Why do I have Ice on my Roof?

On my brief drive from home to the office there is one house in particular that gets an epic icicle between its South facing roof and the peak above their front door. Every year the icicle gets so big it eventually touches the ground, and then it continues to grow thicker and thicker each day. I think last years must have been two feet wide. Last year when I noticed it, I thought it was just because of all the ice storms, but this year we haven't had an ice storm, yet the icicle is still just as big. Lots of houses in my neighborhood (built in the 60's) do not have icicles, but lots of old homes in the East Hill have plenty of them.

Why are some houses cursed to always have these dangerous, heavy, precarious formations on their house, but I get away without having them? Sometimes the reasons are as innocent as the architectural characteristics of the roof, or the colour of the roof (although my roof is black which absorbs the most light, and still doesn't form icicles). A majority of the time, icicles and ice dams indicate that something is wrong. Reasons like heat loss, poor ventilation, and air leaks can all cause ice formation, and unfortunately, they can be a big deal. These formations can hurt someone if they happen to fall, but they can also cause a great deal of damage to your house if not kept in check.

Icicles and ice dams can cause water damage to your attic, house, insulation, drywall, and electrical. This damage may affect your aesthetic features too, such as peeling paint, bubbled drywall, or cracked or crumbled plaster. If the water damage is not rectified, you may also get mold and mildew, and structural decay as a result. The weight of the ice alone can be enough to compromise the structural integrity in some cases.

How to deal with it:

1.) I will chisel it myself- It is dangerous to go up on your roof to chisel the ice away. I do not recommend it as you risk damaging your roof. The bigger risk, of course, is your safety. You don't know how little or how much it will take for a large piece of ice to break free. Standing on a ladder underneath an ice dam your are chiseling at poses a highly dangerous scenario for you and anyone nearby. You probably don't want to be standing on an ice dam either, as they are slippery and could give way under your feet.

2.) Salt pucks- Easy to use, not that great or effective though. These are large pucks of salt that get thrown up on the roof on or near the ice. In my experience I only ever see them melt a hole into the ice and nothing else happens. I worry about where all the water goes that did manage to melt. It probably just froze again near the eaves when it cooled, making the ice build up bigger. Maybe they do help loosen up ice, but it would have to be when temperatures are above freezing or else the water just freezes again.

3.) Heat Tape- Works but costs about $600 a roll, needs to be installed, and puts penetrations all over your roof. Heat tape is only practical for poorly planned architectural characteristics in your house, like entry way roof valleys.

4.) Shoveling the roof- If there is no snow there to melt, you generally won't get ice build up. It's just a pain in the a** to do, which is why I would sooner do a preventative approach like numbers 5-10 instead.

5.) Make sure kitchen and bathroom fans vent directly outside, not into the attic. Excess moisture and heat into the attic are what cause the snow on top of it to melt then refreeze.

6.) Make sure your attic insulation is sealed- You might be insulated well, but you will still get air leaks if you haven't sealed the insulation.

7.) Make sure your attic is insulated- Loss of heat into attic = melting snow that turns to ice.

8.) Make sure your attic is ventilated- No ventilation means that the heat and moisture will stay trapped in the attic.

9.) Keep the temperature in your house lower. No matter how well insulated, ventilated, and sealed your attic is, if your heat is cranked, your going to lose some of it, and it might be problematic for your roof. I'm not saying you have to wear your winter clothes inside your house, I am just saying don't crank it so it feels like Bermuda while you are at work for nine hours.

10.) Insulate chimneys and flues within the attic space. If not, they will radiate heat throughout your attic, ventilation or not.


Buy a melt sock specially designed for such purposes, or fill a nylon full of calcium chloride so the melting ice can be directed downwards off the roof. Think of it as a water wick and try to get it directed to the eaves or as close to them as possible. You should remember that wherever the melted ice (that's water!) gets, there is a chance it will cool back to ice when it reaches it's destination which might still be on your roof, which is why using salt pucks is lunacy in most conditions.

Now that you have ruined your wife's nylons by filling them with salt and putting them on your roof for all your neighbors to see, maybe think about getting rid of the heat and moisture that is obviously in your attic with ventilation, insulation, and sealing, and to remember to check flues, chimneys, and exhaust fans for heat loss too.

Tell your wife, I'm sorry about the nylons.

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