The short answer
Gutters crack in winter because water standing in them freezes and expands, pushing against joints, end stops and the channel itself. A gutter that drains properly rarely suffers. The ones that split are usually blocked, laid without enough fall or already brittle with age. The fix is to cure the cause of the standing water and then replace or reseal the damaged lengths.
What happens inside the gutter
Water takes up more room as ice than it does as liquid. Inside an open gutter that has a little room to spread, so the ice may do no harm. Where the gutter is narrow, full, or closed in at a joint or downpipe, the expansion has nowhere to go and it pushes outward against the walls. That force is enough to split a seam, spring an end cap or crack a plastic section.
A frozen plug in the outlet makes things worse. Meltwater from the roof comes down behind it, backs up and freezes in turn, so the ice builds in layers. The channel fills, and the added weight bends brackets and drags the front lip downward.
The pattern shows up after a hard spell, and often only when the thaw arrives. Cracks that opened during the freeze begin to drip, a joint runs, or a length that looked straight is now bowed. Many people first notice a problem when water pours down the wall in the first wet day afterwards.
Why some gutters survive and others split
Debris comes first. A gutter packed with leaf mould holds water like a sponge, and the wet mass freezes solid. Our answer on what blocked gutters do to a house goes through the wider effects of letting a run silt up.
Fall comes second. A gutter that sits level, or dips in the middle, never empties completely. A permanent puddle that freezes every cold night tests the seams hard. The same applies to a run that has dropped because of a failing bracket or board.
Material and age come third. Old uPVC becomes brittle as the plastic ages under sunlight, and a section that was flexible when new can crack from a modest knock of ice. Cast iron is strong, but its joints depend on putty or sealant that dries out, and ice then opens the gap. Aluminium is more tolerant of the movement because the metal is ductile and the seams are sealed, although a badly supported run still bends.
Signs of ice damage to look for
After a freeze, walk round the house on a dry morning and look up at the gutters. Cracks at joints, split end stops and sections that have bulged are plain to see. Staining below a joint shows where a seam has begun to leak, and a green or dark line down the wall is the track of water that has been escaping for some time.
Check that the gutter still slopes toward the outlet by looking along the line from one end. A visible dip suggests that brackets have moved, and the board behind them may be wet. Look at the fascia near any leak as well. Our page on why a gutter sags lists what to check there.
Icicles are worth a thought too. A line of them hanging from the edge is common after a freeze, and by themselves are not a fault, but a thick, heavy curtain along a short length points to water spilling over the lip or leaking from a joint above.
What to do, and what not to do
Do not hack at ice with a hammer or a spade. A plastic gutter shatters under a blow, and a cast iron one can crack. Do not pour boiling water over a frozen outlet either, since the sudden heat can split plastic and the water refreezes lower down. Wait for the thaw, or use warm water from a safe height, and only if you can reach without overstretching. Working at height in icy conditions is a good reason to call someone in.
Once the ice has gone, the repair depends on what was damaged. A leaking joint can often be cleaned and resealed. A cracked length is cut out and replaced. A bent bracket is re-fixed or renewed, and an end stop is swapped. If the gutter has failed in several places, or if it is plastic that has gone brittle, replacing the whole run is more sensible than patching.
Prevention is straightforward. Clear the gutters in late autumn, check the fall, and fix any leak that is dripping onto the same spot, since a regular drip makes ice build up. Typical UK lifespans for plastic guttering are given as 10 to 20 years in one cleaning firm's guide, so a run well beyond that age is a candidate for replacement before the winter and not after.
Repair costs, materials and cover
UK guides put guttering at about £30 to £70 per metre and scaffold at £20 to £40 per square metre, according to MyBuilder's 2026 figures, and a fixed price from us arrives in writing after the survey. A short repair at low level costs a fraction of a full replacement.
If you are thinking of changing material, we compare the options in our answer on whether aluminium gutters are worth the extra. For the money side of a claim, our page on gutter damage and insurance explains what insurers tend to treat as weather damage and what they treat as wear.
Leaks and storm damage are dealt with first, and a gutter spilling water down a wall is worth reporting early. Once the thaw comes, check the joints and brackets, because ice expanding in a full gutter can split a union or pull a bracket loose. Browse the gutters, soffits and fascias hub for the rest of the roofline services.
