# What causes a gutter ice dam, and can gutters prevent it?

> What a gutter ice dam is, why it starts at the roof and attic rather than the gutter, how ice damages gutter hardware, and what to do in a rare Kent freeze.

URL: https://guttersofkent.com/guide/gutter-ice-dams/

An ice dam is a roof problem that shows up at the gutter. In Kent, where snow is light and infrequent, the more useful question is usually whether the ice damaged the gutter on its way out.

Short answer

An ice dam forms when heat escaping through the roof melts snow, and the meltwater refreezes at the colder roof edge and in the gutter. Gutters do not cause ice dams and cannot prevent them; the cause is attic heat loss and ventilation. What gutters can suffer is the damage: bent runs, pulled hangers and split joints from ice weight.

Key takeaways

- Ice dams start on the roof: attic heat melts snow, and the water refreezes over the cold eave.

- The fix for the dam itself is insulation, air sealing and ventilation, not a different gutter.

- Gutters can be damaged by ice weight, frozen outlets and snow sliding off a steep or metal roof.

- Kent sees light snow, about 6.3 inches a year at SeaTac, so ice damage is occasional rather than seasonal.

## An ice dam is a roof problem that ends at the gutter

A gutter ice dam is a ridge of ice that forms along the roof edge and in the gutter, holding back meltwater that can then back up under the shingles. [Gutters of Kent](https://guttersofkent.com/) installs and repairs gutters across Kent and South King County, with the work done by licensed and insured contractors, and with ice dams the honest starting point is that the gutter is where the problem shows up, not where it begins. The cause is on the roof and in the attic. What a gutter installer can address is the other half: the damage ice does to gutter hardware, and the details that let water drain once it thaws.

## How an ice dam forms

Snow on a roof acts as a blanket. Where heat escapes from the house into the attic, through gaps in insulation, air leaks around light fixtures and hatches, or a poorly ventilated attic, it warms the roof deck from below. Snow on the warm part of the roof melts, even when the outdoor air is below freezing. The meltwater runs down the roof until it reaches the eave, which overhangs the wall and stays at outdoor temperature. There it refreezes.

Each cycle of melting and refreezing builds the ice ridge higher at the edge. Water arriving from above then pools behind the ridge, and because shingles are designed to shed water running downhill, not to hold standing water, it can work up and under them into the roof deck, the wall and the ceiling below. Icicles along the gutter are the visible sign of water reaching the edge and freezing there.

## Why gutters do not cause or cure ice dams

A gutter full of ice is part of the dam, which is why gutters get blamed. But the ice in the gutter is the end of the process, not its cause. A house with a cold, well-ventilated attic can carry snow on the roof and never form a dam, gutters or not. A house losing heat through the ceiling can form one with no gutter at all, at the shingle edge.

That means no gutter size, profile or guard prevents ice dams. The lasting fixes are attic insulation, air sealing and roof ventilation, which are roof and attic work. Roof and attic work is not offered, so where a house has a recurring ice-dam history, that part is for a roofer or insulation contractor.

Heat cables are another approach some homeowners use: electric cables laid in a zigzag along the roof edge and in the gutter and downspout to keep a melt channel open. They are electrical work, which is not offered, and they treat the symptom rather than the heat loss behind it.

## What ice does to gutters

Separate from the roof problem, ice can damage a gutter in several ways:

- **Weight.** A gutter packed with ice, with icicles hanging from it, carries a load close to that of a full gutter of water, but it holds that load for days instead of draining it in minutes, and icicles add weight beyond the front lip. Hangers bend, fasteners pull out of the fascia and the run sags or tips forward. A gutter already on loose spikes or soft wood is the one most likely to give way. The [guide to why gutters sag](https://guttersofkent.com/guide/why-gutters-sag/) explains the support chain.

- **Frozen outlets and downspouts.** Ice blocks the outlet or the bottom elbow, so meltwater cannot leave. It backs up in the gutter, refreezes and adds weight. Water that freezes inside a downspout can split its seams.

- **Split joints.** Water freezing in a corner or end cap expands and can open the joint. The leak shows up after the thaw. The [guide to leaks at corners and seams](https://guttersofkent.com/guide/gutter-leaking-at-corner-or-seam/) covers the repair.

