A built-up roofing system consists of layers or plies of salt-saturated organic felt, adhered with hot asphalt or adhesive. It is one of the oldest and most durable systems available, and though it can be left bare, it is typically covered with a thick coat of water-proofing material and then with gravel. These coverings provide the additional benefit of reducing cooling and heating costs, and the effects of UV radiation. Built-up roofs are especially resistant to damage from extreme weather conditions, and are easy to repair.
Utilizing a built-up roofing system in temperatures below 45 degrees requires special measures to ensure proper performance. It is strongly recommended that the following guidelines are followed when applying such systems in cold weather:
Plan With Caution
Acceptable weather conditions are not only based on the ambient temperature, but on a combination of weather elements, like wind, humidity and snow. Thoughtful planning of work in low temperatures can greatly improve the quality of the installation. Organizing the roof area and putting materials where they will be needed before application will minimize problems associated with application in cold weather.
Use the Proper Materials
Certain grades of materials are specified for summer or winter use. The grade specified for low temperatures, like winter-grade plastic cements, should be used.
Prep Materials for Use
Base sheets, plies and cap sheets are not as flexible in cold weather. Rolls should be stored on end in a warm and dry location prior to application. Unroll, cut materials, and allow them to relax in warmer temperatures before application. Ignoring proper preparation and handling may lead damage of materials and poor system performance.
Don’t Leave Sections Partially Completed
Unless otherwise indicated by manufacturer’s recommendations, schedule applications so that no sections of the roof are only partially completed and left exposed. As the work progresses, it is essential that each section of the roof be completed on a day-to-day basis as specified. Partially completing, or “Phasing in” a section of the roof is not recommended, as that section will be prone to water entrapment.
Products Applied with Hot Bitumen
Where and when the roofing plies are applied, the mopping asphalt should be at its equiviscous temperature (EVT). Failure to keep the asphalt at the required temperature may result in poor adhesion. Elements of the roofing system must be installed quickly into the asphalt mopping to avoid fishmouthing and other forms of poor embedment. Mopping asphalt should not precede the roofing plies by more than five feet to keep the asphalt from cooling prematurely. Keeping the asphalt within its specified EVT rating range is imperative to compensate for the rapid cooling of mopping asphalt in cold weather. Proper insulation of all asphalt handling equipment is necessary to keep asphalt at a proper application temperature in cold weather. Insulation of the equipment is also vital for fuel conservation and reducing prep time. Asphalt lines from the kettle to the roof should be insulated as well.
Sara is an inbound marketing specialist at Webfor, representing Pacific West Roofing in Portland, Oregon