Hail has made its’ presence felt more and more in recent years in the Luna & Associates regions, even causing damage to typically hail resistant commercial projects. Some damage is fairly evident, and readily identified such as cuts to membrane, dented units and edge metal. Another form of damage sometimes isn’t as obvious. This would be delamination of the roofing membrane from the insulation in an adhered roofing system. This type of damage starts in small areas where hail has broken the facer and left an un-adhered void. These small voids can grow with each successive wind event and cause large delamination, years after the hail storm that initiated it. Typically this phenomenon develops when the assembly does not include a cover board.
In response to this damage, roofing manufacturers have started to offer hail coverage in their warranties. In general this warranty coverage is a good benefit to the building owner. As always, the best insurance against damage is a good design. When designing for potential hail storms designers should take the following steps:
- Use a cover board of at least ½” in thickness. Thinner cover boards have been shown to break when hit by hail. High density
polyisocyanurate products such Carlisle’s Securshield HD perform very well in this role. - Secure the top layer of cover board in adhesive. Do not mechanically attach it. Hail will split the membrane if it hits the plate
or fastener. Low rise adhesives, such as Carlisle’s Flexible FAST, are specifically designed to provide cushioning and allow for
building movement while still keeping tenacious holding power on the insulation and cover board. - Utilize a thicker membrane such as a 90 mil EPDM, 80 mil TPO or 80 mil PVC. Testing has shown that externally reinforced
membranes commonly referred to as FleeceBACK membranes, perform the best of all available membranes in this role. The
slight increase in membrane thickness provides an immense increase in puncture performance.
Be wary of those who want to “Value Engineer” out one of these steps and still offer a hail warranty. When all hail breaks loose on one of your projects, will you have more faith in the warranty to replace the damaged roof system for your client or the good design that you followed to prevent the damage in the first place?
As always, please contact your local Carlisle rep if you have any questions or would like to discuss in further detail.
