Ice Dams in Kansas City

It takes three things at once: snow on the roof, a roof deck warm enough in the middle to melt it, and an eave cold enough to freeze the runoff. Kansas City gives us all three several times a winter. A few inches of snow, a couple of days in the twenties, and a house losing heat into its own attic is the whole recipe.

The part homeowners miss is that the sun is not doing the melting. If it were, the snow would come off evenly. When you see clear shingles up near the ridge and a thick white band along the bottom two or three feet, that pattern is heat from inside the house working its way up through the ceiling and into the attic. Snow is an excellent insulator, so it traps that heat against the deck and melts from the bottom up.

Water runs to the edge and reaches the overhang, which hangs past the exterior wall in open air and is heated by nothing. So it freezes there, and the next round of meltwater backs up behind that ice. Give it a week of the same weather and you have standing water sitting on a shingle roof.

Shingles overlap in one direction. They shed water moving down the slope and do nothing for water pushed sideways or uphill by a pond of ice. Once the dam is deep enough, water finds the seams between courses and follows the nail holes into the deck.

That is why the ceiling stain usually appears well after the storm has passed and often on a mild day. People call us convinced a tree limb hit the roof during the snow. Nine times out of ten nothing hit the roof at all.

The defense built into a modern replacement is ice-and-water membrane along the eaves and in the valleys. It is a self-sealing sheet that grabs around fasteners, and it is the reason a newer roof with a dam often stays dry inside while the neighbor's forty-year-old roof does not. Worth being clear about, though: the membrane limits the damage. It does not prevent the dam.

We start inside, because the roof is downstream of the problem. The first thing we measure is insulation depth at the outside walls, not in the middle of the attic. That perimeter is where coverage is thinnest and where a lot of the heat gets out, and it is also where insulation gets shoved around by anyone who has been up there running a cable or a vent line.

Next comes air leakage. Insulation slows heat; it does not stop moving air. Open gaps at the top plates, a pull-down attic hatch with no weatherstripping, recessed can lights, an unsealed chase around a flue or a bath fan housing. Each one is a small chimney pushing warm house air straight at the underside of the deck.

Then the ducts and the fans. A bath fan or a dryer terminating into the attic instead of through the roof or wall is something we find regularly, and it is a double problem: heat plus moisture. Finally we check soffit intake. If the baffles are missing and blown insulation has packed the eave solid, the coldest part of the roof gets no air, which is exactly where you need it.

Heat cable, zigzagged along the eave and into the gutter, keeps a melt channel open so water has somewhere to go. It runs on electricity all winter and it treats the symptom. On a steep, hard-to-reach section of an older house it can be the right call, and we will install it and tell you plainly that it is a manager and not a cure.

A roof rake, used from the ground with an extension pole, pulls the lower few feet of snow off before it can feed a dam. It works, and it is the cheapest thing on this list. Use the plastic-bladed kind, stay off the ladder, and do not try to scrape the roof clean down to the shingle.

Chipping ice off with a hatchet or a hammer is where winter roof calls turn into spring replacement quotes. Cold shingles are stiff, and the granule mat fractures under a direct blow. We do steam out dams when a house is actively leaking, because steam melts ice without touching the roof surface. Rock salt in a sock is another thing we get asked about: it will open a small channel and it will also pit aluminum gutters and kill the shrubs under the drip line.

The permanent work is almost always inside: air seal the ceiling plane, bring insulation up to a consistent depth all the way out over the wall plates, install baffles so soffit intake reaches the deck, and get every fan and duct terminating outside the building instead of into the attic.

Where the roof itself is part of it, we handle that at the same time. That means ice-and-water membrane extending up the slope from the eave, new drip edge, and flashing rebuilt at any wall or chimney where the backed-up water has already been getting in. If decking has gone soft from repeated soaking we show you the sheet before we replace it and the per-sheet price is in the written scope ahead of time.

We also tell people when their dam is not worth chasing. A shallow ridge on one north-facing gutter that has never leaked inside does not need three thousand dollars of work. If that is what we find, that is what we will say, and you will still get the photographs.