Snow rails (or snow guards) come in both metal and plastic formats, but it is generally considered that for metal roofing set ups, plastic snow rails are best. The plastic snow guard came about in 1976, when it was discovered that metal guards were causing some damage to metal roofing and the situation was reconsidered. In addition to getting brittle and breaking in the cold, some of the metal guards were causing severe metal reactions that ended up eroding the metal panel finish. In these cases the conductive liquid or electrolyte was rainwater. During evaporation water becomes concentrated and water films become more conductive, causing the initially benign water to create a dynamic galvanic effect, which causes rust.
This phenomenon generally happens when water gets trapped in a crevice, such as under a screw or between the base of a metal guard and the metal roof. Even water lying against the face of the metal guard and the metal roof for an extended period time can begin the deterioration process. Painting the metal snow rails did not prove to be a reliable solution but it did slow the galvanic reaction process down somewhat. We did find however that with the painted metal snow guards, the corrosion would usually begin to form around friction points and in time would continue to eat its way through the guard and panel.
In normal circumstances, the reliability of the metal snow rails was entirely dependent on the location of the home on which they were placed. This is because geographical location plays a large part in the rate at which corrosion occurs, meaning that areas with lots of salt water and pollution are the worst off. Homes on the coast with all the sea air generally had the most rapid rates of failure.
Due to the many issues caused by metal roofing used with metal snow rails, the plastic ones became very popular on that sort of roof, as they avoid the same pitfalls. Plastic ones did not react with the metal roof and cause the accessory to get eaten away or the roof to rust. The plastic guards also held up better in extreme temperatures, unlike cheaper metal castings that would become brittle and crumble.
Though metal guards were useful on asphalt or tile roofing but not metal, they were still popular because of the facility to change their color to match the color of the roofing. Some plastic guards give you this option, but many people that choose plastic guards go for the clear ones, as these don’t show up very much. It really depends on personal preference and what you think looks best on the roof of your home.
If you want to know more about snow rails and what kind is best for your home, then look online or ask a local roofing expert.
Want to find out more about snow rails, then visit Esme Spence’s site on how to choose the best snow rails for your needs.