How to Prevent Snow From Sliding From a Metal Roof

Measure your roof and diagram its dimensions, including the angle of pitch(es). The size of the roof, its degree of slope or slopes, and customary annual snowfall must all be considered in choosing a snow-restraint system. Local professionals and suppliers are a good source of local experience. Online sources provide formulae for calculating general stress factors.

Choose between a rail-type restraint system and a flag system, which interrupts and retards large falls of snow and ice. Rails can be mounted in groups of two or three rails as well as singly and function like fencing. Flags are scattered across a roof surface in rows and function like rocks interrupting the flow of a stream. Using one system on one area of the roof does not interfere with using the other on a different part of the roof, but otherwise systems are seldom, if ever, combined.

Select the appropriate method for attaching the restraint system to the roof. Adhesives permit attachment to flat roofs or those with ribs, without violating the integrity of the roof surface. The down side to adhesives is that they cannot be used in wet or cold weather and they need time to cure before a reliable seal is formed.

Install the restraint system with screws and washers if snowfall is likely to be heavy and/or icy. This system can be used on flat roofs if care is taken to use neoprene or other recommended washers that will prevent water seepage and rust at installation sites. The danger is leakage. The advantage to the screw system is that it can be installed or modified even in bad weather.

Explore bracketed systems that attach to the ribs of a metal roof. Screwed through the ribs, brackets support rails or flags without penetrating the roof surface. Local experience may help you decide on the suitability of these relatively new restraint-system holders.