Ice Dams
The freeze-thaw mechanism behind Minnesota's most common roof claim.
The freeze-thaw mechanism behind Minnesota's most common roof claim. This field guide is written for Lakeville and Twin Cities south-metro homeowners by Home Inspector Lakeville MN.
Ice dams are one of the most common and most damaging roof claims in the south metro. Understanding the mechanism explains why the fix is almost never "a better roof."
The mechanism
Heat escaping into the attic warms the roof deck and melts the underside of the snowpack. The meltwater runs down to the cold eave, refreezes, and builds a dam. Water then backs up under the shingles and into the ceiling and walls.
Why it is an attic problem, not a roof problem
The root causes are air leakage into the attic, insufficient insulation, and unbalanced ventilation — not the shingles themselves. Replacing the roof without addressing the attic just buys a new roof to damage. We inspect insulation depth, bypass sealing at top plates and can lights, and soffit-to-ridge ventilation.
What buyers should look for
Ceiling stains near exterior walls, deteriorated paint at the eaves, and ice buildup in winter photos are tells. On any south-metro home, ask what has been done to the attic, not just the roof.
The fix follows the cause
Because the cause is attic air leakage, insulation, and ventilation, the durable fix is air-sealing the attic floor, bringing insulation up to recommended R-value, and balancing soffit-to-ridge ventilation. Heat cables and roof raking manage the symptom; the attic work removes it. A buyer should ask what has been done to the attic, not just whether the roof is new.
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