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March 16, 2006
Contact: Lynn Bretz, University Relations, (785) 864-8866.

Force of microburst wind pressures wrought havoc on KU campus roofs

Dyche Hall. View photo gallery.

LAWRENCE — The sudden positive and negative wind pressures created by Sunday’s microburst over the University of Kansas campus caused extensive roof damage, officials said today.

The high wind, up to 80 miles per hour, created positive wind pressure on one side of a building and negative pressure as it flowed over the opposite side, said Jim Modig, director of design and construction management at KU. Together, the competing pressures lifted roofing materials, in some cases tearing them off and in others slamming the roofs back down, he said.

Some of the battered roofs cannot be repaired and must be replaced. Others suffered significant damage to membranes, decking, shingles and tiles. About 60 percent of the Lawrence campus buildings sustained some form of damage from the storm, and the university is continuing to inventory the full aftermath. Preliminary estimates put the cost of repairs at between $6 million and $7 million.

Buildings whose roofs must be completely replaced include Computer Services Facility, Blake Hall, Danforth Chapel, Parker Hall (part of the Kansas Geological Survey complex) and Gertrude Sellards Pearson residence hall. The section of the Robinson Center roof over its basketball courts must be replaced. Other buildings with significant damage include Art and Design, Dyche Hall, Fraser Hall and Twente Hall. The buildings are safe to be occupied and are otherwise structurally sound.

Most of the damaged roofs were installed five to 10 years ago, Modig said. Roofs that were installed within five years suffered less damage.

Modig said campus buildings have two basic types of roofs — tile and flat roofs — and both are designed to withstand normal Kansas weather conditions.

“No roof is bullet proof,” Modig said. “If you expose it to conditions in excess of what it was designed to withstand, it will fail.”

The tile roofs, such as those found on Dyche, Fraser, Stauffer-Flint and Snow halls, have fired red clay tiles covering the tops of the buildings at a significant slope. A nail through a hole in the tiles attaches them to the surface below. When the microburst struck, the wind began to lift the tiles. Some nails were pulled out completely, and others were pulled out only partially. The partially pulled tiles were then either stuck or slammed back down against the roof surface.

Modig compared the tiles slamming against the roof to “banging a plate against a table” and many of the tiles broke and flew off the roofs.

The flat roofs on campus have two variations — ballast and directly adhered. The ballast has a membrane that covers the roof to keep moisture out and is held down by a paving system. For example, a concrete paving system holds down the Wescoe Hall roof membrane, which sustained minimal damage.

Directly adhered or mechanically fastened roofs have a vapor layer and an insulation layer topped by a roofing membrane, which is adhered by tar or glue or mechanically fastened.

The sucking effect of the positive and negative wind pressures from the microburst on Sunday inflicted similar damage to flat roofs. It began to pull up membranes and their adhesion or paving system. When this occurred, the structural integrity was lost. Much of the material was slammed back down but is no longer securely fastened.

Temporary membranes have been installed on damaged roofs to keep moisture from getting into the buildings. Another high wind could compromise the temporary roofs. The membranes will keep buildings dry until permanent repairs can be made.

Modig said campus damage would have been much worse if the storm had been accompanied by rain. Moisture would have entered buildings through the damaged roofs, with the potential to cause extensive damage to the interior of buildings.

“We’re very, very fortunate we didn’t get any rain,” Modig said.

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The University of Kansas is a major comprehensive research and teaching university. University Relations is the central public relations office for KU's Lawrence campus.

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