Rooftop Snow & Ice Build-up


The Ottawa and Eastern Ontario region is well known for being in the snow belt. Sometimes, the heavy build-up of snow on roofs requires removal for reasons of weight, and sometimes because a heavy blanket of snow can lead to ice dams. Below is an explanation of the formation of ice dams on roofs and how best to deal with it:

  • The attic directly above the heated house is warmer than at the eaves. Uneven melting and freezing causes ice dams. Snow on the upper portions of the roof continues to melt at the shingle surface. This water trickles down to the colder roof edge where it freezes, forming an ice dam.
  • A poorly ventilated soffit results in even greater temperature discrepancy where the roof overhangs the exterior wall, even if there are plenty of vents on the rooftop. Air should enter at the soffit, flow up into the attic and out the rooftop vents to equalize the attic temperature.
  • Ice buildup prevents water from flowing off the roof and causes pooling. Shingles are not made to hold water, they are meant to shed water. During a rapid thaw or winter rain, trapped water seeps under shingles & into the roof. Shingles only have a 1” overlap when counting the cut-out slots.
  • Low pitch roofs pool greater quantities of water. Chimneys, pipes, vents, valleys and other roof intersections increase the likelihood of ice dam problems. Older homes, even when steep, are more susceptible to ice damming because soffits are generally very poorly ventilated.
  • Some roofs have the protection of a waterproofing ice shield membrane under the shingles along the eaves. The membrane offers protection only where it is installed and when nothing intersects it. A 3′ wide membrane at the eaves will not help if the ice dam goes back 4′ or if there is a chimney intersecting the membrane. (Err on the side of caution; order more protection.)
  • What to do? As a preventive measure, have the snow removed before an ice dam forms. Snow removal, if done carefully, using plastic scoops does not generally present a danger of serious roof/shingle damage. Vents may be more easily damaged, but are easily replaced.
  • If you have ice build-up already, and are worried (and you should be), first get the snow removed from your roof. This cuts off the water supply preventing further ice build-up and leaks.
  • Ice removal should be avoided unless it really becomes a serious problem. Ice removal has greater potential for damaging shingles & roof substrates, especially if very cold outside or if the buildup is very severe. To minimize damage in really cold weather, have channels cut into the ice at 5 to 10 foot intervals to allow water to drain off the roof. However, if the problem is very serious, all the ice may need to be removed. Mild weather is the best time for ice removal. On flat roofs, avoid ice removal unless the concern is weight tolerance!!
  • One must understand that, without ice removal, if there are more major snow storms on the way, you will be back to the original problem. Timing is a crucial factor, and often difficult to gage.
  • It is not advisable to remove only 3 to 6 feet of snow along roof eaves. Usually, a new ice dam forms right at the location in which clearing of snow was stopped. Leaks become even more likely because there is usually no ice shield protection under the shingles at that height on the roof.
  • Generally, there is little danger of roof collapse except on large flat roofs. Sometimes, falling ice can present a danger on steep steel or slate type roofs. The real problem is leakage. Roofs themselves will not sustain much damage from ice buildups or from leaks. However, house interiors – drywall, paint, furniture, expensive art objects, etc. will see the damage – and the “big bucks”!!! If 5 to 10 shingles are damaged due to ice removal, it will be relatively simple and inexpensive to have those changed come spring. Not so for interior water damage.
  • Your home insurance, depending on the type of policy, may cover you for interior damage, but usually not for snow & ice removal. Even properly installed roofs will leak with extensive ice build-up. Warranties by roofing companies are very unlikely to cover for ice & water backup. In short, the homeowner should take reasonable precautions.
  • ROOFMASTER provides an emergency snow & ice removal service. If holding a roof warranty from us, we urge you to call us when you are in need of such roofing services, rather than risk voiding your warranty. We’re committed to providing fair rates & quality service to our past clients. Please call us for details or questions.