Ice dams and winter roof damage around Knoxville

The NOAA Storm Events Database records heavy snow on more than 60 dates in the five Knoxville-area counties since 2006, plus ice storms in December 2010, March 2014 and February 2015. Ice dams form when snow on a roof melts from attic heat and refreezes at the cold eaves, so older homes with little insulation and steep mountain cabins are most at risk.

How ice dams form here

Short answer: heat from the living space warms the upper roof, snow melts, and the water refreezes at the overhang, where the roof is cold.

In the valley, it takes a real snow followed by cold nights. At higher elevations in Sevier and Blount counties, snow comes more often and stays longer, so cabins with heated living space under the roof, cathedral ceilings and little insulation are prone to ice dams.

What policies usually cover

Short answer: often the sudden interior damage and weight-of-ice damage; usually not ice removal or the cause.

• Water through ceilings and walls from an ice dam: often covered.
• Gutters, roof framing or a carport damaged by the weight of ice or snow: often covered under "weight of ice, snow or sleet."
• Limbs downed by an ice storm onto the roof: generally covered.
• Frozen pipes in an empty cabin: may depend on whether you kept heat on or drained the system; read the policy.
• Long-term leaks, rot and mold: often excluded.

When you find an ice dam

1. Photograph the ice and any interior damage with dates.
2. Rake snow off the lower roof from the ground.
3. Do not chip or hammer the ice.
4. Hire a pro with steam equipment for stubborn dams.
5. Catch drips and dry wet materials quickly.
6. Report interior damage promptly, and remember your policy's suit clause.

Prevention

• Air-seal the ceiling below the attic around lights, fans and chimneys.
• Add insulation, especially in cathedral ceilings and knee walls.
• Keep soffit and ridge vents open.
• When reroofing, ask for ice and water barrier at the eaves and valleys where required.
• On metal roofs, ask about snow guards over doors, decks and walkways.
• Clear gutters before winter.

Empty cabins and second homes

Ask someone to check a cabin after every snow or ice storm. Some policies limit coverage for damage to a home left vacant or unoccupied for a set period; check yours.

East Tennessee winter storms

Higher elevations in Sevier and Blount counties, including Gatlinburg and the areas around Townsend, get snow far more often than the valley. Cabin owners should check roofs and gutters after each snow, especially if the cabin is rented or empty for weeks at a time.

Insulation and air sealing

Ice dams start with heat escaping into the attic. Knox, Blount and the surrounding counties are in climate zone 4A, where ENERGY STAR recommends about R-60 in an uninsulated attic, or adding about R-49 if you already have 3 to 4 inches. Seal leaks around attic hatches, recessed lights, bath fans and chimneys too.

Ventilation

Air should come in at the soffits and leave at the ridge or roof vents. Keep insulation from blocking soffit vents, and make sure bath and dryer vents exhaust outside.

Metal roofs and snow

Snow slides off metal roofs suddenly and in large sheets, which can injure people and damage lower roofs, decks and gutters. Many cabins have snow guards for this reason. Keep walkways and parked cars clear of eaves after snow.

Removing an ice dam

• Don't hack at ice; you will damage the roof.
• Use a roof rake from the ground to pull snow off the first few feet, away from power lines.
• Calcium chloride in a stocking across the dam can melt a drainage channel. Don't use rock salt.
• Steam removal and ladder work are jobs for professionals.

Snow and ice weight

Wet snow and ice add weight to roofs, carports and porches. If a roof sags or you hear cracking, leave the area and call a contractor. Policies often cover collapse caused by the weight of ice or snow, subject to their terms.