COLD WEATHER APPLICATION TIPS FOR ROOF COATINGS

Revised/Published January 2025

Bitumen, as well as several other non-bituminous resins used in roof coatings, are often referred to as thermoplastics. This means that they soften as the temperature increases and harden as the temperature decreases. Their viscosity is also dependent upon temperature. When warmed or heated they are more fluid. At lower temperatures, they become more viscous. Some solvent-based or high solids coatings in the market today are formulated for application at temperatures year-round, whereas water-based roof coatings, are usually designed for application temperatures of 50° F (10⁰C) and higher.

To accommodate the wide temperature range associated with certain geographic climates, some manufacturers offer “all temperature” products; while others may offer products formulated for seasonal use. Check with your supplier or manufacturer to determine which version(s) they may offer and to assist with proper product selection. If the manufacturer offers various viscosity grades, be certain to inquire as to how they distinguish one grade from the other, which may involve specific container markings or labels, and to determine the appropriate limitations on their use. Regardless of the weather, there are always important “do’s and don’ts” to follow for a successful coating application. These include:

Storage:

Always keep the product stored as per the recommended storage temperatures listed on the product’s label or technical data sheet. Ideally, a temperature-controlled space is generally the preferred type of storage area. If the coating must be kept outside, store the containers as close together as possible and under a moisture proof tarp. This will slow the internal temperature drop of the product, helping to maintain the viscosity and application properties closer to the desired target for a longer period of time. While this technique can help, it is important to recognize that significant temperature loss can still occur, particularly during the evening hours, which may make supplemental heating necessary prior to application. Further, water-based products that are susceptible to freezing may be damaged if subject to temperatures at or below 32ºF (0⁰ C), rendering them unfit for installation.

Heating:

With proper storage in a temperature-controlled space, additional heating should not be necessary. However, on the job site, the use of heated storage cabinets, heated storage units or warming devices which use circulating oil to heat cold applied roofing materials may be utilized to obtain an acceptable application viscosity. Consult the equipment manufacturer for specific information on the safety and operation requirements pertaining to the heating equipment that is used and the coating manufacturers’ available literature on guidance for storage temperatures.

Surface Preparation:

Never apply roof coatings to a frost, snow- or ice-covered surface. In addition, for most solvent-based roof coatings, the surface must be dry unless the coating has been specifically formulated for adhesion to wet surfaces. Consult the manufacturers’ instructions for specific recommendations and requirements, particularly as it relates to cold weather application.

Cold Weather Application Tips for Roof Coatings

Application:

Follow manufacturer’s instructions for substrate temperature, substrate moisture content, environmental temperature, and environmental humidity requirements before proceeding with application. When applying roof coatings in cold weather, consider the application and curing times of manufacturers coatings and predicted weather forecast. Remember when coating a black roof, the surface will absorb infrared heat from the sun, making the roof temperature warmer than the air temperature, helping to improve the overall cure rate. Covering a large portion of the roof with tarps can allow for a quicker start in the morning. Water will accumulate on the surface of the tarp overnight; so carefully remove the tarp in the morning and the roof surface underneath will be dry and ready for the job to start much faster than waiting for the moisture to evaporate. Special limitations may be specified for particular roof coatings, such as emulsions and asphalt aluminum coatings.

These may include details regarding minimum temperatures allowed, as well as exposure to moisture within a certain time period following the application.

Cure Time:

While modern technology permits the application of some roof coatings at low temperatures, expect the cure time to be longer than on a warm summer day. A product that may cure overnight at a temperature of 70°-75°F (21-24 ⁰ C) may take several days to cure at 40°F (4⁰ C).

Water-based coatings (emulsions) require temperature conditions which permit complete evaporation of the water before the film can be subjected to freezing or moisture (rain, heavy dew, snow and frost). While there are some modified, water-based coatings that have shorter set and cure times, it is important to consider their limitations and to review the application conditions with the manufacturer, prior to use.

Roof Coatings Manufacturers Association
2551 Lake Road Ontario, NY 14519 · www.roofcoatings.org
A member service provided by the Roof Coatings Manufacturers Association

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