Cold Weather Application Recommendations for Modified Bitumen Roofing

Introduction
The application of any roofing system during cold weather poses special challenges. Specific to modified
bitumen materials, these challenges can include maintaining proper sheet material, adhesive, and
asphalt temperatures at the point of application. Cold temperatures may stiffen sheet materials, reduce
the curing or flash-off rate of adhesives, diminish the effective bonding of self-adhesive materials, and
cause mopping asphalts to cool prematurely. By following proper procedures and exercising
recommended precautions, cold weather application can progress more efficiently and effectively,
yielding a high quality result.
Protect Materials Prior to Application
Protecting all roofing materials from the weather is important regardless of conditions, but extra
precaution should be exercised in cold weather. Storage of roofing materials without adequate
protection may affect the quality of the materials, and could also result in moisture being incorporated
into the roof system. Therefore, it is essential to use proper techniques when storing and handling
these roofing materials.
Modified bitumen roll goods, base sheets, and other materials become less flexible at lower
temperatures. When roof systems are installed at ambient temperatures below 50°F (10°C), for best
results it is recommended that all materials should be stored in a dry, heated area for a minimum of 24
hours prior to installation. This allows the modified bitumen to remain flexible during roll out.
All adhesives and primers should be stored in accordance with the manufacturer’s guidelines until just
prior to use. Water-based cements and/or coating materials must be protected to prevent freezing.
Remove moisture, dirt, snow, and ice from roofing asphalts before they are heated; failure to do so can
lead to dangerous frothing inside hot kettles.
Plan Carefully
Acceptable weather conditions are based not only on the actual ambient temperature, but also the total
combination of nature’s elements (e.g. wind, humidity, dew point temperature, sun, cloud cover, shade,
snow, sleet, etc.). Careful planning of work during cold weather can greatly improve the quality of the
installation. Laying out the roof area and placing materials where they will be needed just prior to
application will minimize problems associated with cold weather application.
Surface Preparation
As with any climatic condition, all surfaces to which any roofing materials will be applied must be dry,
smooth, and free of dirt and loose material.
Application Recommendations
For all cold weather applications, follow the manufacturer’s installation instructions as they pertain to
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cold weather application and temperature limitations. Never throw or drop rolls of material. Should
wrinkling of roll goods occur during installation, unroll and cut the material, typically in lengths of halves
or thirds, and allow the cut pieces to relax before application. The time needed to relax may vary
depending on the ambient conditions, product type, and/or material thickness.
Use the Right Materials
If different grades of materials are available for cold weather application, refer to the manufacturer’s
written instructions for guidance on proper product selection.
Complete Each Roof Section Daily as Specified
As the work progresses day-to-day, it is essential that each section of the roof be completed as
specified. Application should be scheduled as specified so that there are no partially completed sections
of the roof left exposed overnight. Additionally, “water cutoffs” should be provided at exposed edges at
the close of each day. Water cutoffs should be removed prior to resuming construction of the roof
assembly.
Torch Application
During membrane application, follow the manufacturer’s recommended torching practice, and industry
torch application safety guidelines (e.g., Certified Roofing Torch Applicator – CERTA). Proper heating
technique is required for proper adhesion of the membrane. The end and side lap areas should be given
special attention, as these are the primary waterproofing junctures of the membrane.
Cold Adhesives
Cold adhesives may be utilized when installing modified bitumen systems in cold weather. Such
adhesives can be utilized for all layers of modified bitumen roof membrane construction. They may
contain asphalt modifiers and can be applied by squeegee, roller, brush, or spray equipment. All
adhesives should be stored at a minimum temperature of 50°F (10°C), and for better results not less
than 70°F (21°C). Follow the manufacturer’s instructions for storage, use, and application. Cold
adhesives become more viscous at lower temperatures, which may affect the application rates. If the
coverage rate exceeds the manufacturer’s installation instructions, reevaluate one of the following: the
application method, the storage of the product, or the condition of the product.
Self-Adhesive Products
At the time of installation, the air, product, and substrate temperatures should be at or above the
minimum application temperature specified by the manufacturer. While the typical minimum
temperature range for application is 40-50°F (4-10°C), consult the specific manufacturer for
recommendations for material storage and handling during colder weather application. Some
manufacturers offer different grades of self-adhesive products, or unique primers, based on their
minimum application temperature requirements.
Hot Asphalt Applied Products
At the point of contact with the modified bitumen sheet material, the mopping asphalt should be
applied at its equiviscous temperature (“EVT”) or a minimum of 400°F (204°C), whichever is higher, or
per manufacturer’s recommendations. A sufficiently high asphalt temperature is essential for adequate
adhesion of SBS modified membranes. It is important for the applicator to be aware that liquid asphalt
cools quickly once applied to a roofing substrate. Components of the roofing system must be installed
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swiftly and “close to the mop.” Be sure that all components are well embedded. Mop-leads (typically no
more than five feet in front of the roll) should not exceed the manufacturer’s instructions. Failure to use
proper application techniques has the potential to result in poor membrane adhesion and possible
system failure.
Proper insulation of all asphalt handling equipment is required to keep asphalt hot in cold weather.
Equipment insulation is also essential for fuel conservation and reducing make-ready time. Use of
insulated tank trucks and rooftop equipment for transporting asphalt, such as hot luggers and mop
buckets, is recommended. Asphalt lines from the kettle to the roof should also be insulated, particularly
when asphalt is being piped over long distances.