What Ice Dams Do to Gutters and Rooflines in Central Ohio

How an Ice Dam Forms

It takes three things, and Central Ohio supplies all of them most winters. First, snow on the roof. Second, heat escaping from the living space into the attic, which warms the underside of the deck and melts that snow from below. Third, an eave that stays cold, because it hangs past the heated part of the house. Meltwater runs down the warm section, hits the cold overhang, and refreezes. Repeat that for a few days and you have a solid ridge of ice at the roof edge with liquid water pooling behind it, held there with nowhere to drain.

What It Does to Gutters

Gutters take the worst of it because they are hanging right where the ice forms.

• Weight. Ice filling a gutter run is enormously heavy, and the fasteners were sized for water, not for a solid block that does not drain.
• Pulling away from the fascia. That load levers the gutter down and out, opening a gap between the gutter and the board it hangs on.
• Seam and end cap failure. Ice expands as it forms. Sectional runs come apart at the joints first.
• Bent hangers and dented troughs when a slab of ice finally releases off the roof above.
• Damaged downspouts, which freeze solid from the bottom up and then split.

A gutter that has been pulled loose over one winter will not drain correctly the next spring, which sets up the clog and overflow cycle that rots the fascia behind it. The failures compound.

What It Does to the Roofline

The water sitting behind the dam is the real problem. Shingles shed water that is running downhill; they are not designed to hold back standing water. Once the pool behind the ice is deep enough, water works up under the shingle courses by capillary action and reaches the deck. From there it soaks the sheathing, wets the insulation below, and shows up as a ceiling stain along an exterior wall, usually weeks after the thaw when nobody connects it to the ice. Repeated seasons of this delaminate the deck at the eave and rust the fasteners holding it down.

Why Central Ohio Gets Them Badly

Our winters are not the coldest, and that is exactly the problem. A consistently frozen climate keeps snow frozen on the roof. We instead get repeated freeze and thaw swings, days above freezing followed by hard overnight lows, which is the precise pattern that melts and refreezes the same snowpack over and over. Add the older housing stock across Bexley, Grandview Heights, and Upper Arlington, where attic insulation and ventilation were built to a different standard, and you have the ideal setup. Newer builds are not immune either, usually because recessed lighting, bath fans, and attic hatches leak heat straight into the attic.

What Actually Prevents Them

This is where most advice goes wrong. Ice dams are an attic problem, so the fixes that last are attic fixes.

• Air sealing first. Sealing the gaps where warm air leaks into the attic, around light fixtures, the attic hatch, plumbing stacks, and top plates, does more than anything else on this list.
• Insulation to depth. Bringing attic insulation up to current levels keeps the deck cold enough that the snow does not melt from below.
• Balanced ventilation. Intake at the soffit and exhaust at the ridge flushes out whatever heat does get through. Blocked soffit vents defeat this completely.
• Ice and water shield at the eaves. A self adhering membrane along the roof edge does not stop the dam from forming, but it stops the water behind it from reaching your deck. This goes on during a roof replacement and is standard on our installs.
• Keeping gutters clear going into winter, so meltwater that does reach them has somewhere to go.

What Does Not Work

Chipping at the ice with a hammer or a spade damages the gutter and the shingles underneath, and people fall doing it. Throwing rock salt on the roof corrodes metal flashing and gutters and kills whatever is planted below. Gutter guards are worth having for leaves, and our comparison of gutter guards covers which types hold up here, but they do not prevent ice dams and some designs give the ice more to grip. Heat cables can keep a channel open on a problem eave, but they are managing the symptom, they cost money to run every winter, and they are not a substitute for fixing the attic.

If You Have One Right Now

Do not go up there. From inside, check the attic along the affected eave for wet insulation and staining on the deck. From the ground, look for gutters visibly pulled away from the fascia and for water staining on the ceiling or the top of exterior walls. The safe immediate measure is clearing snow from the lower few feet of roof with a roof rake while standing on the ground, which removes the fuel for the dam. Everything else waits for the thaw, and then the roof edge, the gutters, and the attic all get inspected together, because by then you are looking at three connected problems rather than one.