If you're experiencing excessive ice build-up over your eves or in valleys between roof faces, here's a few helpful hints:

1. Ensure you have adequate insulation over your upper-most ceiling (the attic floor).

2. Ensure that your insulation does not contact the roof deck, or block the soffit vents.

3. Ensure that your upper roof area has adequte vents, and that they are not obstructed.

4. Heater cables can help prevent ice damming, but if you're applying the cables after the snow and ice have already accumulated, place the cables only at the gutter, or lower-most portion of the eves. Higher placement may cause meltwater to accumulate behind an ice dam, worsening the situation.

5. If you decide to shovel some excess snow off your roof, exercise extreme caution - a fall off a roof can be fatal! Also, ensure that you are not scraping the surface of your shingles. Asphalt shingles are especially prone to damage by heavy foot-wear, and by shovelling or sweeping.

6. It is important that the gutters and downspouts are freely discharging meltwater. Gutters improperly sloped and/or not cleared of leaves and debris, can cause formation of ice dams rather quickly.

7. Ensure that downspout extensions are not frozen into the grass or soil.

See also: Ice Damming (includes photos)