Why Roof Inspection Timing Matters

Most roof damage from winter conditions becomes visible only after the damage has already occurred — water stains on ceilings appear after an ice dam has allowed melt water to penetrate under shingles; sagging occurs after structural members have absorbed moisture over multiple seasons. Inspection conducted in October or early November, before the first significant snowfall, allows problems to be addressed while roofing contractors have availability and materials can cure properly before freezing temperatures arrive.

Safety note: Physical inspection of a roof surface should not be attempted by homeowners during or immediately after snowfall, or when temperatures are below 0°C and frost may be present. Most of the checklist below can be conducted from inside the attic and from ground level using binoculars. For close examination of flashing and valleys, hire a licensed roofing contractor.

Exterior Inspection — Ground Level

Shingle Condition

From ground level with binoculars, examine each roof slope for:

  • Curling or cupping at shingle edges, which indicates moisture absorption and accelerated ageing
  • Missing shingles — even a single missing shingle over a valley allows water ingress with every rain and melt event
  • Granule loss visible as dark patches or as granule accumulation in gutters during cleaning
  • Shingle cracking or brittleness, which appears as a pattern of small transverse cracks across the shingle face

Asphalt shingles in Canadian climates have a design life of 20–25 years for 3-tab and 25–30 years for architectural (laminate) profiles, assuming installation was performed to manufacturer specifications. Roofs older than 20 years warrant a professional assessment before winter.

Flashing at Penetrations and Valleys

Ice and water infiltration occurs most frequently at flashing transitions — around chimneys, skylights, plumbing vents, and in valley sections where two roof planes meet. Examine with binoculars for:

  • Lifted or separated step flashing along chimney sides and dormers
  • Cracked or dried caulk at the counter flashing lap
  • Rusting or perforations in older galvanised flashing that has not been replaced to aluminium or copper
  • Standing debris in valley sections, which can trap ice and redirect melt water under adjacent shingles

Gutters and Downspouts

Gutters must be clear before freeze conditions arrive. Blocked gutters hold standing water that freezes to form an ice bridge extending up the roof slope, creating the initial condition for ice dam formation. Check that:

  • All debris (leaves, needles, granules) is cleaned from gutters and collected in the downspout basket
  • Downspouts are clear from top to bottom — run water through each spout with a hose
  • Gutter hangers are intact and the gutter section does not sag at mid-span, which allows pooling
  • Downspout extensions direct water at least 1.5 metres away from the foundation

Attic Inspection

Insulation Depth and Coverage

The primary driver of ice dam formation is heat escaping through the roof deck. When the underside of the roof deck warms above 0°C, snow on the roof surface melts; the melt water runs down the slope until it reaches the cold overhang, where it refreezes as ice. Adequate attic insulation keeps the deck at a temperature closer to ambient, reducing the melt cycle.

Natural Resources Canada recommends attic insulation of at least R-50 for most Canadian climate zones (Zone 6 and above, which includes most of Ontario, Alberta, Saskatchewan, and Manitoba). Check that:

  • Blown-in or batt insulation covers the entire attic floor without gaps or compressed sections near the eaves
  • Insulation does not block the intake airflow path at the soffit vents — baffles (also called rafter vents) should be visible at each rafter bay, maintaining a clear channel between the soffit and the ridge
  • Recessed light fixtures below the attic floor are sealed with rated airtight covers, as these are among the most significant sources of warm air and moisture infiltration into the attic

Ventilation Assessment

Balanced attic ventilation — equal intake area at the soffits and exhaust area at the ridge — maintains the attic temperature close to outdoor ambient. The standard ratio is 1 sq ft of free ventilation area per 150 sq ft of attic floor (some codes allow 1:300 with a vapour barrier). From inside the attic:

  • Confirm that soffit vents are visible as open passages, not painted over or blocked by insulation
  • Check that the ridge vent (or gable vents) are intact and free of bird or insect nesting material
  • Note any signs of frost on the underside of the roof deck or on rafter surfaces — this indicates that humid interior air is infiltrating the attic space and condensing, which will cause structural rot over time

Roof Deck Condition

While in the attic, inspect the underside of the roof deck (typically OSB or plywood) under good lighting:

  • Dark staining or soft spots at the deck indicate previous water infiltration; probe soft spots with an awl to assess whether the wood is sound or has begun to delaminate
  • Visible daylight through nail penetrations is normal; daylight visible through larger openings at ridge or flashing locations is not
  • Check all rafter connections at the ridge beam and at the top plate for any signs of separation or previous movement

Snow Load Considerations

The National Building Code of Canada specifies ground snow load values by location (Appendix C). Roof snow loads are derived from ground loads adjusted for roof slope and exposure. For flat or low-slope roofs (below 3:12 pitch), the roof snow load may approach 80–90% of the ground load.

In areas of British Columbia, Quebec, and the northern Prairies where ground snow loads exceed 2.0 kPa (approximately 200 kg/m²), flat or low-slope roof sections require periodic snow removal during multi-day snowfall events to remain within design load limits. A typical wood-frame residential roof is designed to a total load (snow plus dead load) of approximately 1.9–2.4 kPa. If snow accumulation exceeds 30–40 cm on a flat roof section and temperatures remain below −10°C (preventing self-consolidation), removal should be considered.

Roof rakes — long-handled tools with lightweight aluminium or plastic blades designed to pull snow from the edge of a pitched roof while standing at ground level — are the appropriate tool for most homeowners. They do not require ladder access and remove load from the most critical area: the overhang, where ice dams form.

When to Call a Licensed Roofer

The following conditions warrant professional assessment rather than DIY investigation:

  • Any visible sagging of the roof surface or ridge line
  • Water stains on upper floor ceilings that appeared or expanded during the previous winter
  • Roof age over 20 years without a professional inspection in the past five years
  • Ice dams that form annually in the same location, despite gutter maintenance
  • Any visible open flashing at chimney, skylight, or plumbing vent penetrations

In Ontario, roofing contractors should be registered with the Ontario College of Trades. In British Columbia, the BC Housing Licensing and Consumer Services registry covers residential roofing. Verify registration before signing a contract for repairs.

References and Further Reading