Most homeowners call a roofer after a leak shows up inside. By then the decision is usually already made. But a lot of roofs get replaced before they need to be, and plenty get patched when they shouldn’t. What a contractor sees when they get on the roof is what drives that call.
What a roofer checks
The age of the shingles matters, but it’s not the whole picture. An architectural shingle roof in Ontario installed properly should last 25–35 years. A 3-tab roof lasts closer to 15–20 years, and most of those installed in the 1990s or early 2000s are past their expected life now.
When a contractor gets on the roof, four things determine which way the conversation goes.
Granule loss first. Asphalt shingles shed granules as they age; you’ll see them in your eavestrough. Heavy granule loss across a large portion of the roof means the UV-protective coating is gone. The shingles will fail within a few years regardless of the calendar.
Cupping and curling next. Shingles that cup (edges bent up) or curl (corners lifted) are no longer lying flat. Water pools, ice dams form more easily, wind gets underneath. Spot repairs here are temporary.
Surface cracking and bare spots tell a different story depending on where they appear. Scattered across multiple areas, they point to systemic wear. Concentrated in one section, they’re more likely impact or installation damage, and repairable.
Sheathing condition is the one that doesn’t show up in photos. If the decking underneath has soft spots, rot, or delamination, every shingle on top is on borrowed time. A quote that skips the sheathing inspection isn’t a complete quote.
The repair-vs-replace math
A repair makes sense when damage is isolated: a section hit by a falling branch, a few shingles lifted by wind, flashing failure around a chimney or vent. When the surrounding surface is in reasonable shape, a targeted fix holds up.
A replacement makes more sense when repairs would cover more than 25–30% of the surface, when the shingles are near the end of their expected life, or when the sheathing has deteriorated in multiple locations. Patching a 20-year-old 3-tab roof extends its life by two or three years, not ten.
Cost difference in Ontario: full replacement on a standard 1,500–2,000 sq ft home runs $10,000–$18,000 for architectural shingles, with GTA labour rates pushing the high end. A targeted repair runs $400–$1,500 depending on scope. The math only favours repair when you have at least 8–10 years of useful life left in the surrounding surface.
Ice damming in Ontario
Ice dams form when heat escapes through the roof deck, melts the snow above, and refreezes at the cold eaves. The water backs up under the shingles. In older homes with inadequate attic insulation, this causes interior water damage on a structurally sound roof.
If you’re seeing ice damming every winter and interior staining near the eaves, replacing the shingles without addressing the insulation and ventilation underneath won’t solve it. A contractor who only talks about shingles without asking about your attic is only covering half the job.
Before you sign
Ask who is listed as the permit holder, and whether they’re pulling one. Some municipalities require permits for full roof replacement; your contractor should know whether your job triggers that.
Ask what happens if they find rotted sheathing mid-job. Get the per-sheet replacement cost in writing. Typically $60–$120/sheet installed, a compromised deck adds $1,500–$3,000 to the total.
Ask about the ventilation plan. New shingles over inadequate ventilation voids most manufacturer warranties and leads to early failure.
Ask whether the existing ice and water shield is being removed or covered. Ontario code requires it on the first metre from the eaves; some contractors skip it to save time. That last one is worth asking directly, because it’s easy to miss in a verbal walkthrough and it’ll matter in five years.
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