By Stan Choiniere Olympic Fasteners Agawam, MA ABSTRACT Traditionally, insulation has been attached to structural roof decks with either hot asphalt or mechanical fasteners Multi-layer insulation systems have also been bond¬ ed together with asphalt In the majority of cases, this is still true, however, a number of special circumstances may dictate that an alternate attachment method be used One such option is the use of urethane foam adhesives Stan Choiniere Stan Choiniere has over 20 years experience in the commercial roofing industry Technical Director of Olympic Fasteners, he has written numerous magazine articles on a variety of roofing topics He holds several patents, and has done extensive work on code approvals for adhesive technology products For several years, Choiniere has been a member of the board of directors of SPRI (Sheet Membrane & Component Suppliers to the Commercial Roofing Industry) and chaired SPRI’s Fasteners Subcommittee Choiniere—3
Traditionally, insulation has been attached to structural roof decks with either hot asphalt or mechanical fasteners Multi-layer insulation systems have also been bonded together with asphalt In the majority of cases, this is still true, however, a number of special circumstances may dictate that an alternate attachment method be used One such option is the use of urethane foam adhesives Urethane foam products can be modified for many different applica¬ tions Depending on the amount of rise, the foam can be used as an insula¬ tion as well as an adhesive Generally speaking, for adhesive applications, a low-rise foam product will be used The foam is available with a variety of delivery and application systems and they are either one- or two-component systems One-part adhesives are typically dispensed from low-pressure cylinders through a hose and wand system In some cases, they may be applied with a poured-in-place system The one-part products are moisture cure systems, using the ambient moisture in the air to kick off the curing process The speed of cure is dependent on the moisture in the air and the air tempera¬ ture Two-part adhesives, as the name implies, utilize two components that are pumped through a spray rig and mixed in a specially designed spray gun When the two parts are combined, a chemical reaction is initiated The amount of rise and the speed of cure can be controlled by modifying the catalyst Generally, the one-part products are applied in ribbons on the roof deck, or in the case of multi-layer insulation systems, to the base insulation board With two-part products and the spray equipment used with them, full coverage of the substrate is common With irregular surfaces, this can be an advantage Typical two-component spray unit. Typical application. The inherent advantages of using a urethane foam adhe¬ sive over bonding adhesives or cold-applied asphaltic prod¬ ucts include • The fast cure time provides high bond strength within 1 -2 hours vs days • The expanding nature of the foam will compensate for irregular bonding surfaces • There is very little odor, if any, when compared with asphalt of solvent-based adhesives, thus allowing for use in sensitive areas, such as schools, hospitals, and other medical care • The process reduces construction noise Many facili¬ ties are sensitive to noise and are unable to suspend business while roofing projects are being performed The use of mechanical fasteners, especially when pre¬ drilling is required, such as with concrete and gypsum decks, can create very noisy conditions Urethane foam adhesives have been used on many such projects to avoid interruption of business Choiniere—5 / • The ability to adhere directly to built-up roof systems with certain types of foam adhesives allows for the installation of a new roof without disruption of the old roof This further reduces the noise lev¬ els, eliminating disposal expenses and avoiding potential asbestos issues While not suggesting that structurally unsafe roof decks be left in place, there are instances where a roof deck may not be capable of holding a mechanical fastener, but may still be structurally sound Under these circum¬ stances, a urethane foam adhesive can be a very cost -effective and high-performance solution Adhesive applied in a beaded form. Depending on the specific product, urethane foam adhesive can be used to attach insulation to any type of roof deck and even directly to BUR roof covers Factory Mutual approves adhering to all approved substrates except steel and wood For multi-layer insulation over steel deck, the Factory Mutual-approved application is to mechanically attach the first layer of insulation and to bond subsequent layers This is especially effective with tapered insulation systems and also eliminates thermal bridges Again, approvals and compatibility are product-specific, but most types of rigid insulations can be used with urethane foam adhesive Systems using urethane foam adhesive have achieved very high wind ratings when follow¬ ing specific construction assemblies There are further safety issues to consider with urethane foam adhesives vs asphalt The most obvious is the fact that the urethane foam adhesive is not hot and will not cause bums Eye and breathing protection is recommended Two components: full coverage. while applying urethane foam adhesive Some city ordinances prohibit the use of hot asphalt, and Department of Transportation (DOT) regula¬ tions are making the transportation of kettles more difficult Getting the product to the roof is also easier with urethane foam adhesive Even products that use spray equipment are much easier to use, especially as building height increases Urethane foam adhesives are not the solution for every project They are not the most cost effective option on steel decks, nor are they Factory Mutual approved direct-to-steel But when comparing to labor intensive applications such as pre-drilling and fastening to gypsum decks or dealing with hot asphalt on a concrete, urethane foam adhesive becomes a very effective alternative Choiniere—6
