For some time, NRCA has been investigating moisture in lightweight structural concrete roof decks and made recommendations in August to its membership regarding the use of such products. If you are involved in the design or installation of roof systems on concrete roof decks, you should be aware of these moisture-related concerns.
Since 2009, NRCA has received a significant number of reports of moisture-related problems associated with lightweight structural concrete roof decks. Problems include moisture accumulation, loss of adhesion of roofing layers, adhesive issues with water-based and low-volatile organic compound adhesives, metal and fastener corrosion, and insulation R-value loss.
Rene Dupuis, president of Structural Research Inc., Middleton, Wis., and I presented a paper at the 2011 International Roofing Symposium that discussed the high moisture content and humidity present in lightweight structural concrete roof decks four to seven years after placement. Roof system performance issues related to the roof decks' moisture was noted in each of the projects studied.