Snow, particularly heavy or wet varieties, can weigh about 21 pounds per cubic foot. This weight might not seem substantial, but it adds up quickly as snow accumulates on a rooftop. Before a roof collapses under the weight of snow, it exhibits warning signs that allow you to remedy the problem or evacuate the area.
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Buildings should have clean, straight lines without any visible signs of drooping or sagging. If you notice the roof sagging, from indoors or outdoors, the snow’s weight is too heavy for the building. In addition, any sprinkler heads that are pushed out, below the ceiling, might be indicators of damaged structural integrity. Utility pipes attached at the ceiling might also begin to bend or warp from the changing shape of the building’s structure. Remove snow from the roof immediately, before conditions worsen. Should any area crack or break, vacate the building immediately.
Doors and Windows
When a building’s structure is under high levels of stress from snow, you could notice strange occurrences with the doors and windows. If doors pop open on their own, or if they become difficult to open and close, the frame might be warping under the snow’s weight. Windows might become increasingly difficult to open and close as well. Take action to remove snow from the roof as soon as you notice these early warning signs. If doors and windows become nearly impossible to open or if windows begin breaking, vacate the building immediately.
Sounds of soft creaking and cracking are common in both new and old buildings and homes. However, it's a dangerous sign if you hear soft popping or creaking sounds more often, or only, during the presence of snow on your roof. When caused by a heavy snow load, these sounds indicate that the structure of the building is under stress. When you first begin to hear increased noises, take snow-removal action immediately; if they become loud or frequent, vacate the building.
Always remove snow from the roof, if possible. Snow rakes, available from most home-repair stores, allow you to remove snow from your roof with the aid of a long handle. If possible, use a snow rake to remove as much snow buildup as you can the moment, or before, any early warning signs appear. Remember, however, that metal snow rakes conduct electricity if they contact a power line -- so use caution when handling them. Also, avoid using ladders, as they collect ice and are dangerous to use in the winter. Call a snow-removal service if you cannot safely remove the snow by yourself. Only an able-bodied adult should shovel snow, as it is heavy and can cause injury.
Call the insurer of the building immediately if you notice any early warning signs of a roof collapse. If the signs become severe, ensure everyone is out of the building as soon as possible. Call emergency services if the roof is actively collapsing, or the fire department if you suspect an imminent collapse.