Wisconsin winters present some problems with slate & tile roofs. Because slate and tile are a hard and usually smooth surface they are more prone to major ice slides than standard shingle roofs. When snow accumulates on the roof it starts to bond together when heat loss from inside the house melts the bottom layer of snow during the warm hours of the day and then re-freezes in the cooler nighttime hours.
Several cycles of this can create a huge and heavy ice mass which may not be visible because it is forming on the bottom layers. Under the right conditions the ice mass is heavy enough that it lets loose, slides down the roof, and free falls onto whatever is underneath. There are two types of snow guards that can prevent this. One type is individual snow guards fabricated from copper and bronze that are fitted in with the slates or tiles in a certain density appropriate for the roof area.
The ice forms around the snow guards which are secured to the roof and therefore will not slide. The other type is a rail type which is fitted along the lower edge of the roof with 3 brass pipes mounted in bronze brackets. The pipes stack vertically in the brackets and create a barrier to hold the ice formations above. Snow guards are typically placed over driveways and walks. Large ice formations along with icicles form when there is accumulated snow on the roofs and the temperatures are in the mid to high 20s.
The roof area over the inside walls is warmer at the eaves due to heat loss from the interior areas. The snow melts on the under side of the snow pack and runs down the roof as water and re-freezes when it reaches the cold section of roof at the eave. Several daily cycles of this create the ice formations. When the snow continues to melt and the ice is large enough the water will start to stand behind the ice and work it’s way into the nail holes that fasten the roofing.
This will continue until the snow is melted from above. Roof and gutter heating cables are laid in a pattern that loop onto the roof covering the cold area and extend into the gutter and down the downspout. When turned on they create a path through the ice that allows the melt from over the warmer section of the roof to pass through the cold section be relieved by the heated gutter and downspout.
Why shovel your roof and chop ice formations 20’ off the ground in the middle of winter? Just flip a switch and watch the cables melt your worries away!