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How to prevent ice damming on my roof?

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Winter is here, so are the ice dams! Ice dams are a nuisance but inevitable in snowy areas of the country, but they can be reduced and even eliminated with proper insulation and venting.

What is an ice dam?

Ice dams are chunks of ice that is formed along the brims of a roof and prevents the melting snow (water) from draining off the roof. The water that backs up behind the dam can leak into a home and cause damage to walls, ceilings, insulation, and other areas.

What causes ice dams?

Ice dams are formed after a heavy snowfall when warm air in the attic causes the roof to warm and the snow to melt. Water running down the roof refreezes when it reaches the colder roof edge, forming chunks and rim of ice. This rim can grow, trap more water behind it, and bingo—you have a full-fledged ice dam. The dam grows as it is fed by the melting snow above it, but it will limit itself to the portions of the roof that average below 32F. The melted water trapped by the ice drip through the roof or attic, into your house, further causing mold and mildew that results in wet and stained ceilings and walls, and peeling paint.

The key to preventing ice dams is simply to keep your attic and roof cold. After a snowfall, a cold roof will have a thick blanket of snow. A warmer roof, however, will soon have clear spots where the snow has melted off, and may well have icicles hanging from the eaves.

Preventing and dealing with ice dams

Even in a snowy part of the country, it is possible to find homes that do not have ice dams. Ice dams can be prevented by controlling the heat loss from the home and keeping the roofs cold.

  • Take immediate and long-term action
  • Evaluate snow load
  • Roof and attic ventilation
  • Measure your attic insulation level
  • To keep your roof and eaves the same temperature.
  • Add extra insulation in your attic floor to help 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.
  • 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, the flashing may crack and separate from the roof, causing hot air to potentially escape and allowing water to trickle in along the chimney. Have your chimney or roofing professional check the flashing and, if necessary, repair or replace it.

Prevent heat leakage

In most cases, about one-third of the heat loss is through the ceiling into the attic. And most of that loss comes from air leaks caused by unblocked walls, gaps in drywall, and cracks around light fixtures, plumbing pipes, chimneys, and other ceiling penetrations. The bonus point here is, you’ll save energy and reduce both your heating and your air conditioning bills by stopping air leakage to mitigate ice dams. Air leaks can be tough to stop. Always wear a dust mask, a long-sleeved shirt and long pants to help prevent skin irritations caused by insulation.

Some roof types are not simple to vent, they are difficult, especially roofs with angled ceilings and no attic, roofs with skylights, flat roof dormers and low-slope roofs. Furthermore, assessing the venting is tricky on homes that have had aluminum retrofitted over old soffits. Even if you have persistent ice damming in one area, you might have to remove several aluminum sections to check the venting. 

Cold Roof Solutions

Another good way is to keep the roof cold to minimize ice dams. Upgrade attic insulation to about R-40, plug up air leaks to the attic and improve attic ventilation. However, whenever you make your home more airtight, check your combustion appliances (gas, oil or propane-fired water heaters, furnaces, etc.) for back drafting. 

A cold roof isn’t always a perfect solution because, with heavy snowfall, you may get ice dams anyway. Or ice dams may consistently form at the foot of the roof (the joint where two roofs meet at a right angle) because they fill with windblown snow. And some sections of the roof may be impossible to keep cold. You may have to rely on ice dam prevention products or the secondary strategies when a cold roof isn’t enough.

Required Materials for prevention of an ice dam:

  • Caulk
  • Expanding foam
  • Heat cables
  • Ice and water barrier
  • Insulation
  • Roof vent
  • Soffit vent

Secondary Ways to Stop Ice Dam Damage

Rake the snow off

Rake the snow off the roof with a special roof rake, install heat cables in ice dam-prone valleys or other spots, and to prevent leaks, add special ice-and-water barrier when reroofing.

Hire an energy professional

Hire roofing professionals who are eligible to deal with the heat transfer problem that creates ice dams.

  • The hired contractor must conduct a blower door test to evaluate your ceiling’s assessment. Often times, the professionals also may use an infrared camera to find places in the ceiling where there is excessive heat loss.
  • Do not repair interior damage until ceilings and walls are dry.
  • Interior repair should be done together with correcting the heat loss problem that created the ice dam(s) or the damage might occur again.

What to do if you already have an ice dam?

Ice dams themselves aren’t essentially a problem. It’s the leaks that make the most of the damage. You may not have to do anything if signs of ice dam leakage are not detected, either in the soffits on the outside or in the attic or ceilings. Then during warmer weather, make the most out of the prevention strategies discussed above.

If you have leakage from an ice dam and can’t rake the snow off the roof, the best possible approach to get rid of the ice dam is to hire a roofing company with trained professionals to steam it off. A steamer is like a pressure washer, except that the water is hot. Chipping the ice off with a hatchet or an ice pick can break or puncture the shingles, while an ice steamer will melt the ice away without damaging the roofing.

On a cautious note:

  • Anyone on the roof during the winter or performing works on the roof from below risks injury and may cause damage to the roof and house.
  • It is absolutely important to contact professionals to carry out these kinds of risk-filled jobs.
  • Whenever a house is tightened up, ventilation systems, exhausting devices and combustion devices must have enough air to operate safely and effectively.

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