How does ice damage my shingles?
You may have noticed that occasionally canvassers will reach out to homeowners after a particularly cold spell offering roof inspections to catch ice damage. While cold on its own is not generally damaging to a roof, when you add in moisture, things can get tricky. This is because of an unusual property of water, which we will go over here.
For most materials, the hotter they get, the more their molecules vibrate. Usually, although this movement is very small on a particle level, when factored out for each particle, the result is that the material takes up more space the hotter it gets. Conversely, when materials get colder, that particle movement is reduced, making the material smaller.
For water, although the aforementioned process does still play out, the freezing process (turning from a liquid to a solid state) actually results in more mass. This is due to the structure of water molecules and their propensity to form hydrogen bonds. The formation of these bonds creates an empty space between the molecules. In a liquid state, these bonds are constantly reforming, actually resulting in less empty space. But, when water freezes, the molecules settle into the stable configurations formed by the hydrogen bonds, and that empty space is maximized, making the material (ice) expand.