Ice Dams on Utah Roofs, and What Actually Stops Them

September 2026

The ridge of ice on your eave is a symptom, not the problem

Every February we get calls that start the same way. There is a bank of ice sitting on the front overhang, icicles hanging off the gutter, and a brown ring showing up on a bedroom ceiling. The homeowner has already decided the shingles failed. Nine times out of ten the shingles are fine and the trouble is happening in the attic, where nobody thought to look.

An ice dam is a heat problem wearing a weather costume. That sounds like a slogan, so here is what it means on your house.

How the ice actually forms

Snow falls and sits on the roof. Underneath the roof, in the part of the house you heat, warm air is rising. If that warm air reaches the underside of the roof deck, it warms the deck, and the deck warms the snow lying on it. The bottom layer of that snowpack melts. The water runs downhill, the way water does.

Then it reaches the overhang. The overhang hangs out past the exterior wall, so there is no heated room beneath it. That section of deck is the same temperature as the air, which in a Salt Lake valley February is well below freezing. The water arrives there and stops being water. It freezes.

Do that for three days and you have built a wall of ice along the eave. Now the meltwater coming down from above has nowhere to go. It pools behind the ice, backs up under the bottom courses of shingle, and starts looking for the nail holes and the laps. Shingles shed water running downhill. They were never designed to hold standing water against themselves, and standing water is exactly what an ice dam creates.

The water gets through, hits the deck, soaks the insulation, and shows up as a stain several feet inside the wall. By the time you see it, the water has been in the assembly a while.

Why the icicles are not the story

People fixate on icicles because you can see them from the driveway. Icicles by themselves are just water freezing as it drips off an edge, and a roof can throw a few on a sunny afternoon without anything being wrong. What matters is whether there is a solid mass sitting back on the shingles above the gutter line. That mass is the dam.

The tell that proves it is heat

Walk out after a snowfall and look at the roof plane. If the snow has melted off the upper two thirds and is still sitting fat and white on the overhang, that is heat escaping the house. A roof over a properly sealed, properly vented attic keeps its snow evenly, because the deck stays close to outdoor temperature top to bottom. On a really honest morning you can read the ceiling joists in the melt pattern: stripes of bare shingle with snow between them means the wood is bridging heat straight through.

The three things causing it, in order

When we go into an attic on an ice dam call, we are looking for the same short list on almost every house.

• Air leaks from the house into the attic. Can lights that are not sealed, a bath fan dumping into the attic instead of out through the roof, the gap around a furnace flue, the top of an interior wall that was never capped, an attic hatch with no weatherstrip. Warm moist air pours through those openings all winter.
• Insulation that gets thin right where it matters most. The top plate, where the ceiling meets the exterior wall, is the hardest place to insulate properly and the most important. Plenty of attics up here have good depth in the middle of the floor and almost nothing over that plate.
• Ventilation that is out of balance. Usually a ridge vent along the peak with soffit intake that is stuffed full of blown insulation. Exhaust with no intake does not move air. It just pulls from the easiest available source, which is the house below.

Those three are the whole mechanism. Fix them and the deck stays cold, the snow stays put, and there is nothing to melt and refreeze.

What does not fix it

Heat cables are the most common thing we find already on a house with a dam problem. A cable melts a channel through ice so water has somewhere to go. It does not stop ice forming, and it runs on your power bill every hour it is on. We will not tell you to rip a working cable off a roof, but know what you bought: a drain through the symptom, not a repair.

Chopping ice off with a hammer is worse. Cold asphalt is brittle, and a hatchet swung at a dam takes granules and shingle edges off with the ice.

A new roof, by itself, also does not fix it. Replace the shingles and change nothing in the attic and you have a newer roof with the same dam on it next winter. That one costs people real money.

If somebody looks at an ice dam and quotes you shingles without ever opening the attic hatch, get another opinion. The answer is not on the outside of the house.

What actually fixes it

The work happens in two places, and the order matters.

Inside the attic

Seal the bypasses first. Every hole between the heated space and the attic gets found and closed. Foam around the flue with the right rated material, gaskets or covers over can lights, the bath fan ducted all the way out through a proper roof or wall cap. Then the insulation gets brought up to depth and carried out over the top plate without blocking the airway at the soffit.

