Snow Load & Ice Dams: Why Metal Roofs Win Every Ontario Winter
Ice dams destroy Ontario homes every winter — forcing water under asphalt shingles and into wall cavities. Standing seam metal roofing eliminates ice damming permanently.
If you own a home in Southern Ontario and have an asphalt roof, you've likely dealt with ice dams — the thick ridges of ice that form at the eave edge and force melt water back up under shingles and into wall cavities. Ice dams cause catastrophic water damage, rot, and mold, and they return every winter as long as you have an asphalt roof. Standing seam metal roofing eliminates ice damming permanently.
What Causes Ice Dams?
Ice dams form when heat escaping through the roof deck warms the upper roof surface, melting snow. The melt water runs down the slope and refreezes when it reaches the cold eave overhang — where there is no heat below. This builds up the ice dam. As more melt water backs up behind the dam, it finds the path of least resistance: under the shingle laps and through the roof deck into the wall and ceiling cavities below.
Why Asphalt Shingles Are Vulnerable
Asphalt shingles are designed to shed water running down their surface — not water backing up beneath them. When the ice dam forces water uphill, the standard asphalt lap is no match for sustained hydrostatic pressure. Ice and water shield underlayment provides some protection, but it has limits. And once water enters the roof assembly, the damage begins: rotting decking, saturated insulation, mold in wall cavities, and damaged ceilings.
How Standing Seam Metal Eliminates Ice Dams
Standing seam metal roofing addresses ice damming from two directions simultaneously. First, the smooth metal surface sheds snow naturally — reducing the snow mass available to melt and refreeze. Second, the concealed fastener, continuous panel construction leaves no laps or seam penetrations where backed-up water can infiltrate. There is simply no mechanism for ice dam water to enter the roof assembly.
Important: Standing seam metal roofing should be installed with proper thermal break underlayment to minimize heat loss through the roof deck — which reduces the temperature differential that causes ice damming in the first place. VAH Construction includes appropriate thermal break underlayment in every installation.
Snow Load on Metal Roofs
Ontario's building codes specify minimum snow load requirements for roofing systems. Standing seam metal easily exceeds all Ontario minimum requirements. More importantly, metal's smooth surface naturally reduces the snow load that builds up — snow slides before it reaches dangerous accumulation levels on a properly pitched metal roof. This reduces structural stress on the building and eliminates the safety hazard of avalanching snow accumulations.
Frequently Asked Questions
If I install a metal roof, will I still get ice dams?
Ice dam formation is effectively eliminated with properly installed standing seam metal roofing. The combination of a smooth, non-retentive surface and the continuous sealed panel system means there is no mechanism for ice dam-related water infiltration.
Does metal roofing increase the risk of dangerous roof avalanches?
On steeply pitched roofs, large snow accumulations can slide off quickly. VAH Construction can install snow guards or snow retention bars to control snow release in areas where sliding snow would be hazardous (over entries, walkways, or driveways).
My asphalt roof has chronic ice dam problems. Can I switch to metal?
Absolutely — and standing seam metal is the definitive solution. VAH Construction will assess your roof structure, ventilation, and insulation as part of the installation process to ensure the new metal roof performs optimally and ice damming is permanently resolved.
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