What Is Ice Damming?

Ice damming occurs when heat escapes through your attic and warms the roof deck, melting snow above. That meltwater flows down the roof slope and refreezes at the cold eaves — forming a dam of ice. As more meltwater backs up behind the dam, it can seep under shingles, into the roof deck, and eventually into your walls and ceilings. The water damage that results is often extensive and expensive.

The Role of Soffit Ventilation

Proper attic ventilation is the primary defence against ice damming. The system works by allowing cold outside air to enter the attic through vented soffits at the eaves, flow across the underside of the roof deck, and exit through ridge vents at the peak. This keeps the entire roof surface at a consistent cold temperature — preventing the differential heating that causes ice dams.

When soffits are solid (unvented) or when ventilation is blocked by insulation, this airflow stops. The attic heats unevenly, and ice dams become almost inevitable in Edmonton winters.

Signs Your Soffits May Be Inadequate

  • Ice forming at your eaves or gutters after snowfall
  • Icicles along the roofline (attractive, but a warning sign)
  • Water stains on ceilings near exterior walls in late winter
  • Frost buildup on the underside of the roof deck (visible in attic)
  • Solid aluminum or wood soffits with no ventilation strips

Calculating Proper Ventilation

The Canadian building code recommends a minimum of 1:300 ratio of net free ventilation area to attic floor area. In practice, for an Edmonton home in our climate, we typically recommend exceeding this — 1:150 is preferable. A qualified contractor can calculate the correct ventilation for your specific attic configuration.

Vented vs. Solid Soffit Panels

Modern aluminum soffit panels come in fully vented, partially vented, and solid configurations. A properly designed soffit installation combines vented panels in most areas with solid panels at specific locations (like at valleys). The vented area must be calculated correctly — simply installing vented panels throughout isn’t always the right approach.

What We Do Differently

When we install or replace soffits, we always assess the existing attic ventilation situation and check for blocked baffles. We won’t simply replace like-for-like if the existing system is inadequate. A proper soffit installation is a meaningful investment in your roof’s longevity.

Contact us for a free soffit and ventilation assessment.