Ice Dams in Gutters and Other St. Louis Winter Damage
St. Louis winters aren't Minneapolis winters. Snow comes and goes, and there are usually a few mild days in January. That's exactly the problem. Ice dams in gutters, split downspouts and sagging runs here come less from one deep freeze than from repetition: a gutter freezes, thaws, refills and freezes again dozens of times between the first hard freeze in late November and the last one in March. Each cycle does a little damage. Here's where it lands, and what to check when it's over.
What water does when gutters freeze
Water expands by about nine percent when it freezes. In a gutter that's holding an inch of water because the pitch has gone, that expansion presses outward against the corner seams and end caps, and the sealant — which has been baking on the south side all summer — cracks. In a January thaw the corner drips. Refreeze, and the crack widens. By March the corner that was fine in October is open.
Frozen gutters also carry weight. Water is a little over eight pounds a gallon; a 5-inch K-style gutter holds roughly 1.2 gallons per foot when full, so a 40-foot run frozen solid is carrying around 400 pounds. Spike hangers that were already backed out a quarter inch let go. Hidden hangers on 24-inch centers hold; on 36-inch centers, the gutter bows between them and never quite comes back straight.
How ice dams in gutters form
Heat leaks from the house into the attic, warms the roof deck, and snow on the roof melts from underneath. The meltwater runs down to the eave, which sticks out past the warm wall and is cold, and refreezes there. A ridge of ice builds up, water pools behind it, and backs up under the shingles into the sheathing, the soffit, and eventually the ceiling below.
The gutter is where the dam shows because the gutter is at the eave, but the gutter didn't cause it, and taking the gutter off wouldn't stop it. The lasting fix is in the attic: air sealing around the top plates, can lights and the attic hatch, then insulation. A 1960s ranch in Hazelwood with old batts is a classic case. Heat cables treat the symptom on houses where the attic can't be fixed; gutter heat cables in St. Louis goes through when that's the right call.
What to look for: a few icicles on gutters after a snow are normal. A thick shelf of ice along the whole eave with icicles below it, on a roof that still has snow above, is a dam.
Downspouts
Water that reaches a downspout during a thaw and freezes in the bottom elbow before it gets out builds up from the bottom. A downspout can freeze solid to the top. When it does, the seams split — usually at the bottom elbow, sometimes along the length — and you won't see the split until the spring rain runs out the side. North-side downspouts on two-story homes are the usual victims. A 3x4 downspout tends to clog with ice less readily than a 2x3 because there's more room for water to keep moving.
Gutter damage from snow, and the fascia behind it
Heavy, wet snow sliding off a steep roof can bend the front lip of a gutter or pull a run forward off its hangers, especially on spike-hung systems. That's the most visible kind of gutter damage from snow. The less visible kind is behind the gutter: meltwater running down from a missing drip edge, or from a dam, soaks the fascia and freezes in it. Wet wood that freezes and thaws repeatedly breaks down. A few winters of that and the board that looked fine is soft, and eventually the ice-loaded gutter takes it off the house. That's why a fascia check belongs on every gutter repair visit, and why soft boards are better replaced before winter than after. The roof-edge side is covered in water running behind gutters.
Guards in winter
Screens and micro-mesh are fine if the gutter under them drains. A solid reverse-curve hood on a shaded eave grows a row of icicles off its lip and holds ice against the shingle edge; that's a design trait, not a defect, and it's one reason those hoods are a poor fit under St. Louis winters. Gutter screens vs gutter guards compares the types.
The March inspection
When the last freeze is done, usually mid-March, walk the house after the first good rain and look for:
- Drips at corners that didn't drip in October
- A run that now sags between hangers, or a gap at the back
- Water running out the side of a downspout at the bottom elbow
- Fascia paint that's bubbled or lifted in a band along the eave
- Water stains on a ceiling near an outside wall — that's a dam that got in
- A gutter that no longer holds its fall, with a tide line where water sat
Any two of those on a 1980s or 90s aluminum system are worth a ladder look. Ice dam gutter repair is usually modest — resealing corners, re-hanging a run, replacing a split downspout — but if the list is long, repair vs. replacement has the rule for deciding what comes next.
Going into winter well
Most of what ice does, it does to a gutter that went into December holding water or leaves. Empty, pitched, sealed and strapped, an aluminum gutter here comes through winter in good shape year after year. The before-the-freeze list is in how to winterize gutters, and the last dry week of November is the time to finish it.
What to do during a hard freeze
Most of the time, the right move is to do very little. Ice on a gutter is not an emergency by itself. Here's a short list for the cold weeks:
- Look, don't climb. Check the eaves from the ground after each snow. A ladder on ice is the most dangerous part of any winter.
- Clear the downspout bottoms. Kick snow away from extensions and splash blocks so meltwater has somewhere to go in the next thaw.
- Watch the ceilings. A stain near an outside wall means water got past the shingles. Photograph it with the date.
- Rake the roof edge only if you can do it from the ground. A roof rake with a long handle can pull the lowest few feet of snow off a single-story eave. Never stand on the roof.
- Write down what you see. Which eave grew icicles, which downspout froze, which corner dripped. That list is your spring work order.
Comparing repair quotes after winter
If the March walk turns up damage, get the work in writing before anyone starts. A useful quote names each item: which corners get resealed, how many feet get re-hung and on what hanger spacing, which downspouts get replaced and at what size, and how many feet of fascia, if any, are soft. Two quotes that list the same items are easy to compare. A quote that only says "winter repairs" is not. If one contractor says the whole system is done and another says three corners and a downspout, ask each to show you why.
Common questions
How do you prevent ice dams in gutters?
Keep heat out of the attic first: seal the air leaks into it and add insulation where it's thin, so the roof deck stays cold. Then make sure the gutters are clean and pitched so meltwater drains instead of sitting. Heat cable is a fallback for eaves where the attic can't be reached.
Should you knock icicles off gutters?
Small icicles can be left alone; they usually drop on their own in a thaw. Knocking big ones off from below is a safety risk and can bend the gutter lip or tear hangers loose. If icicles are large and constant along one eave, treat that as a sign of an ice dam and look at the attic.
Why do ice dams form on some houses and not others?
It mostly comes down to how much heat reaches the roof deck and where the sun hits. Houses with poorly sealed attics, can lights in the top-floor ceiling or finished attic rooms are prone to them, as are shaded north eaves. Two identical houses on the same street can behave differently because of insulation and attic venting alone.
Is it safe to use salt or a hammer on frozen gutters?
Neither is a good idea. Chipping ice dents the gutter and can crack seams and shingles, and rock salt corrodes metal and can damage plants below. If a gutter or downspout is frozen solid, let it thaw and fix the cause, or ask a contractor about calcium chloride products made for roofs.
Does homeowners insurance cover ice dam damage?
It depends on the policy and on what was damaged. Water that comes through a ceiling is handled differently from a gutter that pulled off the house. Check your policy or ask your agent, and photograph the damage with dates before anything is repaired.
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