Your roofing system is made up of more than just shingles. An efficient roofing system consists of properly installed shingles, ventilation (roof vents), air intake (soffit vents), attic insulation, water barriers and drainage system (eavestroughs). Missing even one of these elements can lead to any number of problems including roof leaks and ice damming. Having improper ventilation, air intake and attic insulation also causes your home’s shingles to age much quicker. On hot summer days, warm air gets trapped in the attic underneath your home’s shingles, which causes them to curl.
A properly installed, properly vented roofing system will allow you to get the most out of your roof before it has to be repaired or replaced.
Contractor Mike Holmes has written an excellent on his website discussing the causes and harms of ice damming.
In short, an ice dam is when a ridge of ice forms at the edge of your roof and prevents water and melting snow from properly draining through your eavestroughs. Often, this happens because the roof does not have proper ventilation. The warm air trapped in the home’s attic causes the snow to melt and refreeze as ice. The ridge of ice acts as a blockade or dam, not allowing water from the melting snow to properly drain.
Improper drainage that ice damming causes adds extra stress to your roofing system, which can lead to leaks and shorten the lifetime of your roof.
The best way to prevent ice damming is to ensure that you have a properly installed roofing system, including proper attic insulation and ventilation.