The potential for ice dams increases significantly during heavy snowfalls. This is especially true for older homes because they tend to be inadequately, or poorly insulated. Modern homes can also have ice dam problems, but this is more likely to be due to the roof design. For example, if multiple roof slopes drain to one location, this will allow large amounts of water/drainage to collect at one location. This commonly results in ice buildup - due to the melting and refreezing of snow/water that occurs on the roof as temperatures change throughout the days and weeks.
When significant snowfalls occur, excess snow should be removed from roof edges to help prevent ice buildup from occurring. A roof rake is the most common tool used for this chore. Heating cable (heat tape) can also be installed - and this tends to be the most effective method for homes that have recurring ice dam problems. Heating cable warms the roof - and helps prevent ice from forming. When these systems are professionally installed, they are an effective way to prevent ice dams from occurring.