Roofers must be aware of cold weather limitations and precautions for all materials that are being installed on a roof. Cold weather could result in unwanted moisture into the roof assembly if the installation is not closely monitored.

• Built-up roofing can be applied in cold weather but precautions with asphalt must be recognized.
  • The asphalt bitumen should be sufficiently hot to bond the roofing materials together and properly penetrate BUR membrane reinforcements. Bitumen may have to be heated to temperatures close to actual flashpoint temperature in order to obtain proper application temperature. However, the bitumen must not be overheated or held at high temperatures for prolonged periods as it will degrade and become unsuited for use in the construction of the roof system.
  • Good felt mopping in the winter time is essential, so that the felts and other materials are thoroughly adhered to each other by the bitumen that has been spread either by machine or hand mopping. Should the bitumen be placed and become cool before the felts or other materials adhere to it, serious roof leaks and damage to the roof may occur.
  • The use of hot bitumen as waterproofing medium or adhesive during cold weather demands much greater care and, in all probability, less speed than in the warmer weather. All felts and other materials must be thoroughly adhered and bonded.
• Type of substrate and surface temperature affects self-adhering membranes.
• Adhesives have varying curing and application limitations. Even within these limitations, drying/curing times may be affected by weather conditions (temperature, humidity, wind velocity, etc.).
• Ensure the uniform securement of adhesion, membrane and components.
• Temporary membranes and/or night seals are required to prevent water from entering the roof assembly at the end of each days roofing operation.