LMCURBS®

Division of Longview Mechanical Contractors

1-800-284-1412

The Effects of Snow On The Roof

When snow accumulates on a roof, it can build up to significant depths. When snow is falling, the snow (and ice) adjacent to the roof panel surface will develop cohesion to that surface. Following the snowfall and its accumulation, the blanketed roof will warm as a result of one or two separate phenomena: (a) the snow is translucent and so radiation from the sun passes through the snow, warming the panel beneath; and (b) heat loss from the building passes to the roof surface, warming it. In either case, the blanket of snow insulates the roof from potentially cold ambient temperatures, and therefore either of these roof warming phenomena will occur even if ambient air is well below freezing.

As the roof surface warms, and the bond between the bank of snow and the roof surface thaws, the cohesion is not only lost, but the interface of snow and roof panel is lubricated by melt water. Frictional coefficients of the premium paints (Kynar) which are typically used on high profile roofing are very minimal. When the bond between the snow bank and roof panel is freed, all the gravity loads within the snow bank are experienced within the blanket at the ridge area-opposing banks trying to slide off the roof. When these forces become greater than the shear strength of the snow bank at this area, the bank shears at the ridge and an avalanche occurs. Similarly, snow banks cling to roof protrusions like chimneys, parapet walls and flues. When the cohesion to the protrusion is finally broken, the slide occurs.

Disclaimer: Note that the set screws must be torqued to 115" lbs. with a screw gun and checked periodically during installation. LMCurbs is under no obligation if a failure occurs from an improper design or installation. This information is not meant to fit every application. For severe applications, call 1-800-284-1412 to discuss your particular situation.