Ice Dams: How They Form and Why They Destroy Roofs

Ice damming happens every winter in Nova Scotia, especially during freeze-thaw cycles. It’s one of the most misunderstood roofing problems, and unfortunately one of the most damaging if ignored.

Many homeowners think leaks during winter come from snowfall itself — but most winter leaks actually come from melting snow that has nowhere to go.

How ice dams actually form

An ice dam forms when warm air from inside your home melts snow on the upper part of your roof. The melted water runs downward until it reaches the colder eaves, where it refreezes.

Over time, this ice builds up like a wall. New melting snow has nowhere to drain, so it pools behind the ice and is forced under your shingles.

Why ice dams cause roof leaks

Shingles are designed to shed water that runs down the roof — not water that gets pushed backwards or sideways.

When water backs up behind an ice dam, it seeps:

• Under shingles
• Behind fascia boards
• Into roof decking and framing
• Down into your insulation and ceilings

This is why ice dams often lead to ceiling stains, attic mold, and long-term rot — not just a small drip.

Halifax-specific factors that make ice dams worse

Ice damming is more common here because of our mixed winter conditions. We don’t get constant deep freeze — we get warm days, cold nights, rain, and snow repeatedly.

Other local factors include:

• Poor roof ventilation in older Halifax homes
• Heavy wet snow common to the region
• Heat escaping through attics and top-floor ceilings
• Clogged gutters that trap refreezing water

Signs you’re dealing with ice dam damage

• Large icicles forming along eaves
• Ice ridges or thick frozen layers at roof edges
• Water dripping inside during warm winter days
• Brown ceiling stains or bubbling paint

Can ice dams be prevented?

In many cases — yes.

Proper roof ventilation, attic insulation, and clean drainage systems dramatically reduce ice dam formation. During roof replacements, we also install proper ice and water shield membranes to protect vulnerable areas.

But if your roof is already older or leaking, ice dams can still cause damage even with precautions in place.