Are Icicles a Sign of an Ice Dam?

Perhaps you saw them around the holidays: white or blue outdoor lights that simulate trickling icicles. Or greeting cards that depict houses with large icicles hanging from the gutters. While the frosty stalactites may look pretty, they may actually be a signal of trouble in your own home.

Are icicles a sign that something is amiss?

Icicles are commonly thought to be a sign of an ice dam on your roof, but are they? Possibly, says Rem Brown, senior engineering manager at the Insurance Institute for Business and Home Safety (IBHS).

The 3 things necessary to form icicles are also necessary to form ice dams.

The three things necessary to form icicles – snow, heat to melt the snow, and cold weather – are also necessary to form ice dams, he explains. Ice dams form when warm air from inside your home melts snow on the roof. When the meltwater reaches the colder eaves (the part of the roof that extends beyond the walls), the water re-freezes and creates a build-up of ice along the edge of your roofline.

So, icicles hanging from the roof edge could be a sign of an ice dam (and larger icicles would likely indicate a larger ice dam, Brown says), but ice dams can even form without the presence of any large icicles.

The more snow and ice accumulate, and temperatures rise and fall, the larger the potential for ice dams.

The dangers of ice dams

The more snow and ice accumulate, and temperatures rise and fall, the larger the potential for ice dams. And ice dams can wreak havoc. They can damage and loosen shingles, rip off gutters and cause meltwater to pool and seep into your attic. Once that happens, insulation can get wet, paint can peel and the structure of your home can become damp. Untreated, this may cause rotting wood, damaged drywall and even mold growth.

How to remove snow to avoid an ice dam

It’s best to remove snow from a heavy snowfall immediately to prevent the buildup of ice dams later. Though you might hear about people doing anything from using a snow blower to remove snow or an axe to chip away at an already-formed ice dam, both methods can damage your roof, IBHS warns.

A push broom with stiff bristles can be used to remove snow off flat and low-slope roofs, while a roof rake is the right option for sloped roofs, IBHS says, because you can remain on the ground and still remove snow. Of course, if you’re unable to easily reach the roof, or just unsure about your ability to do so, ask a roofing professional to do the job.

In the event that an ice dam does form, IBHS suggests keeping the attic well ventilated – the colder the attic, the less melting and refreezing on your roof, IBHS says.

How to permanently prevent ice dams

According to This Old House, the best way to prevent ice dams is to keep your roof and eaves the same temperature. Here’s how:

Add extra insulation in your attic floor to keep the warm air inside your home and out of the attic.

Relocate or remove heat sources (recessed lighting, for instance) in the attic directly under your roof.

Insulate attic access doors with a cover, or seal an existing hatch with weatherstripping.

Check the exhausts.Make sure all ducts from bathrooms, kitchens or other living areas exhaust to the outside, not the attic.

Check the flashing around the chimney. Over time, flashing can crack and separate from the roof, causing hot air to escape and allowing water to trickle in along the chimney. Have your chimney sweep check the flashing and, if necessary, repair or replace it.