Curling or missing shingles
Shingles are the first line of defence against ice, wind, and meltwater. On a GTA roof more than twelve to fifteen years old, we routinely see edges that curl up, corners that lift, or full tabs missing along the windward slope.
Once a shingle curls, the asphalt mat underneath is exposed to UV and freeze-thaw cycles. From there, failure accelerates: one tab becomes five, five becomes a leak in the next ice storm.
- Curled or cupped tabs along ridges and eaves
- Bald patches where shingles have blown clean off
- Cracking visible from the ground after a hot summer
- Loose tabs you can lift with a finger
Compromised flashing
Flashing — the metal strips around chimneys, skylights, sidewalls, and roof valleys — is where almost every Toronto leak we diagnose actually starts. Shingles get the attention, but flashing carries the water.
Look for rust streaks, lifted edges, or caulk that has shrunk away from the substrate. Step-flashing along sidewalls is the most common offender: when it's installed under the siding rather than woven into the courses, every wind-driven rain finds its way behind.
| Flashing location | Common failure | What it leads to |
|---|---|---|
| Chimney | Counter-flashing pulls out of mortar | Top-floor ceiling stain |
| Valley | Open seams under shingles | Saturated decking, ice dams |
| Sidewall | Surface-caulked instead of woven | Wall cavity rot, siding bulge |
| Vent stack | Cracked neoprene boot | Drip onto attic insulation |
Interior ceiling stains
A brown ring on a top-floor ceiling almost never appears directly under the leak. Water tracks along rafters, insulation, and drywall before it stains — sometimes three to five metres from the actual entry point.
If you've seen a stain bloom, photograph it, note the date, and check it after the next heavy rain. If it grows, the leak is active. If a new stain appears in a different room, you likely have a second compromised area, not the same leak migrating.
- Yellow halo with a darker centre: active or recent leak
- Dry, faded brown stain that hasn't grown in a year: usually old, sealed
- Bubbled paint or sagging drywall: water is currently pooling above
Granule loss in gutters
Asphalt shingles shed a small amount of granule throughout their life — that's normal. What isn't normal is finding the bottom of your downspout filled with what looks like coarse black sand.
Heavy granule loss means the asphalt mat is exposed and the shingles are at end-of-life. Once that happens, UV cooks the mat directly and brittleness sets in quickly. We typically give a roof in this condition one to two more winters before localized leaks become widespread.
Sagging or soft decking
Walk a roof and you can feel decking that's gone soft underfoot — usually around valleys, chimneys, or low slopes where water has been sitting under the membrane. From the ground, look for a wavy or rippled silhouette along the ridge line, especially against a bright sky.
Soft decking is the most expensive issue on this list because the fix isn't shingles — it's plywood replacement, new ice-and-water shield, and re-flashing. The good news: we catch it on a diagnostic before snow load makes it dangerous.
- 01
Walk the attic with a flashlight; look for daylight or staining on rafters
- 02
From outside, check the ridge line against a contrasting background
- 03
If you see waves, do not put weight on the roof — book an inspection
When to act
The window for non-emergency repair in the GTA effectively closes around late November — once temperatures drop below roughly 5°C, asphalt sealant strips on new shingles can't activate, and many manufacturers void warranties on cold-weather installs.
If you've spotted any of the five signs above, the right move is a written diagnostic now, not a tarp call in January. A real diagnostic includes photos of the failure, a written scope, and a clear answer to the question every homeowner actually wants: repair or replace?
Filed under
Blue Knight Roofing
Building-envelope specialists across the GTA since 1999.
