3 Examples of the Freeze/Thaw Cycle at Work on your Roof

Ice on a Roof about to Melt

If you live in an area where the daily temperature range in winter runs above and below freezing, there is a good chance that one or more forms of the freeze/thaw cycle is at work on your roof. Here are 3 examples.

Ice dams:

  • The cause – Ice dams form through uneven heating of a roof that is holding an accumulation of snow. In most cases, uneven heating is the result of heat radiating through the attic of the structure while the area over the eaves stays much cooler. If the difference between these two areas is great enough, snow over the attic will melt and drain toward the eaves where it refreezes; forming a ledge that subsequently collects runoff that is trapped over the warmer part of the roof.
  • Potential damage – Trapped water can back up under shingles and saturate roofing materials, which speeds the deterioration process. If the process is far enough along, trapped water can start leaking into the structure. If an ice dam and the amount of water trapped behind it become large enough, roof damage may also result from bearing the excess weight of ice and water.
  • Solution – If you see evidence of the formation of an ice dam, such as a preponderance of icicles, call a professional for immediate removal. To prevent ice dams, add insulation to your attic to reduce the heating of the roof.

Small spaces between roofing materials:

  • The cause – Water finds its way in to spaces between roofing materials, which can occur when it pools behind an ice dam. If this water freezes in these spaces, its expansion can push roofing materials apart by microscopically small distances at first.
  • Potential damage – Given enough time, these tiny movements can allow increasing amounts of water into the space to freeze, expand, melt, and repeat. This can ultimately lead to a significant weakening of the roofing system.
  • Solution – Handle ice dams as quickly as possible and conduct regular inspections to address issues as quickly as possible.

The gradual separation of flashing from the chimney, vents and other structures that penetrate the roof deck:

  • The cause – Flashing, which is purposed for channeling water away from roof penetrations, can start cracking and or separating from vents, chimneys, ducts, etc., which provides the opportunity for water to enter.
  • Potential damage – Much like the freeze/thaw cycle in spaces between roofing materials, frozen water gradually makes these deficiencies larger, thus allowing more water to enter, which facilitates more damage.
  • Solution – Inspect flashing regularly and seal any cracks that appear. If flashing is damaged, call for immediate repairs.

The damage of a freeze/thaw cycle on a roof can be subtle at first, but significant later. If you live in an area that regularly experiences freezes and thaws, the best courses are to take preventative actions where possible and inspect your roof regularly.