That last part is where baffles come in. A baffle, or a chute, is a piece of material stapled between the rafters at the eave that holds insulation back and keeps a clear path from the soffit vent up into the attic. They are cheap. They fix more roofs than most people would believe.

Then the venting gets balanced. Net free intake area at the soffit has to at least match the exhaust up at the ridge, and on an older house it usually does not. The fix is opening up intake rather than adding more exhaust.

On the roof, when it comes off

When a roof is being replaced anyway, that is the cheap moment to get the ice details right, because the deck is already open.

Ice-and-water shield is the membrane that matters here. It is a self-adhering sheet that seals around the shank of every nail driven through it, so even if water backs up over it, there is no path down into the deck. It belongs at the eave, in every valley, and around every penetration.

The measurement people get wrong is the eave coverage. The requirement is about how far the membrane runs past the interior wall line, not a flat number of feet from the edge. On a house with deep overhangs that is more courses than a builder might assume, and a crew working fast will run one roll and call it done.

While it is open, the ridge slot gets cut correctly, the soffit chutes get set, and any bath fan that was dumping into the attic gets a real duct and a real cap. None of that is glamorous. All of it is what keeps the ceiling dry.

Which houses get it worst

Some rooflines are just harder. A shallow pitch holds snow instead of shedding it. Valleys and dormers give water more places to slow down and freeze. Cathedral ceilings are the toughest: with no attic between drywall and deck, the airway in each rafter bay has to be right or there is nothing to fix later. North-facing eaves stay frozen while the rest of the roof drains, which is why one corner dams and the rest never does.

What to do this winter if you already have one

If water is coming into the house right now, that is a call to make today, not in April. Reach us at (801) 382-8898 and tell us water is active, because that moves you to the front of the schedule.

If it is just ice on the eave and nothing inside, you have time. The right move is getting somebody in the attic with a light while it is still winter, because winter is when the evidence is visible. Frost on the underside of the sheathing, rust rings on the nail points, a bath fan blowing steam into the insulation: those things are obvious in January and invisible in July.

We would rather look at it now and put a plan together for spring than tear a roof off in the cold. Get in touch through our contact page and we will come out.

Questions homeowners ask us about ice dams

Does a bigger gutter or gutter guard stop ice dams?

No. The dam forms on the shingles above the gutter, not in it. A gutter full of ice looks like the cause because that is where you can see the problem, but the water that froze there came from melting snow higher up the roof. Changing the gutter changes nothing about the heat that melted it.

My roof is only six years old and it is damming. Did the roofer do something wrong?

Maybe, maybe not. If the ice barrier does not run far enough past the interior wall line, or the ridge was vented without opening the soffit intake, then yes, the assembly was built in a way that lets this happen. But a perfectly installed roof over a leaky attic will still dam, because the roofer did not build your ceiling. Getting in the attic is how you tell which it is.

Will adding more attic insulation solve it on its own?

It helps and it is rarely enough by itself. Insulation slows heat moving through a surface. It does not stop air from pouring through a hole. If there is an unsealed can light or an open flue chase, warm air goes right past the insulation, and blowing another foot of material on top can actually make it worse by burying the soffit intake. Seal the leaks first, then insulate, then check the venting.

Is it safe to pull the ice off myself?

Standing on a ladder next to a loaded eave is how people get hurt, and hitting cold shingles with anything hard damages them. If a dam has to come down mid-winter, steam is the method that does not wreck the roof. Chipping and salt pucks both do harm.

Do metal roofs get ice dams?

Less often, because a metal surface sheds snow before a pack can build. They are not immune, though. A shallow metal roof over a warm attic will still melt from beneath, and when metal lets go of a load it lets go all at once, which is its own hazard over a walkway or a front door.

We would rather tell you it is the attic

Nobody here is going to sit in your kitchen and work a close on a roof you do not need. Plenty of the ice dam calls we go on end with us telling somebody their shingles have years left and the money belongs in air sealing and baffles instead. That is a smaller job and it is the honest answer.

If you want somebody to actually get up there and into the attic and then tell you plainly what is going on, call (801) 382-8898 or send a note through our contact form. We work the Salt Lake valley out of Salt Lake City, and we live under these same roofs.