- **Sliding snow.** Snow sliding off a steep roof, and especially off a metal roof, can strike the gutter or shear it off. On metal roofs, snow guards on the roof and the way the gutter sits below the edge matter more than in other places; see [gutters for metal roofs](https://guttersofkent.com/metal-roof-gutters/).

| What you see after a freeze | Likely problem | Who addresses it |
| --- | --- | --- |
| Ice ridge on the roof edge, leak inside the house | Ice dam from attic heat loss | Roofer or insulation contractor (not offered) |
| Gutter bent or pulled away after ice | Ice weight on hangers or soft fascia | Gutter repair |
| Corner or end cap leaking after the thaw | Joint opened by freezing water | Gutter repair |
| Downspout split or crushed | Water froze inside | Downspout repair or replacement |
| Gutter sheared off below a steep or metal roof | Sliding snow | Gutter repair; roof snow guards by a roofer |

## How often this happens in Kent

Not often. NOAA’s 1991 to 2020 normals for SeaTac, the nearest station with snowfall records, show about 6.3 inches of snow a year, falling mostly in December, January and February at under 2.5 inches a month, and roughly 1.9 days a year with an inch of snow or more. The station averages about 25 days a year with a low below freezing, but most of those nights do not follow a snowfall that stays on the roof. The Kent station does not publish a snowfall normal.

In practice, that means ice in Kent gutters is an occasional event, usually a few days after an unusual snowfall followed by a cold snap, rather than something that builds all winter. It also means a house can go years without seeing it, and then have one bad week. The heavier risk for gutters here is the long rainy season, not snow; NOAA’s Kent normals show about 40 inches of precipitation a year, mostly from October through January.

## What to do during a freeze

When ice builds up, the safest choices are usually the passive ones:

- Stay off icy ladders and roofs. A ladder against a frozen gutter is a poor anchor.

- Keep people and cars out from under large icicles.

- Point downspout discharge away from walks and drives, where meltwater refreezes into a slip hazard.

- Avoid chipping ice out of the gutter with tools, which dents and punctures the metal.

- Note any leaks inside the house, with photos and dates, in case they need to be reported to your insurer; the [guide to insurance for gutter damage](https://guttersofkent.com/guide/gutter-storm-damage-insurance/) explains how storm damage is usually treated.

## After the thaw: checking for damage

Once the ice has gone, look for the signs it left behind: a run that dips or has tipped forward, hangers bent or loose, a gap between gutter and fascia, a corner or end cap now dripping, or a downspout with a split seam or a crushed elbow. Water stains on the fascia or soffit point to water that got behind the gutter while it was frozen.

Most of this is ordinary [gutter repair](https://guttersofkent.com/gutter-repair/): re-hanging a run on hidden hangers into sound wood and pitching it toward the outlets, resealing or replacing a split joint, and replacing a damaged section of [downspout](https://guttersofkent.com/downspouts/). Where hangers have pulled out of soft wood, [gutter and fascia repair](https://guttersofkent.com/gutter-fascia-repair/) comes first, and [sagging gutter repair](https://guttersofkent.com/sagging-gutter-repair/) covers runs that have dropped. A water test then runs water through the critical corners and outlets and confirms each downspout carries it away. If the damage is spread along the house, the [repair vs replacement guide](https://guttersofkent.com/guide/gutter-repair-vs-replacement/) helps weigh the options.

If the house had an ice dam that leaked inside, the gutter repair is only half the job: the attic and roof side needs a roofer or insulation contractor. When you want the gutters checked after a freeze, [Get an Estimate](https://guttersofkent.com/contact/), or use the [problem checker](https://guttersofkent.com/tools/gutter-problem-checker/) to sort what you see.

Questions about your own house? Call [(253) 352-5321](tel:+12533525321) or get an estimate.

## More questions on this topic

### Should I pour hot water into a frozen downspout?

It rarely helps for long. Hot water can melt a channel, but in freezing weather it often refreezes lower in the downspout or at the bottom elbow, adding to the blockage. Do not climb an icy ladder to chip at a gutter. In Kent, freezes usually break within days, and checking for damage after the thaw is the safer course.

### Do gutter guards make ice dams worse?

Guards do not cause ice dams, which start with roof heat, but they vary in how they behave in snow and ice. Some covers can hold a layer of snow or ice on top, and some let ice form inside the trough beneath them. For a house with a history of ice at the eaves, that behavior is worth asking about before choosing a guard.

### Can icicles on my gutters damage them?

Heavy icicles are a sign of water freezing at the edge, and their weight adds to the load on the hangers. A few small icicles after a cold snap are not a concern. Large ones hanging from a gutter that is also full of ice can bend the run or pull hangers loose, and they are a hazard to anyone below.

## Keep reading

[Why are my gutters overflowing? Read the guide](https://guttersofkent.com/guide/why-are-my-gutters-overflowing/)[Why is water running behind my gutters? Read the guide](https://guttersofkent.com/guide/water-behind-gutters/)[Why do gutters sag? Read the guide](https://guttersofkent.com/guide/why-gutters-sag/)[Why is my gutter leaking at the corner or seam? Read the guide](https://guttersofkent.com/guide/gutter-leaking-at-corner-or-seam/)[Gutter repair vs replacement: which does your house need? Read the guide](https://guttersofkent.com/guide/gutter-repair-vs-replacement/)