Ice dams are a common homeowner’s nightmare in the winter whenever it snows, potentially causing major and costly water damage to your roof and even ceilings. Ice dams occur when snow on the roof melts slightly then refreezes when the runoff reaches the eaves, often in the gutters. When the day warms even slightly, the top layer melts but is unable to drain off properly, resulting in a pool of water up against the base of your roof. The water then often seeps under the roofing material, sometimes as much as 5ft or even 10ft up. Eventually, the water can work its way into your house’s soffits, walls, and even ceilings. When it comes to ice dams, an ounce of prevention is worth far more than a pound of cure.
Thoroughly clean out your gutters and downspout after the last leaves have fallen in your neighborhood, but certainly before the first snows of the season. Water will run more swiftly through cleaned gutters, giving it less time to freeze. Empty gutters also allow more room for ice and water to pool before it starts threatening your roof.
Try to purchase a roof rake or snow rake (a type of rake specially designed for cleaning your roof of snow) before the first snow of the season, then scrape the snow off your roof after each snowfall, or pay someone to come out and scrape the snow for you. This can also help avoid problems with the snow falling suddenly and possibly hitting someone when it comes loose as it melts. Unfortunately, snow rakes only work for single-story homes – they’re not long enough to reach a second floor, and you should never use a roof rake while standing on a ladder. Snow rakes work well if you experience heavy snows only rarely, but can be tedious to use.You will also need to be careful to not damage shingles since they can become brittle in the cold. Specially designed roof rakes are available for clearing snow off solar panels – standard roof rakes should not be used on panels as they can scratch the photorefractive surface.
If nothing else works, heat cables can help prevent ice dams as a fallback measure, especially if installed in the gutters and the downspout. Heat cables run over portions of the roof in a zigzag pattern, melting away ice and snow when turned on and can help if installed on a part of your roof particularly prone to ice dams. They might not prevent ice dams entirely, but heat cables can create enough of a channel for water to drain away, preventing some water damage.
Next time you need to replace your roof, also consider adding a special ice-and-water barrier under the shingles up to 3ft to 6ft from the roof’s edge. It will help with waterproofing, and the building codes in most areas now actually require an ice-and-water barrier to be installed under your roof. Your local building inspector will know how far up the barrier needs to extend in your region.
A Colder Roof
Generally speaking, ice dams form when the surface of your roof is above freezing, but the edges of your roof are below freezing. As hot air leaks from inside your house, it warms up your roof, often just enough to bring it right to the edge of freezing, creating the conditions in which ice dams can form. Many of the methods listed here can also reduce heat leakage, lowering your heating bill.
The average U.S. home loses about one-third of its heat through the ceiling and into the attic, and from there into the outside world. Most of that loss is due to leaks between the conditioned home and unconditioned attic. Unfortunately, air leaks are a hard nut to crack, since you usually have to go into the attic, pull back insulation, and plug any leaks by hand with foam, caulk, or other methods. Leaks usually occur around anything that penetrates the ceiling, like pipes, ceiling fixtures, access hatches, and others. Sealing leaks is ideally a cold-weather project since otherwise, your attic will likely be too warm.
Heat loss also occurs through inadequate insulation. How much insulation you need varies depending on where you live. Generally, blown-in cellulose and fiberglass will serve better in colder regions, since they leave fewer gaps. See our article on installing insulation for a more in-depth look at how much and what kind of attic insulation your home needs. You will also want to make sure that any insulation doesn’t block your airflow. Baffles usually prevent blocked airflow, though you will still want to check your soffit vents.
Adding attic ventilation to an unfinished attic will make the attic colder, keeping the roof from heating up. Attic ventilation can be complicated. Generally speaking, you need about 1 sq ft of vent (the actual openings, added together for total vent area) per 300 sq ft of ceiling area (the size of the attic floor), with half of the total vent area low on the roof and half high on the roof. Look at your existing vents to find the area of each (which should be stamped somewhere easily visible), then add the area of your existing vents together to find out how much you still need. Some roof styles are harder to vent than others. When in doubt, contact a qualified contractor for advice and guidance.
Also, whenever you make your home more airtight, double check your combustion appliances, including furnaces and most water heaters, for backdrafts. If your appliance isn’t drafting properly, it could be leaking deadly waste products into your home. If you suspect you might have a problem with back drafting, contact a licensed home inspector to check your house and combustion appliances.
What to Do If a Dam Forms
Sometimes even the best preventative measures can’t stop dams from forming. Try to carefully remove any forming ice from your gutters. If you have heat cables, they can also reduce the damage a building ice dam will do. The safest way to remove the ice entirely, though, is to hire a roofing company to use a steamer to remove any ice and snow. A steamer uses hot water at high pressure to melt the ice without risking the damage that an ice pick does.
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