SBS Modified Bitumen - Page 5

7A.12.5 Another application technique, called "mop and flop", is frequently used in the western portion of the United States. The modified bitumen sheet is cut to short lengths, usually between 12 and 16 feet (3.66 and 4.88 m) long. It is placed upside down, adjacent to the roof area where it will be installed, along the laying line of the preceding course. The entire area to be covered by the sheet is then mopped with hot asphalt, as well as the lap area of the upside down sheet. Mechanics then pick the sheet up by the ends and "flop" it, right side up, into the hot asphalt, making certain to align it with the asphalt line created by the sheet itself. Again, brooming the sheet and scuffing the lap are recommended.

7A.12.6 Polyester reinforced SBS modified bitumen sheets should be unrolled and allowed to relax. Rerolling or scrolling of the sheet is then employed to set the sheet. The "mop and flop" technique is not acceptable for polyester reinforced SBS modified bitumen sheets.

7A.13 Mechanically Applied Asphalt

7A.13.1 The asphalt can be applied using a mechanical asphalt spreader, which can increase productivity. Some contractors have found that installing the material with a felt layer can also improve production.

7A.14 Cold Adhesive Application

7A.14.1 There are situations where the use of hot asphalt is undesirable or prohibited. In such cases, it may be necessary to use alternative materials such as cold adhesives (typically referred to as "cold process cements" or "cold application cements/ adhesives"). JM’s Research and Development staff has determined that traditional cut-back asphalt mastics, as well as some of the newer "modified bitumen adhesives", can have an adverse effect on SBS modified bitumen products. This is due to the very high levels of solvent used in most of these products. Softening, blistering and excessive granule loss can occur as the solvent passes through the membrane. This can cause accelerated aging of the underlying waterproofing with the potential for premature membrane failure.

7A.14.2 Through the evaluation of numerous alternate adhesive systems, JM has developed two viable cold application systems for use with SBS modified bitumen products.

7A.14.3 First, there are two unique premium-grade, two-part adhesives. These products have extraordinary physical, adhesive, and waterproofing properties, and are compatible with both SBS modified bitumen products and with conventional asphaltic materials. These products are MBR Bonding Cement, for the field of the roof, and MBR Flashing Cement, a trowel-grade cement, for terminations, base flashing, and penetration (pitch) pans. Both adhesives require mixing of two components immediately prior to application. MBR Bonding Cement is available in pails containing 4 1/2 gallons (17.0 liters) of base material, and MBR Flashing Cement is available in pails containing 4 gallons (15.1 liters) of base material. The pails are large enough to accommodate the addition of approximately 1 pint (0.47 liters) of MBR Cement Activator and the necessary mixing process.

7.14.4 Second, there are two mastic-type, one-part adhesives.  These materials are compatible with SBS modified bitumen products. They contain very low levels of solvent, about one-third of that found in most traditional roofing mastics. These adhesives are elastomeric and have good waterproofing properties, and, over time, develop adhesive properties that exceed those of traditional mopping asphalt. These products are MBR Cold Application Adhesive for the field of the roof, and MBR Utility Cement, a trowel-grade cement, for terminations and base flashings.

7A.14.5 For more information on these cold application products, refer to the "Products" section of the current JM Commercial/Industrial Roofing Systems Manual.

7A.15 Health and Safety

7A.15.1 JM develops and maintains Material Safety Data Sheets (MSDS) for all of its products. These MSDS contain health and safety information for development of appropriate product handling procedures to protect the users of our products. These MSDS are available through the Product Information Center, 1-800-654-3103, via Fax Express^®, 1-888-329-3977, or on the JM website, www.jm.com, and should be read and understood by all involved personnel prior to using and handling JM materials. In addition to the MSDS, JM products have health and safety precautions printed on the product label or packaging. The user is strongly urged to familiarize himself with this information prior to using the product, and observe certain precautions during use.

7A.16 Two-Part Cold Adhesive Application

7A.16.1 MBR Bonding Cement can be used as a direct substitute for Types III and IV asphalts used in hot asphalt specifications. The adhesive is mixed on site and applied by squeegee or spray techniques. Subsequently, JM felts and modified bitumen sheets are laid into the bed of adhesive. The adhesive will set within 20 to 40 minutes, depending on temperature, holding the modified bitumen sheet in place. It will cure in 2 to 4 hours into a tough, durable, and highly weatherable rubber film. Partially-adhered specifications are not recommended with this material.