PROSOCO and the O.T. Hogan Biological Science Building
While they studied biology on the inside, they battled it on the outside.
The O.T. Hogan Biological Sciences Building, Northwestern University, Evanston, Ill., hosts the school’s Interdepartmental Biological Sciences Graduate Program, and a host of other biological, medical and neuroscience studies.
Designed in 1967 by Walter Netsch, the six-story “Brutalist” building features fluted limestone walls and vertical aluminum window bands. By 2009, it also featured a black tide of stone-eating mold slowly growing down from the building’s upper reaches.
“Heavy organic growth, especially on the top two stories” is how Mark Larose, JSL Restoration, Franklin Park, Ill., assessed the staining. JSL Restoration was tapped to eradicate the expanding black colonies as part of an overall restoration of the building exterior by Triumph Restoration, Mokena Park, Ill.
The project included sealant and window replacement, and cementitious and Dutchman repairs to the stone.
“It was deeply embedded,” Mr. Larose said of the organic growth. “It also protruded from the stone 1/16th to 1/8th of an inch. “You could see the spores,” he said. “They looked hairy.”
Mr. Larose saw the mold up close, from swing stages anchored to the top of the building.
“It smelled like seaweed when we cleaned it,” he said.
Black mold like that on the O.T. Hogan Building doesn’t just stain the stone. It also increases water absorption by penetrating the stone’s veins. That causes honeycomb weathering damage to the stone, according to www.inspectapedia.com. The site is an on-line encyclopedia for building and environmental inspection, testing, diagnosis and repair.
As Triumph Restoration wrapped up their repairs in September 2009, the JSL crews got to work.
Working from the bottom of the building up, they applied Enviro Klean® BioWash® with automatic sprayers. The job took four crews who traded off between rigging the swing stages and cleaning the stone.
Mr. Larose said they chose BioWash® for the job because of its combination of effectiveness as a cleaner and its mildness. BioWash® won’t harm plants and requires only minimum safety precautions and gear – a plus for use on a busy, green campus.
Nevertheless, the JSL crew used enclosed canopies to shield passersby from the spray of pressure-washers during the work.
They diluted one part cleaner to one part water for the less-heavily stained lower parts of the building, according to JSL Project Superintendant Kevin Jendras. They saturated the dry surface, achieving a 6-inch rundown, then agitated lightly with soft-bristle brushes.
The techs let the scrubbed-in BioWash® do its work over a 15-minute dwell, then pressure-washed away the spent cleaner and the mold it removed. The crewmembers had to pressure-wash a little more slowly than usual to make sure they got into the recesses of the uneven, fluted surface, Mr. Larose said.
Where the mold ran rampant at the building top, the JSL crew simply hit it with undiluted BioWash® – twice.
“The BioWash® worked great, even on the heavy staining,” Mr. Larose said.
Even going slowly, the crews reclaimed about 2,000 square feet a day from the mold.
In all, the JSL team cleaned more than 48,000 square feet of limestone by the time they finished in October.
They’re still studying the biological sciences inside the O.T. Hogan Biological Sciences Building, but the battle for the exterior is over.
And the good guys won.
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