June 6, 2026 · 8 min read
The freeze-thaw cycle does the damage
Alberta does not just get cold, it swings. A February chinook can take us from minus twenty to above freezing and back within a couple of days, and that cycle repeats through the whole winter.
Water in a trough freezes on the cold side of that swing and expands as it does. Ice takes up more room than the water it came from, so it pushes outward on the trough walls and downward on the hangers. Multiply that by thirty or forty cycles a season.
Ice weight pulls hangers out of fascia
A run packed solid with ice is remarkably heavy. That weight is carried by hangers screwed into a fascia board that was never designed for it, and each freeze pulls them a fraction further out.
You do not see it happen. You see it in April when the run sags, the slope is gone, and it now holds water where it used to drain — which sets up a worse winter the following year.
Snow shedding off the roof
Steeper roofs shed snow in slabs, and a slab coming off a second storey lands on the trough below it. That is what bends front edges and tears sections loose in a single afternoon.
Where this is a recurring problem, snow retention on the upper roof does more good than anything you can do to the trough itself.
Ice dams start in a blocked trough
A trough full of wet leaves going into November holds water. That water freezes, backs up under the shingle edge, and starts the dam. Once ice is established at the eave it stays until spring, and every thaw adds a little more water behind it.
The underlying cause is usually warm air escaping into the attic, but a clean, empty trough removes the starting point. Cleaning before freeze-up is the cheapest ice dam prevention available.
What to do before freeze-up
Clean the troughs after the leaves are down, not in early October. Flush every downspout and confirm water actually exits at the bottom, not just at the top. Check that extensions are still in place and pointing away from the house.
Have loose hangers re-secured now rather than in spring. A hanger that is already half out will not survive the winter, and the run it is holding will take the rest of the system with it.
What to leave until spring
Do not chip ice out of a frozen trough. Aluminum is soft at minus twenty and you will punch through it or tear the seams — we replace trough every spring that was damaged by someone trying to save it in January.
Do not pressure wash or run hot water into a frozen system either. If ice is causing an active leak into the house, call us; there are safe ways to open a channel. Otherwise, note the problem and book the repair for when it thaws.