily patched to prevent leaks pending the installation of the pipe member and the subsequent standing-seam metal roof assembly. The holes were enlarged just enough later to accept the pipe columns as they were welded into place.

Galvanized tin caps were put into place temporarily to prevent moisture intrusion until installation of the new metal roof. The decision to reroof the building came none too soon, the district discovered. Although it was a mild winter, the temperature dropped one day, and an 80-ft. crack appeared along the old thermoplastic membrane. The crews scrambled to seal it before the onset of forecasted sleet and rain.

With the piggyback framing in place, purlins were set into place and received the preformed metal panels of the MR-24 roof system. The edges were seamed together using a proprietary electric rollformer that traveled the edges of the panels, creating the same type of seam used to seal canned beverages. A series of clips bolted at prescribed intervals are seamed into the edges during the process. The clips have an engineering provision that accepts thermal-induced expansion and contraction movement caused by temperature changes.

Despite the delays and added work of installing the piggyback framing, the workers completed the reroof in about two months — on schedule. The balance of the work added new life — and appearance — to an older school that is again a wellhead of community pride.

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