Q: Why does it seem that there are so many moisture-related problems with flooring installations in surgery rooms and schools?
A: I’ve seen moisture-related problems in an operating room where no problems were evident in the corridors outside. The reason? The temperature and humidity levels in the operating room are different than those in the corridor. Because the driving force of moisture vapor movement is temperature and humidity, the moisture movement is greater in the operating room. Often, in a school environment, temperature and humidity are allowed to fluctuate in the structure. When school is in session, the temperature and humidity controls are activated. But whenever the school is not being used -- during nights, weekends and holidays -- the temperature and humidity controls are turned down to conserve energy. The effect is fluctuation in moisture vapor movement.
Q: How thick does a cementitious underlayment have to be to serve as a barrier coat that prevents discoloration due to the adhesive’s effect on vinyl-backed sheet goods?
A: Many installers feel that a thin skimcoat will suffice as a barrier. Not true! A barrier coat must be just that -- a barrier. If a barrier coat is to be effective in the prevention of plasticizer discoloration, it must be a minimum of 1/16-inch thick. To render the skim coat porous, the layer would have to be 1/8-inch thick.