What Exactly Is an Ice Dam?
An ice dam is a ridge of refrozen melt-water that forms along the colder eaves of a roof. Once thick enough, it traps subsequent melt-water, which backs up under shingles and leaks into the attic.
Attribute | Detail |
Core cause | Warm roof deck + sub-zero eaves |
Typical thickness | 2 cm – 20 cm |
High-risk zones | North-facing eaves, shallow-pitch roofs, valleys |
GTA peak season | Late Dec – early Mar (freeze-thaw cycles) |
Why Ice Dams Form in Toronto Winters
- Escaping heat: Gaps in attic insulation allow household heat to warm the roof deck.
- Freeze-thaw loop: Daytime melts snow; night-time refreezes meltwater at eaves.
- Inefficient drainage: Clogged gutters slow runoff, giving water time to freeze.
- Insufficient ventilation: Stagnant attic air stays warm, fuelling thaw above and freeze below.
Early Warning Signs
- Long, thick icicles hanging from gutters plus a wet roof behind them.
- Attic moisture: Frost on roof-deck nails, damp insulation, or water stains on exterior ceilings.
- Uneven snow melt: Bare patches higher up while snow persists at eaves.
5 Proven Ways to PREVENT Ice Dams
Upgrade Attic Insulation (R-60 Target)
- Blow-in cellulose or closed-cell spray foam seals air leaks and holds heat inside the living space.
Improve Roof Ventilation
- Balanced soffit intake + ridge exhaust keeps roof deck below freezing, even when the house is warm.
Clear Snow With a Roof Rake
- After every 15 cm snowfall, rake the lower 1 m of the roof from ground level to remove fuel for thaw.
Keep Gutters & Downspouts Flowing
- Autumn leaf clean-out + spring flush ensure meltwater drains fast before it can re-freeze.
Install Heat Cables on Persistent Problem Areas
- Self-regulating heating cables along eaves maintain a melt-channel for runoff.
(Tip: Anta Plumbing partners with certified roofers to install CSA-approved cables.)
Safe DIY REMOVAL: Calcium-Chloride “Socks”
Never chop ice with a hammer—one slip can destroy shingles.
- Gear up: Non-slip boots, eye protection, ladder stabiliser.
- Rake a channel: Remove loose snow 1 m up from the eaves.
- Fill a nylon stocking with calcium chloride (NOT rock salt). Tie shut.
- Lay stocking perpendicular to the dam so it drapes over gutter edge.
- Wait 1–2 hours: Chemical melts a drainage slot; water begins to run out.
- Re-position as needed until the dam drains completely.
Protect shrubs below with a tarp—calcium-rich drip can burn foliage.
When to Call a Professional
- Ice dam > 10 cm thick or spans multiple storeys.
- Active ceiling leaks, bulging drywall, or attic mold growth.
- You lack safe ladder access or roof pitch exceeds 6/12.
Anta Plumbing offers 24/7 emergency ice-dam steaming and long-term roof-drainage upgrades across the GTA.
Eco-Friendly Alternatives
Method | Pros | Cons |
Steam removal (pro) | Fast, shingle-safe | Requires specialised equipment |
Hot-water pressure flush (pro) | Clears gutters & dams together | Uses 100–150 L water |
Roof-edge metal drip-edge | Prevents initial bond | Added material cost |
Frequently
Asked Questions
Often no—many policies list it as preventable. Check your wording for “freeze/thaw exclusion.”
Yes, but self-regulating cables only draw power near freezing (~30–40 W/m), adding <$8/month for a 15 m run.
Avoid it. Sodium chloride corrodes aluminum gutters and stained-wood siding. Stick to calcium chloride.
Steeper than 6/12 sheds snow quickly, but insulation and ventilation still matter.
Key Takeaways
- Ice dams start with warm attics + cold eaves—fix the heat loss first.
- Combine R-60 insulation, balanced ventilation, timely snow-raking, and clear gutters to prevent dams.
- Use calcium-chloride socks (never rock salt) to melt safe drainage slots if a dam forms.
- Large dams or active leaks? Call Anta Plumbing for steam removal and long-term roof solutions.
Winter Roof Trouble? Let’s Fix It.
Anta Plumbing’s team clears dams, installs heat cables, and upgrades attic ventilation—all winter long across Toronto and the GTA.
📞 Call 416-231-3331 or book a free attic inspection before the next thaw strikes.
