Ice Dam Prevention Guide

Ice dams form when heat escapes from your attic, melting snow on your roof. The water runs down to the cold eaves and refreezes, creating a dam that traps water behind it.

Why Ice Dams Are Dangerous

• Water backs up under shingles
• Causes interior water damage
• Damages gutters and fascia
• Can lead to mold growth
• Shortens roof lifespan

The Three-Part Solution

1. Insulation

Your attic floor should have R-49 to R-60 insulation (varies by climate). This keeps heat inside your home and out of the attic.

2. Ventilation

Proper attic ventilation keeps the roof deck cold:

• Ridge vents at peak
• Soffit vents at eaves
• Minimum 1:150 ratio (1 sq ft per 150 sq ft attic)

3. Ice and Water Shield

Building codes require ice and water shield membrane:

• Minimum 3 feet from eave
• Recommended 6 feet or beyond exterior wall
• Full valley coverage
• Around all penetrations

Best Products for Ice Dam Prevention

Ice & Water Shield

• Grace Ice & Water Shield: Gold standard
• GAF StormGuard: High temp tolerance
• Owens Corning WeatherLock: Good value

Shingles

• Heavy architectural shingles (250+ lbs/sq)
• SBS polymer-modified for flexibility
• Sealed nailing strips

What NOT to Do

• Don't chip ice off roof (damages shingles)
• Don't rely on heat cables alone
• Don't ignore small leaks
• Don't block soffit vents with insulation