What Edmonton’s Freeze-Thaw Cycles Actually Do to Your Roof

After a snowfall, a roof may seem fine from the outside but actually have damage inside. Water becomes free-flowing in cooler months after snow melts, and the water is forced back through the weak points of the roof system in the following cold months.

These temperature fluctuations don’t necessarily harm a good roof. Aging shingles, loose flashing, clogged drainage, and heat loss through the attic are more likely to cause problems. An inspector’s timely visit to the roof can locate these weaknesses before they become a leak through the next melt-refreeze cycle. Here is What Edmonton’s Freeze-Thaw Cycles Actually Do to Your Roof!

Edmonton’s Freeze-Thaw Cycles and How They Impact Your Roof 

They Turn Small Gaps Into Water Entry Points

Meltwater can enter openings through cracked shingles, uncovered fasteners, the valley, the vent, the chimney, and the flashing. Water that freezes within a weak connection in the joint or within saturated material imposes extra stress on that part.

Water and the resulting freezing and thawing may help cause early deterioration of building materials. Long-term causes of degradation in the building identified by the City of Edmonton include 

• freeze-thaw cycles
• frost penetration
• repeated wetting and drying. 

Imagine a hypothetical roof where there is a small gap next to a vent flashing. A few drops may fall on one warm afternoon. However, following a few melt and freeze cycles, the movement around the gap could lead to sufficient moisture to discolor the roof deck or attic insulation. 

They Create Ice Dams

Ice damming occurs when warm air from the interior of the house causes the snow cover on the roof to melt, and snow layers accumulate on roofs and trickle down to the lower levels. Water flows towards the colder areas at the eaves, freezes, and slowly creates a flow of ice at the roof crest. That water will allow additional water to gather behind it and under roofing materials.

The City of Edmonton refers to ice dams as one of the most prevalent roof issues in Canada. These can damage gutters and downspouts, block drainage, and cause interior damage.

An ice dam can be accompanied by large icicles, but not all big icicles signify an ice dam. Keep an eye out for excessive ice accumulation along the perimeter of their roof, water stains around their exterior walls, and damp insulation in the attic. 

They Stress Shingles, Flashing, and Sealants

During hot periods, roof materials are subjected to expansion, and during cold periods to contraction. Huge temperature differentials can cause exterior materials such as roofing to buckle, bow, crack, and break over time.

Flashings around valleys, walls, chimneys, and similar areas are particularly significant in that they will divert rain and snowmelt away from joints. For an effective snow melt system that accommodates the movement between adjacent materials, Canadian building advice says that a proper flashing design can help keep snow melt out of the roof deck. 

They Can Block Roof Drainage

Water may clog gutters, downspouts, scuppers, or roof drains if it is refrozen. On steeply sloped roofs, this disproportionately stresses the edge of the roof. Trapped snowmelt can pool in low spots on a flat or low-slope roof where it adds weight to the roof system. 

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How to Reduce Freeze-Thaw Roof Damage

Before and during winter:

• Ensure good ducting and drainage.
• Inspect roofs for damage to shingles, valleys, vents, and flashing.
• Repair air leaks in the attic and poor insulation.
• Check for ceiling stains; do not paint over these stains.
• Schedule a checkup if you’re having frequent leaks or large ice formations.
• Do not pull ice from the roofs, as it can break shingles and become a fall hazard. 

The aim is not to maintain a warm roof. This is to prevent hot and cold spots, moisture control, and drainage of the meltwater once it gets on the roof. 

Final Thoughts

What Edmonton’s freeze-thaw cycles actually do to your roof depends on the state of the roof before the cycle. A strong roof with proper insulation and drainage systems is better equipped to handle flashings that melt and refreeze over time, improving without breaking, aggravating already poor roof openings, eliminating trouble from drainage issues, and preventing ice dams.

Monitor and repair any roofing standing seam problems or attic flatness during the winter months, and before cosmetic issues become a bigger project.

Read more: Top 7 Roofing Mistakes That Cost Homeowners Thousands