Almost ice dam time again
Although there are many areas in the South, Southeast, and Southwest that don’t have the problem, the rest of us have to worry about ice dams on our roofs. Most steep slope roofing products require a special installation technique on the eaves of the roof to prevent the consequences of ice damming.
As you may know leaks from ice damming are caused by snow on your roof melting from heat loss from the attic. The melted snow goes down the roof and re-freezes at the eave where there is no heat loss (no attic). As more snow melts the water runs down and ponds at the re-freeze point or “ice dam”. Steep slope roofing like DaVinci composite shake are not “waterproof”, they shed water. Therefore, if water ponds at the bottom of the roof and backs up the roof leaks. That is the reason for a peel and stick membrane on the bottom of the roof; it makes the areas where ice damming is possible, water-proof.
There are other factors involved with ice dam issues. One of those can be inadequate insulation or ventilation in your attic. In theory, with proper insulation and ventilation, the temperature in your attic can be very close to the outside temperature. If this were the case you wouldn’t have ice damming problems because all the snow on your roof would melt at the same rate.
DaVinci lightweight roofing materials require an ice barrier consisting of a self adhering polymer modified bitumen sheet be applied to a point at least 24″ inside the exterior wall line of the building in areas where the average daily temperature in January is 25 degrees F or anyplace where ice buildup is probable.