Before Winter
Four things done in November prevent most of what goes wrong in February, and the first of them is the one everybody skips.
Short answer
Clear the troughs and the downspouts after leaf fall. Check and clear the discharge so water does not stand and freeze at the bottom. Check the hangers and the slope. And look at the attic, because the ice that forms in the trough comes from heat loss up there rather than from the trough.
The four jobs
Clear the troughs and the downspouts, after the leaves have finished dropping. The elbow at the top of the downspout is where the blockage usually is.
Clear and check the discharge: extensions in place, sloping away, no standing water at the bottom, and not discharging onto a path that will ice over.
Check the hangers and the slope while somebody is up there — a loose hanger or a reversed slope going into winter is a run that will be damaged by spring.
And look at the attic: soffit intake clear, bath fans going outside, insulation even, no frost on the sheathing.
The first three are an afternoon. The fourth is the one that actually determines how much ice forms.
And book the cleaning early, because the window between the last leaf and the first freeze is short and everybody wants it at once.
The attic is the real job
A clean trough still freezes if the roof above it is melting snow all winter. Clearing the trough stops the trough holding water and stops the blockage making it worse, and that is worth doing — but the volume of ice is set by the attic. If this is an annual problem, the attic is where the money goes.
Worth doing at the same time
Check the fascia for soft spots behind the trough, which is the thing that fails under ice load.
Check the soffit for gaps, which is how animals get in over winter.
Check the roof at the eave for lifted shingles and damaged drip edge.
Clear any valley that discharges into the trough, because a blocked valley is a dam.
Trim branches overhanging the roof, which reduces next year debris and removes the animal route.
And check that any heat cable from last year still works and is correctly routed.
What not to bother with
Chipping ice out of a frozen trough, which damages it and achieves little.
Pouring salt or de-icer into the trough, which corrodes it and runs onto the planting below.
A pressure washer in the trough, which is effective and tends to blow the sealant out of the joints.
Fitting guards in November on a trough that has not been cleaned.
Heat cable as the first measure rather than the last.
And leaving it until a warm spell in January, because by then the damage is done and the trough is full of ice.
Common questions
What is the most important fall job?
Clearing the troughs and downspouts after leaf fall and before the first freeze.
Does salt in the trough help?
No. It corrodes the trough and runs onto the planting below.
Why does it still ice up after cleaning?
Because the ice volume is set by attic heat loss, not by what is in the trough.