How do I prevent ice damming from damaging stucco near the roofline in Ottawa?

Ice dams are a serious concern for Ottawa stucco homes, and the damage they cause often goes unnoticed until it's extensive. When heat escapes through the roof, snow melts and refreezes at the eaves, creating a dam of ice that forces water upward under shingles and sideways into the stucco at the roof-wall junction. In a city that averages 175 cm of snowfall, this isn't a rare event — it's an annual battle.

Protecting Stucco from Ice Dam Damage

Address the root cause — attic insulation and ventilation. Ice dams form because the roof deck is too warm. Ontario Building Code requires minimum R-50 attic insulation for Ottawa (Climate Zone 6), but many older homes have R-20 or less. Upgrading attic insulation costs $1,500–$4,000 for a typical Ottawa bungalow and is the single most effective way to prevent ice dams. Ensure soffit vents aren't blocked by insulation — baffles should maintain airflow from soffit to ridge.

Proper flashing at the roof-stucco junction. This is where most ice dam damage to stucco actually occurs. You need:

• Step flashing woven into shingle courses, extending at least 100 mm up behind the stucco's weather-resistive barrier- A kick-out flashing at the bottom of every roof-wall intersection to direct water into the gutter- Counter-flashing or a metal drip edge over the top termination of the stucco- A 50 mm minimum clearance gap between the stucco surface and the roof — stucco should never touch shingles

Ice and water shield membrane. Install a self-adhered ice and water shield (like Grace Ice & Water Shield) on the roof deck extending at least 900 mm (3 feet) past the interior wall line. OBC requires this in Ottawa. At roof-wall junctions, this membrane should extend up the wall sheathing at least 300 mm. This is your last line of defence when ice dams do form.

Heated cable systems. For chronic problem areas — valleys, dormers, and roof-wall junctions — heat cables can prevent ice from forming. Professional installation with self-regulating cables (which adjust power output based on temperature) runs $500–$1,500 per problem area in Ottawa. These are especially worthwhile on complex rooflines where multiple surfaces channel snowmelt toward stucco walls.

Gutter maintenance and sizing. Clogged or undersized gutters accelerate ice dam formation. Ottawa gutters should be cleaned in late November before the first major freeze and inspected in spring. Consider oversized 6-inch gutters at roof-wall junctions where water volume is concentrated. Gutter guards rated for snow loads ($8–$15 per linear foot installed) reduce debris buildup.

Snow management. After heavy snowfalls, use a roof rake to pull snow off the lower 3–4 feet of the roof near stucco walls. This removes the fuel that creates ice dams. A quality roof rake costs $40–$80 at Ottawa hardware stores and pays for itself the first season.

If ice dam damage has already occurred — look for horizontal cracking, staining, or soft spots in the stucco near the roofline — get a professional assessment before winter. Repairs to damaged stucco and flashing typically run $1,500–$5,000 in Ottawa, but catching it before water reaches the sheathing and framing can prevent far more expensive structural work.

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• 613Bins
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• Transitions Renovations
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• DC Stucco & Parging

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