If a resident calls to report a roof leak after one or more snowfalls, it’s possible that an ice dam is the culprit. One of the biggest cold-weather problems is ice damming, which is not a fault in the roof itself but a reaction between snow and ice buildup, and potentially, the insulation conditions below. It’s important for homeowners to know what causes ice damming and how it can be repaired, before you face an emergency situation.

An ice dam is a ridge of solid ice that commonly forms along the eaves of a roof. During a natural freeze and thaw cycle, especially with rapidly changing temperatures, ice dams can easily form. It doesn’t take much more than an inch or so of snow or ice to block natural runoff at the edge of a roof. Once in place, though, it prevents further snow melt from draining into the gutters.

Instead, all that melting ice and snow is dammed up and can seep under the edge of the roofing materials.
However, an ice dam doesn’t mean that there’s a problem with the roof. On perfect shingle roof installations leaks still occur when large ice sheets and ice dams form during the winter. That is because shingle roofs are designed to keep out flowing water, not standing water. Standing water goes underneath shingles and through normal nail holes in felt. When an ice dam is formed, it is an indication that there’s inadequate insulation inside the crawlspace or attic that is letting heat escape. Though excessive heat may seem counterintuitive to forming ice, the escaping heat will warm up most of the roof, where the snow will drain quickly to the colder edges of the roof, and then build up a ridge that prevents further draining.

In addition to leaks, there are several other problems that can occur with this issue. The weight of the ice can damage gutters by warping and bending them downward; the ice can have sharp edges that wear and tear on the gutter materials. When you see a gutter filled with long, thick icicles, it is one sign that ice damming is present and should be addressed – and the icicles should be removed before they fall and hurt someone. Even without gutters, an ice dam can form along the edge of the roofline and produce seepage inside.

Products such as Ice & Water Shield and other similar treatments prevent most ice-related winter leaks; however, leaks can still occur on perfect roof installations. When ice damming conditions exist on roofs that have not leaked during rain, there is rarely a defect as explained above. As a result, it usually doesn’t make sense to send a repairman since the roof itself doesn’t have a fault. Instead, there are two approaches to handle the problem and prevent future issues.

Roofing codes require roofers to install ice & water shield in the areas most likely to trap water under ice. The ice damming membrane can keep water out for approximately 48 hours. During that time the water usually refreezes or drains when it is warm. Ice damming membrane eliminates nearly 100 percent of leaks under average winter conditions. It fails when water sits too long under ice. Also, water gets beyond the membrane when the ice sheets extend beyond the area it is installed.

Unfortunately, there are no good construction solutions for this problem on shingle roofs. The only solution is to melt or remove the ice which would need to be redone each time extreme ice conditions occur.