Ice dams are one of the most common winter roof problems we see across London and Middlesex County. They are also one of the most preventable, once you understand why they actually form.
An ice dam is a ridge of ice that builds up at the edge of a roof, usually right above the eaves. It forms when snow on the upper, warmer part of the roof melts, runs down, and refreezes the moment it reaches the colder overhang. Over a cold snap that cycle repeats, and the ice ridge grows thicker. Once it is tall enough, meltwater backs up behind it, works its way under the shingles, and finds its way into the attic, the ceiling, or the wall below.
Southwestern Ontario's winters are built for ice dams. Lake-effect snow gives us heavy, wet accumulation, and long stretches of freeze-thaw mean roofs are constantly cycling above and below zero. But the snow and cold are not actually the root cause. The root cause is heat escaping from inside the building into the attic, warming the roof deck unevenly. A roof over a properly insulated, properly ventilated attic stays close to outdoor temperature all the way across, so there is no warm zone to start the melt in the first place.
This is the part most homeowners get backward. Raking snow off the roof or chipping at an ice dam treats the symptom for one storm. The actual fix is stopping heat loss into the attic and giving any heat that does get through somewhere to escape:
Watch for icicles hanging heavy along the eaves, a visible ridge of ice at the roof edge, water stains on an interior ceiling near an exterior wall, or a musty smell in the attic after a thaw. See our common roof problems page for more warning signs worth catching early.
In the short term, a roof rake used from the ground to clear the lowest few feet of snow reduces the meltwater feeding the dam. Avoid chipping at the ice itself, since that risks damaging the shingles underneath. For the actual fix, an attic ventilation assessment is the right next step. We install and repair box vents, solar-powered attic fans, and ridge and intake venting on London homes specifically to solve this.
If your home has had ice dams before, the cause is almost always still there waiting for the next cold snap. We will look at your attic's insulation and ventilation, tell you honestly what is driving the problem, and fix the actual cause, not just the ice. Serving London, Strathroy, St. Thomas, Woodstock, and Middlesex County.