Troublesome Issues in the Roofing Industry Can Be Corrected with Knowledge and Proper Detailing

Polyurethane foam must be in contact with the insulation boards to be effective.

Polyurethane foam must be in contact with the insulation boards to be effective.


Roof Warranty Wind Speed Coverage Confusion
With the recent spate of landfall hurricanes, I undoubtedly will receive calls from attorneys looking for warranty coverage restitution. Many times, these attorneys and the owners they represent haven’t looked at the warranty coverage, which if not dictated is 55 mph. However, attorneys will say the local code requires design to wind speeds of 115 mph. Unfortunately, designers often do not realize there is no correlation between the design wind speed and what is covered by the warranty. This causes a great deal of consternation for building owners who assume their buildings are covered up to the wind design speed. Roof systems can be designed for high wind speeds but they require specific detailing and specification. To add to the confusion, even if you have wind warranty coverage to 102 mph, for example, once a tropical depression is declared a hurricane, the warranty is void; damage resulting from hurricanes is excluded under the terms and conditions of the warranty.

My recommendation would be to design the roof to meet the anticipated wind-uplift pressures resulting from the design wind speed. Detail roof edges and impinging architectural elements with robustness and redundancy to resist the pressures. If wind speeds greater than the standard 55 mph are desired, they need to be called out in the specifications. This might be a good opportunity to consider designing a resilient roof system— one that can weather the storm with minimal damage and be brought back into service quickly so the building can operate, which is increasingly important for critical facilities, such as hospitals, police, fire and transportation facilities. It also is important to recognize that power might not be available for roof repairs; consider a roof cover that can be repaired without power.

Lack of Adhesion Between Polyurethane Adhesives and Insulation Boards
In the Midwest, full-cover spray foam or bead foam adhesive is taking over for asphalt as the adhesive of choice. Foam adhesive is an excellent choice. It sticks to everything: cars, skylights, clerestories, or even your sunglasses.

A recent rash of court cases in which I’ve been the expert witness confirms the lack of understanding in regard to the application and embedment of insulation in the foam adhesive. Contrary to what many believe, you cannot just “blow and go”; in other words, place the adhesive, drop the insulation board and move on to the next one. (Doing this ensures I have future work!) It is amazing how many insulation boards go down and don’t touch the foam. If the insulation doesn’t touch the board or only slightly does so, wind uplift will remove it for you. Additionally, if the boards are not tightly compressed together, an air gap exists through which air—often moist air—can move and condensate within your roof system. That’s not a good condition either. You must specify that the boards need to be set in place with tight joints, walked on and then weighted in place until set. My firm specifies five 35-pound weights (5-gallon pails filled with water)—one at each corner and one in the middle—for 10 minutes. Yes, you need to be that specific.

If insulation boards are not tightly compressed together, an air gap exists through which moist air can move and condensate within your roof system.

If insulation boards are not tightly compressed together, an air gap exists through which moist air can move and condensate within your roof system.

The Designer’s Standard of Care

With roofing materials at an equilibrium, it falls to the design and construction industries to assemble roof system components in a cohesive, holistic manner. It all starts in the designer’s office. Providing little attention at that level, not understanding building sciences and dynamics, or foregoing proper detailing will lead to early failure.

Assuming the roofing manufacturer is the de facto designer and will correct your errors is an incorrect assumption. Assuming the roofing contractor will make it right in the field is an incorrect assumption. As the educated design professional, your standard of care is to continuously educate yourself to the ever-changing building envelope realm. Not knowing is not an excuse. Think about and understand the conditions you have created. Think about how the building’s interior function will affect your design. Think about constructability, the time of year when the parts will come together (as I write, it is 21 F outside and water-based adhesive won’t come out of the pail). Then, detail, detail, detail. Draw your details large: 3 inches equals 1 foot. Draw your details to scale; show all components; and understand how they are all interrelated.

Today’s troublesome issues in the roofing industry don’t have to be troublesome issues if you don’t let them occur.

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About the Author

Thomas W. Hutchinson, AIA, FRCI, RRC, CSI, RRP
Thomas W. Hutchinson, AIA, FRCI, RRC, CSI, RRP, principal of Hutchinson Design Group Ltd., Barrington, Ill., has more than three decades of experience in the roofing industry.

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