Cover Boards: The Membrane and Insulation Protector

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Posted By: Thomas W. Hutchinson, AIA, CSI, Fellow-IIBEC, RRC September 21, 2015

ATTACHMENT METHODS

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.

Glass-mat-faced gypsum boards can be mechanically fastened and set in various adhesives. In the photo, the cover board is mechanically attached and set in bead polyurethane foam and hot asphalt. PHOTO: Hutchinson Design Group

Glass-mat-faced gypsum boards can be mechanically fastened and set in various adhesives. In the photo, the cover board is mechanically attached and set in bead polyurethane foam and hot asphalt. PHOTO: Hutchinson Design Group

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.

GOOD PRACTICE

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.

Learn More

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.

MORE FROM HUTCH

“Roofs Are Systems”, January/February 2014, page 52
“Roof Decks”, March/April 2014, page 54
“Substrate Boards”, July/August 2014, page 52
“Vapor Retarders”, September/October 2014, page 52
“Insulation”, November/December 2014, page 50
“Wind-damaged Roof Systems”, January/February 2015, page 60

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About the Author

Thomas W. Hutchinson, AIA, CSI, Fellow-IIBEC, RRC
Thomas W. Hutchinson, AIA, CSI, Fellow-IIBEC, RRC, is principal of Hutchinson Design Group Ltd., Barrington, Ill., and a member of Roofing’s editorial advisory board.

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1 Comment on "Cover Boards: The Membrane and Insulation Protector"

  1. Drew Harrison | September 22, 2015 at 9:50 am | Reply

    Efficiency is something that is really important to me. A lot of people take it for granted until it’s gone or live somewhere with poor insulation. Getting the right layer can literally save you a ton of money on your heating bill when the time comes. Thanks for bringing this up and great tips!

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