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
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
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. Read more

The maximum slope considered by ARMA to be suitable for normal asphalt shingle application is 21:12, or 21” per foot. The use
of asphalt shingles on slopes greater than 21:12 (e.g., mansard roofs) requires the use of special application methods because
very steep slopes reduce the effectiveness of factory-applied self-sealing adhesives, especially in colder climates and shaded
areas. If normal application methods are used for asphalt shingles on very steep slopes, problems can occur that are not a result
of any weakness or defect in the product, but rather because special application methods for very steep slopes were not
If a roof slope exceeds 21:12, the shingles should be applied by the following recommended method:
 Secure the shingle to the roof deck with fasteners as directed by the roofing manufacturer. Manufacturer directions may
call for more than the normal number of fasteners per shingle and may provide specific fastener locations.
 Apply a manufacturer-recommended asphalt roof cement complying with ASTM D4586, Standard Specification for Asphalt
Roof Cement, Asbestos-Free, or other cements approved by the roofing manufacturer under all shingle tabs in spots
equivalent to the size of a quarter (about 1” diameter), immediately upon installation.
o For standard laminated shingles (i.e., ‘no cut-out’ shingles) apply four spots of cement under each shingle near the
lowermost edge, with two near the corners and two equally spaced between the corners.
o For ‘three-tab’ shingles, apply two spots of cement under each tab near the lowermost corners.
o For other specialty shingles, refer to manufacturer’s recommendations.
 Over-application of adhesives is not recommended; follow manufacturer’s recommendation for cement type and minimum
and maximum quantities.
 An unvented space may be behind a mansard roof. It is important to provide a properly ventilated flow-through air space
behind the roof sheathing to prevent the entrapment of moisture-laden air. Additional information is available on ARMA’s

For many years, roof discoloration caused by algae has been observed throughout the United States and Canada. The
discoloration usually has a brown to black appearance, and may be mistaken for fungus growth, soot, dirt, moss, or tree
Gloeocapsa magma is probably the most prevalent of several algae species that contribute to discoloration. All species are
transported through the air, and tend to collect and grow upon roofing structures. Natural pigments produced by these algae
may cause a white or light colored roof to gradually turn dark brown or black. Discoloration may appear as uniform
discolorations or streaks. The algae discolorations should not be confused with moss or tree droppings, which typically
produce only localized discolorations.
This type of roof discoloration has been most widespread in the Gulf States and along the Northwest and Eastern Seaboards.
It is not, however, confined exclusively to these regions. Algae growth occurs to varying degrees in all regions of the country,
especially those subjected to warm, humid conditions. It should be noted that almost all types of roofing systems are
susceptible to algae discoloration. It is, of course, most readily visible upon light colored roofs, while it is not so visible upon
darker shades of roofing.
Algae discolorations are difficult to remove from roofing surfaces, but may be lightened by applying a solution of liquid
household chlorine bleach (sodium hypochlorite) and water. Directions for mixing solutions of these ingredients may vary
among shingle manufacturers and depend on the amount of discoloration. A typical solution should be one part chlorine
bleach and one part water. Other cleaning chemicals or methods should not be used without approval of the shingle
First, gently disperse this solution on the roofing surface. Use normal precautions for handling bleach including eye protection
and rubber gloves. Be sure to apply it carefully to avoid damage to other parts of the building and the surrounding landscape.
Avoid scrubbing the surface, as this friction may loosen and remove granules. If possible, always work from a ladder and/or
walkboards to avoid direct contact with the roof surface. Observe all possible safety precautions when working on or near the
roof. The solution should be left on the roof for at least 15 minutes but for no more than 20 minutes. Finally, rinse the solution
from the roof by gently spraying the surface with water. Be warned that this solution application and rinse process will make
the roof surface slippery and potentially hazardous to walk on during treatment.
The effectiveness of a cleaning technique is only temporary, and discoloration will likely reoccur. However, several types of
algae resistant roofing products have been developed and are now commercially available. These asphalt roofing products
are specifically designed to inhibit algae growth for extended periods of time.
High pressure washing systems are likely to damage asphalt roofing and should not be used on asphalt roofing for removing
algae or for any other purpose.