Cover boards, like all components of a roof system, need to be compatible with the insulation, roof membrane and attachment methods. Attachment methods include hot asphalt, cold adhesive, bead polyurethane foam and spray polyurethane foam, as well as mechanical attachment.The method of attachment selected should be based on the roof-deck type, roof-system components, design requirements and the roof-cover type. Like insulation, the attachment of the cover board is critical to the system’s success. As with insulation, when cover boards are placed in an adhesive, they must be fully embedded in the adhesive and not just “stepped in” place. Instead, they must be weighted in until the adhesive is set. I specify 35-pound weight (the weight of a full 5-gallon adhesive can) at each board corner and in the center. Cover boards can cup and, if only stepped in place, will often cup upward out of the adhesive, resulting in a cover board and, ultimately, a roof cover that is not adhered and, therefore, susceptible to wind uplift.
Cover boards are an important and integral part of the roof system and when properly specified and installed will enhance the roof system’s ability to achieve a greater service life and reach sustainability. Cover boards’ use can now be considered good roofing practice.
Additional Information can be found in the NRCA Waterproofing Manual. Read articles by Dr. James Hoff, “The Sustainable Roof Cover Board”, Roofing Contractor, April 2015, and Jason Wilen, “Covering Your Options”, Professional Roofing, May 2014. Also, view various cover-board manufacturers’ product data sheets.
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