Ice dams are thick ridges of ice that form along the lower edge of a roof, usually near the eaves. They develop when snow melts higher up on the roof, flows downward and then freezes again once it reaches a colder section near the roof’s edge.
They’re common during Ontario winters and can become more than an annoying row of icicles. When an ice dam prevents melting snow from draining properly, water can collect behind it and potentially work its way beneath the roofing system.
Understanding why ice dams form can help homeowners identify the underlying problem and reduce the risk of roof damage.
What Is an Ice Dam?
An ice dam is a buildup of ice that prevents melting snow and water from draining off a roof normally.
The process usually begins when heat escaping from the home warms part of the roof above freezing. Snow sitting on that warmer surface begins to melt and runs toward the eaves.
Because the eaves extend beyond the heated portion of the house, they can remain significantly colder. Once the water reaches this area, it can freeze again.
This cycle can happen repeatedly. More snow melts, more water reaches the roof edge and another layer freezes. Eventually, a substantial ridge of ice can form.
What Causes Ice Dams?
Ice dams are generally caused by uneven roof temperatures rather than simply having snow on your roof.
Heat from inside the house can escape into the attic and warm the underside of the roof deck. Areas of the roof above the heated living space may become warm enough to melt snow while the overhanging eaves remain below freezing.
Several conditions can contribute to this temperature difference, including inadequate attic insulation, air leakage from the living space into the attic and poor attic ventilation.
Weather also plays an important role. Long periods of snow cover combined with temperatures that fluctuate around freezing can create favourable conditions for repeated melting and refreezing.
Can Ice Dams Damage Your Roof?
Yes. The biggest concern isn’t necessarily the ice itself, it’s the water that can accumulate behind it.
Shingles are designed to shed water as it moves downward across the roof. When an ice dam blocks that path, water can remain on the roof or move in directions the roofing system wasn’t designed to handle.
Water may eventually work beneath shingles and reach the underlayment or roof decking. If the roofing system doesn’t adequately prevent that moisture from travelling farther, a roof leak can develop.
Repeated moisture exposure can also contribute to deterioration of the roof deck and other materials.
What Does Ice Dam Damage Look Like?
Ice dam problems aren’t always obvious from outside the house. A large ridge of ice along the eaves can be a warning sign, but homeowners should also watch for problems inside.
Water stains on ceilings or exterior walls, damp insulation, peeling paint, moisture around windows and unexplained winter roof leaks can potentially be associated with ice damming.
Outside, you may notice large amounts of ice accumulating along the roof edge or behind gutters.
Icicles alone, however, don’t necessarily mean that your roof has an ice dam. They’re better treated as a reason to pay attention to how snow and water are behaving on the roof.
How Does Ice & Water Shield Help?
Ice and water shield is a self-adhering waterproof membrane installed underneath the finished roofing material in vulnerable areas.
Unlike shingles, which primarily shed water, the membrane provides an additional waterproof barrier if water gets underneath the shingles.
This is particularly important near the eaves, where ice damming can cause water to back up.
Ice and water protection doesn’t prevent an ice dam from forming. Instead, it’s part of the roofing system designed to help protect the structure if water backs up beneath the shingles.
Can Gutters Cause Ice Dams?
Gutters aren’t usually the underlying cause of an ice dam, but drainage problems can make winter conditions around the roof edge worse.
Leaves, debris and frozen water can prevent gutters and downspouts from draining properly. Keeping the drainage system clear helps melting snow leave the roof and move away from the house.
However, repeatedly experiencing substantial ice dams can indicate a larger issue involving heat loss, insulation, air sealing or attic ventilation rather than simply a gutter problem.
How Can You Prevent Ice Dams?
Long-term prevention generally means addressing the conditions causing sections of the roof to become warmer than others.
That can include improving attic insulation, sealing areas where warm household air enters the attic, maintaining appropriate attic ventilation and ensuring the roofing and drainage systems are functioning correctly.
Removing excessive snow from vulnerable roof areas may sometimes reduce the amount of water available to form an ice dam, but homeowners should avoid climbing onto an icy or snow-covered roof. Roof work in winter can be particularly dangerous.
If ice dams repeatedly form in the same areas, it’s worth determining why they’re forming instead of simply removing the ice each winter.
Should You Remove an Ice Dam Yourself?
Avoid chopping, hammering or using sharp tools to break ice away from your roof. Doing so can damage shingles, gutters, flashing and other roofing components.
You should also be cautious about using chemicals or salts that aren’t intended for roofing materials.
If a large ice dam has formed or you’re already experiencing water intrusion, having the situation assessed professionally is generally safer than climbing onto the roof yourself.
Does an Ice Dam Mean You Need a New Roof?
Not necessarily.
An ice dam can occur on a roof that is otherwise in good condition. Whether repairs are required depends on whether water has penetrated the roofing system and whether any materials were damaged.
A localized problem may only require repairs. More extensive work could be necessary if moisture has damaged the roof decking or if the existing roofing system is already deteriorated.
The important part is determining where the water travelled and what, if anything, was damaged.
Roof Damage From Ice Dams?
Ice dams can force water beneath your shingles and lead to damaged roofing materials, leaks and moisture problems inside your home. If you think an ice dam has damaged your roof, RoofingGuys.ca can inspect the affected area and determine what needs to be repaired.
Contact RoofingGuys.ca today to request a free roofing estimate.
