The Dangers of Rain After Heavy Snow on a Roof

Formation of Ice Dams

• An ice dam is a ridge of ice and hardened snow that can form along the edge of a roof after a heavy snowfall. After snow falls, the heat from a roof can cause the snow to melt and flow down toward the gutters, but as water reaches the gutters, it may freeze in the absence of the heat given off by the roof. Once an ice dam forms, water cannot flow down into the gutters, and it may settle in pools behind the dam. If rain happens to fall after a heavy snowfall, it may add to the accumulation of water behind ice dams.

Water Damage

• One of the primary dangers of heavy snowfall and water accumulation behind ice dams is the possibility of water damage. Water that sits on the roof too long without proper drainage may start to leak into the roof and into the home. This can lead to wet insulation, cracks in ceilings and rotting wood. Water damage that goes unchecked can also result in the formation of mold and mildew. Molds and mildew may stain walls affected by water damage and introduce irritants into the air.

Exterior Damage

• Heavy snow, ice formations and trapped rain can also lead to exterior damage. Thick ice dams and trapped water can be very heavy, which can potentially cause gutters or roofs to fail and collapse.

Falling Ice

• Falling ice is another hazard that can be caused by heavy snow and rain. If ice dams form, they will eventually melt during the spring. Melting may cause large quantities of ice and snow to fall from roofs suddenly, which presents a serious safety hazard to anyone below the roof. Energy Star recommends that homeowners avoid standing on the ground and attempting to chip away at ice dams, as it can cause them to dislodge and fall, which could result in injury.

Considerations

• The dangers of heavy snow and rainfall can be mitigated by taking steps to eliminate the formation of ice dams. Cleaning gutters before the weather turns cold and removing snow from roofs immediately after heavy snowfalls can help prevent the formation of ice dams.