Patent Publication Number: US-7712275-B2

Title: Method for reducing roof membrane damage from hail/fastener contact impact and a roof system having reduced membrane damage from hail/fastener impact

Description:
BACKGROUND 
   In the roofing industry and particularly the commercial roofing industry, exposed roofing membranes have become prevalent. Single ply roofing systems, and others using an exposed membrane, although very effective are subject to greater damage from hail impact than some other types of roof systems. One significant exacerbator of the potential for damage from hail is the very fasteners that retain the membrane and roof assembly component materials underlying the membrane. Such fasteners are nails, special clips, anchors or screws and typically have washers positioned thereunder to spread the hold down load of the head of the fastener. Because fasteners are generally immovable, connected to structural subjacent roof support materials or otherwise substantially immoveable, they pose particular risks to the overlying waterproofing membrane when hail strikes. The fastener/washer act essentially as an anvil against which the roofing membrane can be suddenly and violently compressed by the substantial momentum transfer from a hail stone. This compression tends to rapidly and for short duration “flow” the membrane material in all directions from the impact site. Rupture of the overlying waterproofing membrane can easily occur when hail hits the membrane in an area of an underlying fastener. In order to improve the hail resistance of such roof structures, this characteristic must be alleviated. The roofing industry tests for hail presently utilize a ½″ to 2″ steel ball. The ball is accelerated to terminal (free full) velocity and directed at a roof assembly to measure hail impact. Recently, hail testing has been developed further to enable the shooting of actual ice balls from an air cannon through a timing device at a roof assembly which has been cooled to 38° F. with chilled water. This test more realistically shows the effects of various size hail ice balls from ½″ to 5″ diameter at various mph speeds into a roof assembly sample. A 3″ hail ball approximately the size of a baseball will fall in still air at 95 to 97 mph. If the 3″ hail is caught in a down draft of wind it can increase its speed. Some 3″ hail impact dents on sheet metal equipment on roofs hit by hail required a 3″ hail ball to be shot at 150 mph to replicate the dent. At 100 mph, a 3″ hail ball will go through ½ inch APA approved oriented strand board (osb) wafer board and at 135 mph and a 3″ hail ball will go through ½″ plywood. 
   SUMMARY 
   Disclosed herein is a method for reducing roof membrane damage from hail/fastener impact by locating a fastener, positioning an energy absorbing material over said fastener and affixing said material to said fastener. 
   Further disclosed herein is a roof system with reduced hail/fastener impact damage characteristics. The system comprises a roof substrate having one or more layers of material at least one fastener exposed at a top surface of said substrate and a dedicated energy absorbing material positioned over said at least one fastener. A roof water proofing membrane is placed atop the foregoing elements. 

   
     BRIEF DESCRIPTION OF THE DRAWINGS 
     Referring now to the drawings wherein like elements are numbered alike in the several Figures: 
       FIG. 1  is a schematic cross-sectional elevational view of a fastener in a representative roof assembly with a dedicated energy absorbing material thereafter; 
       FIG. 2  is a top plan view of the fastener and energy absorbing material; and 
       FIG. 3  is a schematic cross-sectional elevational view of an alternate embodiment of the  FIG. 1  embodiment. 
   

   DETAILED DESCRIPTION 
   Referring to  FIG. 1 , one of ordinary skill in the art will recognize the schematic representation of a roof assembly  10  comprising simply for purposes of illustration, insulation  12 , cover board  14  and a roof waterproofing membrane  16 . A fastener  18  is illustrated extending through board  14  and insulation  12 . Fastener  18  includes a head  20  and is employed in one embodiment with a washer  22  to spread the hold-down load on the cover board  14 . In the method disclosed herein, locating a fastener  18  is intended to encompass, at least, placing a fastener in the roof assembly or finding a fastener already in the roof structure, regardless of who put it there or when. Once fastener  18  has been located, whether or not the specific fastener employs a washer (washer embodiment is illustrated). Energy absorbing material, which as illustrated is two layers  24  and  26  but may be more or one layer if desired, is/are disposed over fastener head  20  and washer  22 . As illustrated, it is noted that layer  24  is large enough in perimetral dimension to cover only fastener head  20 . Layer  26  then is dimensioned to cover layer  24  and washer  22 . It will be understood that each layer  24 ,  26  could be large enough in perimetral dimension to cover both fastener head  20  and washer  22  if desired. 
   The energy absorbing material may comprise ethylene propylene diene monomer (EPDM), butyl rubber, EPDM with a butyl gum rubber bottom or other flowable material as a combination including at least one of the foregoing, and in one embodiment is affixed to fastener head  20  and washer  22  by adhering. The adhering may be by applying an adhesive material to the fastener head/washer or to the energy absorbing material during installation of the energy absorbing material, or may be simply by sticking down (self-stick) the energy absorbing material having had an adhesive pre-applied thereto. 
   It is to be understood that the roof structure illustrated in  FIG. 1  is only for purposes of illustrating an environment in which the method and system disclosed herein is employed and that other and different roof assemblies are equally benefited by the method and system described herein. In addition, although  FIG. 2  illustrates a rounded perimetral shape of the energy absorbing material, other shapes such as square, rectangular, triangular, oval, polygonal, etc. are acceptable substitutes providing at least the head  20  of fastener  18  is covered and in one embodiment both head  20  and washer  22  are covered. 
   In an alternate embodiment hereof, the energy absorbing layer(s) may be placed on top of the waterproofing membrane directly over a fastener instead of being applied directly to the fastener with similar beneficial results. This is illustrated in  FIG. 3  with all similar elements from  FIG. 1  carrying identical designations and the energy absorbing material carrying similar designations but bearing the alpha character “a” as a postscript. 
   While preferred embodiments have been shown and described, modifications and substitutions may be made thereto without departing from the spirit and scope of the invention. Accordingly, it is to be understood that the present invention has been described by way of illustrations and not limitation.