Every February, Edmonton roofs grow a ridge of ice along the eaves and homeowners start finding water stains on upstairs ceilings. The ice is the visible part. The cause is two metres above your bedroom ceiling.
The mechanism
It takes three things, and Edmonton supplies all three for months at a time:
- Snow on the roof.
- A roof deck warm enough to melt the underside of that snow. Heat escaping from the house into the attic.
- An eave that stays below freezing. The overhang has no heated space beneath it, so it is always colder than the rest of the roof.
Meltwater runs down the warm section, reaches the cold eave, and refreezes. That ice grows into a dam. Water then pools behind it — and since it cannot run down, it runs sideways and upward, under the shingles, which are designed to shed water flowing downhill and nothing else. From there it goes through the sheathing into the insulation, the ceiling, and the top of the exterior wall.
Why your neighbour's roof is fine and yours is not
Identical houses behave completely differently, and the reason is always attic heat. The usual culprits:
- A bathroom fan venting into the attic instead of through the roof. Warm, wet air directly onto the deck. Extremely common in older Edmonton houses.
- An unsealed attic hatch. A large, permanent hole in your ceiling.
- Recessed lights and gaps at top plates. Dozens of small heat leaks that add up.
- Blocked soffit intake. Frequently caused by blown-in insulation added later without baffles — an energy upgrade that created a roofing problem.
- Insufficient or compressed insulation. 1970s and 1980s depths are well short of what keeps a deck cold now.
- Unbalanced ventilation. Exhaust vents at the ridge with no matching intake at the soffit cannot move air. Both halves are required.
What to do right now, if there is ice on your roof
- Do not chip at it. Hammers and axes break shingles and flashing, and the repair costs more than the removal.
- Do not use salt or ice-melt tablets. They corrode flashing and fasteners and kill whatever is planted below.
- Do use a roof rake from the ground to pull snow off the lower metre or two. Removing the fuel stops the dam growing.
- Do call for steam removal if water is already entering. Low-pressure steam melts ice without damaging the roof. It is the only safe method.
- Do not go up a ladder onto an icy roof. Please — and see what is and is not safe to do yourself.
The permanent fix, in order of effectiveness
- Seal the attic bypasses. Hatch, fan ducts, light fixtures, plumbing stacks, top plates. Cheapest and most effective single step.
- Vent bathroom and kitchen fans outside — through the roof or the wall, never into the attic.
- Restore soffit intake and install baffles so insulation cannot block it.
- Top up insulation to current standards, keeping it clear of the baffles.
- Balance exhaust ventilation at the ridge to match the intake.
- Extend the ice-and-water membrane at the next re-roof so it runs well inside the heated wall line. This does not prevent dams; it stops the water getting in when one forms.
Heat cables belong at the bottom of this list. They manage the symptom, cost money to run every winter, and are a reasonable answer only where a roof geometry genuinely cannot be ventilated properly.
Is the damage covered?
Resulting water damage is often covered on Alberta policies. Insurers resist where the cause is clearly poor maintenance — blocked vents, a known problem left alone. Document the event promptly, keep mitigation receipts, and keep the emergency work separate from the ventilation improvements, which are an upgrade to your house rather than a claim.
What to do about it, in order
If there is ice on the roof and water inside right now, steam removal comes first — see ice dam roof damage for what that involves and why chipping and salt make it worse. Where the water has already tracked into a ceiling, roof leak repair finds the actual entry point rather than the wet drywall. The permanent fix is an attic and ventilation job done in better weather, and if the roof is coming off anyway it is the cheapest time to correct the membrane at the eaves — see roof replacement.