A roofing job might look fine from the ground, but bad roofing job warning signs are often hidden in the details that only a trained eye can spot — or that only become apparent when the first heavy rain arrives. Whether you are inspecting a roof that was recently installed by another contractor, evaluating a home you are considering purchasing, or checking your own contractor’s work, knowing what to look for protects you from costly repairs and premature roof failure.
Warning Signs Visible from the Ground
- Uneven or wavy shingle lines: Properly installed shingles create straight, uniform horizontal lines across the roof. Wavy, crooked, or inconsistent lines indicate rushed installation, improperly aligned starter courses, or shingles installed over an uneven deck surface without correction
- Mismatched shingle colours: If sections of the roof appear slightly different in colour or texture, it may indicate shingles from different production lots, partial repairs using different products, or leftover materials from another job
- Visible nail heads: Roofing nails should be completely concealed under the overlapping shingle above. Exposed nail heads indicate nails placed too high (above the nailing line), and each exposed nail is a potential leak point
- Missing or damaged drip edge: Metal drip edge should be visible along the eaves and rakes — it directs water into the gutters. Missing drip edge allows water to wick under the roof edge, causing fascia rot and ice dams
- Sloppy flashing: Flashing around chimneys, walls, vents, and skylights should be clean, tight, and properly layered. Visible caulk used as a substitute for proper flashing is a major red flag — caulk is a sealant, not a waterproofing method
Warning Signs on the Roof Surface
| Problem | What It Means | Risk Level |
|---|---|---|
| Nails through shingle face | Nail gun set too high, missed nailing strip | High — every face nail is a leak point |
| Overdriven nails (nail heads breaking shingle) | Nail gun pressure too high | High — shingle not properly secured |
| Missing ice and water shield at eaves | Code violation in Ontario (required 3ft up from eave) | Critical — ice dam leaks guaranteed |
| No underlayment visible at edges | May have been omitted or installed incorrectly | High — no secondary water barrier |
| Improper valley construction | Cut valleys without ice/water shield, open metal valleys with poor overlap | High — valleys carry concentrated water |
| Reused flashing from old roof | Cost-cutting — old flashing has reduced lifespan | Medium-High — weakest link in new roof |
| No kick-out flashing at wall/roof junctions | Water enters wall behind siding | Critical — causes hidden wall rot |
Warning Signs from the Attic
The attic reveals what the roof surface conceals. After any roof installation, check the attic space for: daylight visible through the deck (indicating gaps or missed areas), nail tips protruding excessively through the sheathing (indicating nails too long), evidence of new water stains on the underside of the deck (indicating installation-related damage), and blocked soffit vents (shingle debris or insulation pushed over vents during installation). A professional roofer should never block ventilation during installation.
What to Do If You Find Problems
- Document everything with photos and written notes
- Contact the installer with specific, documented concerns — give them the opportunity to correct their work
- Get an independent inspection from a different qualified roofer (The Roof Technician provides second-opinion inspections)
- Check the warranty: Most manufacturer warranties are void if installation does not meet their specifications
- File a complaint: If the contractor refuses to address legitimate deficiencies, file a complaint with the Ontario Consumer Protection office
How can I tell if my roof was installed properly?
What are the most common roofing mistakes?
Get an Expert Second Opinion — Call The Roof Technician
Call (416) 985-4328 or book an inspection.