Ice Damming

The following are potential causes of ice damming. Ice dams are a build-up of ice, generally at the roof edge, which allows melted snow or water to back-up under the roof coverings, causing leakage. Ironically, ice damming is generally not caused by faulty roofing; it is a product of poor attic ventilation.

Evidence of previous ice damming.

    • Roof covering/shingle damage caused by ice/snow removal.
    • Excessive wear of roof coverings/shingles at the roof edge.
    • Water stains or damage noted at soffits and exterior walls.
    • Water stains or damage noted at interior ceilings/walls.
    • Water stains or damage noted at roof sheathing/structure at roof edge, inside attic.
    • Specialized roof components have been installed to attempt to prevent ice damming leakage.
    • Heating cables have been installed at the roof.

Potential causes of ice damming.

    • Intricate roof design which may cause poor water drainage.
    • 1 storey houses and townhouses are susceptible to ice damming.
    • Lower sloped/long sloped roof, allowing water time to freeze on roof.
    • Insufficient insulation/ventilation of attic/roof spaces can promote snow melt on roof.
    • Cathedral ceiling designs can reduce insulation or ventilation levels.
    • Inefficient window/door seals allow heat to escape, facilitating snow melt on the roof above those components.
    • Location of roof components (plumbing vents, skylights) may block/slow water drainage.
    • Changes in roof slope will slow water drainage promoting ice build-up.
    • Eavestrough downspouts discharging to lower roof can cause water back-up/leakage.
    • Dirty/clogged eavestrough gutters and downspouts will slow water drainage from roof.

Recommended course of action.

    • Your roof should be monitored closely for ice damming after heavy snowfalls.
    • Proper insulation, ventilation and good roof maintenance can help reduce the risk of ice dam build-up.
    • It is recommended that roof snow and ice build-up be removed to prevent leakage. This type of work should only be done by qualified professionals.

The most important factor of prevention is the proper ventilation of your attic or roof spaces.

Copyright (2003) CBCG – Reprinted with permission.