Blog PostMarch 18, 2021 - Educational
Surviving the Cold – Winter Construction: Flat Roofing
Despite below freezing temperatures, winter construction is possible and can be high quality when the correct precautions are taken. While there are inevitable schedule delays due to high winds, snow and extreme cold temperatures, winter roof construction is feasible. We’ve outlined the risks associated with this type of work, as well as the appropriate precautionary measures that must be taken to ensure a quality repair.
Flat roof repair or replacement is commonly completed in the winter and may be less expensive during the colder months, as contractors are hungry for work. Hot Applied Built-Up Roofing (BUR), Modified Bituminous (Mod Bit), as well as single ply membrane systems can be installed in cold weather and will provide a similar service life to membrane installed in warmer weather. BUR and Mod Bit systems application involve heating asphalt to bond the layers of reinforcing felts and seal joints, while TPO and PVC systems are heat-welded at seams. To successfully install a flat roof membrane during cold weather, consider the following:
1. Consult the manufacturer and your Consultant to determine suitable products and preparation for the expected temperatures. Generally, flat roof membranes should not be installed when temperatures are below -18°C or during inclement weather. Adhesives and sealants should typically be stored above 5°C.
2. Single ply membrane systems can be secured to a roof deck using mechanical fasteners or adhesives or they can be weighted down with ballast, often stone ballast. Installation of fully adhered systems should be avoided during cold weather as there is a risk the adhesive may prematurely set before proper adhesion takes place. This may result in blisters and wrinkles, increasing the probability of punctures. Single-ply adhesives can be delicate and complex - remember to consult your engineer for your specific project and materials!
3. Hot asphalt used for BUR or Mod-Bit must be installed at specified temperatures to ensure proper viscosity and adhesion. The hot asphalt temperature will decrease faster in colder weather therefore precautions must be taken. These precautions include using insulated piping and buckets and shortening the time membrane is installed following mop or mechanical spreader application. If the asphalt cools before the felt or membrane is laid, the edges and laps may not be fully sealed, and wrinkles or blisters may develop.
We often hear that there are two seasons in Canada: winter and construction seasons. We now know that the construction season for roofing can be extended year-round provided there are proper precautions taken. Proper quality control and third-party review is critical to protecting your investment on any construction project, and even more so if you are considering winter construction. By keeping a close eye on the forecast and taking proper precautions, winter construction can produce high quality, long lasting repairs.
Check back next winter for Surviving the Cold – Winter Construction: Concrete!