Ice dams are common in homes that have poor attic ventilation, and they can cause a massive amount of damage to your roof. Ice dams form on the edges of a roof when outside temperatures are below freezing and you have the heat on in your home.
Heat rises up to the attic, where it warms the roof above it through thermal conduction. The edges of your roof, however, are still below freezing — they're not above your attic, so the high temperatures in your attic don't warm them up. Snow that falls on the center of your roof will melt, and then it will run downhill until it reaches the edge of the roof and freezes again. This forms an ice dam that traps melted snow, keeping it on your roof instead of allowing it to run off.
The trapped water on the edges can cause considerable damage to a shingled roof. To learn how ice dams can damage a roof and how the damage can be repaired, read on.
How Do Ice Dams Damage a Roof?
The worst way that ice dams can damage your roof is by causing your roof sheathing to rot. Ice dams slowly melt when they're exposed to sunlight, and the melted ice will leak downwards. Water can sneak underneath a shingle and begin to move uphill towards the center of your roof due to capillary action. Water underneath your shingles can saturate your wooden roof sheathing, and this will cause it to rot. In addition, saturated roof sheathing also typically leads to water leaking into your attic, which can ruin your insulation by getting it wet or lead to mold growth.
In addition to rotting your roof sheathing, ice dams can also do serious damage to your shingles. Shingled roofs are meant to shed water quickly, and they don't hold up well to the standing water at the edges of the ice dam caused when melted snow becomes trapped there. The adhesives holding the shingles together will begin to dissolve, and this makes them more likely to fly off of your roof during a severe storm. Water making its way uphill underneath your shingles can also refreeze underneath them, and the pressure caused by the expanding ice can pull shingles off of your roof.
How Do You Repair Damage Done by Ice Dams?
If you notice ice dams forming on the edges of your roof, have your roof inspected by a professional roof repair service. A contractor will pull up the shingles on the edge of your roof in order to inspect the sheathing. If melted snow has caused the sheathing to rot, it will need to be replaced. Rotted sheathing loses much of its strength, and leaving rotted sheathing in place can eventually lead to the edges of your roof collapsing under the weight of snow and shingles above it.
A roof repair service will also inspect your shingles for signs of damage. Any shingles that have become unglued will need to be replaced in order to boost your roof's wind resistance — the adhesive holding them together makes them much stronger during storms.
Afterward, you'll need to prevent ice dams from forming again. The best way to do this is to add more vents to your home's attic. More ventilation will keep attic temperatures cooler, which stops high attic temperatures from causing the snow on your roof to melt and form ice dams. You also have the option of installing a long drip edge around your roof, which keeps any ice dams far away from your shingles, reducing the likelihood that your roof will be damaged by them.
