Roof Inspection and Snow Load Management Before a Canadian Winter

A roof that performs adequately through summer can reveal hidden vulnerabilities the moment snow begins to accumulate in November. Shingles that lift slightly at the corners, flashing that has pulled away from a chimney, or an attic with blocked soffit vents can all lead to water intrusion once the freeze-thaw cycle begins. Conducting a visual inspection in September or October — before the first significant snowfall — is the best opportunity to address problems while access is straightforward and repair contractors are available.

Visual Inspection: What to Look For

A thorough pre-winter roof inspection covers the surface materials, the edges, and the transition points where different systems meet. From ground level with binoculars, and where accessible from a safely placed ladder, the following items should be assessed:

Shingles

• Curling or cupping: Asphalt shingles that curve upward at the edges or develop a concave shape in the middle have passed their service life. They are susceptible to wind lift and ice penetration.
• Missing granules: Patches of bare asphalt visible on shingles, or heavy granule accumulation in gutters, indicate shingle aging. Granules protect the asphalt from UV and physical wear.
• Cracked or broken sections: Physical cracks allow water to wick under the shingle above. Even minor cracks become pathways for ice.
• Missing shingles: Absent shingles must be replaced before winter. Even a single missing shingle over a valley or penetration can allow significant water entry.

Flashing

Flashing — the metal strips installed at all roof penetrations and transitions — is a common site of winter failures. Check:

• Flashing around all chimney bases, skylights, and vent pipes
• Step flashing along dormers and sidewall junctions
• Valley flashing where two roof planes meet
• Drip edge condition at eaves and rakes

Look for lifted edges, missing sealant, rust staining, or sections that have pulled away from the adjacent roofing. Any gap wider than 1–2 mm requires attention before freeze-up.

Gutters and Eave Condition

While gutter clearing is covered in detail in the Gutter Clearing guide, the eave condition is relevant to roof inspection. Ice dams form most aggressively at the eave line. Check for any signs of staining or deterioration on the fascia boards, which can indicate chronic overflow or ice dam damage from previous seasons.

Ice Dams: Cause and Prevention

Ice dams are ridges of ice that form at or near the roof eave. They develop when heat escaping from the living space warms the upper portion of the roof deck, melting snow above the insulated area. The melt water flows downslope until it reaches the cold eave overhang — which is not warmed by indoor heat — where it refreezes. As the dam grows, water pools behind it and can back up under shingles.

The root cause of ice dams is almost always one of two things: insufficient attic insulation or inadequate attic ventilation, or a combination of both.

Surface treatments such as calcium chloride or zinc strips may reduce ice buildup once it has begun, but they address the symptom rather than the cause. Improving attic insulation and ventilation is the durable solution.

Snow Load Considerations

The National Building Code of Canada specifies design snow loads for structures based on geographic location and roof geometry. Residential roofs built to code should be able to handle typical snow accumulations for their region. However, older structures, additions built without permits, or roofs with flat or low-slope geometry may warrant attention when snowfall is heavy or prolonged.

Indicators that accumulated snow load may be approaching a concerning level include:

• Difficulty opening or closing interior doors — a sign the structure is deflecting under load
• Visible bowing or sagging of the ridge or rafters (observable from the attic)
• Cracking sounds from the attic during heavy accumulation

If these signs appear, consult a structural engineer or contractor. Mechanical removal of snow from a roof is a common practice in high-snow regions of Canada, but it carries fall risk and can damage roofing materials if done incorrectly. Roof rakes — long-handled tools that allow snow removal from ground level — are available at hardware stores and are preferred for routine clearing.

Attic Inspection Alongside Roof Work

The best complement to an exterior roof inspection is a brief attic inspection. From the attic, look for:

• Daylight visible through any point in the roof deck — an unambiguous indication of a gap
• Water staining on the underside of the deck or on structural members
• Frost on the underside of the deck in cold weather — a sign of excessive moisture and insufficient ventilation
• Adequate insulation depth uniformly distributed across the floor (not piled up against walls)

When to Involve a Professional

A homeowner visual inspection is useful for identifying obvious problems, but it has limitations. A licensed roofing contractor can walk the roof surface safely, probe suspected areas for soft spots, and evaluate flashing integrity up close. If the roof is more than 15–20 years old, has not been professionally inspected in the past several years, or shows any of the shingle conditions described above, a professional assessment before winter is a practical precaution.

References and Further Reading

• Canada Mortgage and Housing Corporation – Home Maintenance
• Natural Resources Canada – Attic and Roof Insulation