Ice damming

As ice builds up, water can actually work its way upwards. Naturally, people tend to think of water as always running downwards, following the direction of gravity, but there are circumstances such as ice damming where when temperatures fluctuate around freezing, more or less a few degrees above or below 32゚F, water can build-up and actually work its way upwards into cracks and crevices behind materials that are concentrically overlapped and into building spaces that water, in a wet state would not normally go.

Ice damming happens because as temperatures hover around the freezing mark, some of the precipitation on buildings will freeze into ice.  That ice, as it lays on and against building facades and building elements will build up.  As the ice builds up and as temperatures fluctuate, hovering around 32 degrees Fahrenheit, some of the ice will melt.  However, between overlayed or concentric building materials, the ice itself may block the flow of water.  As the freeze-thaw process repeats, ice and build further and further upwards and into buildings.

Measures can be taken to build building assemblies in a way which limits and or prevents ice damming.