Get Ready for Another Extreme Winter: Preventing Roof Collapse
The past two winters have brought record amounts of snowfall across the country, and forecasters are again calling for especially cold and snowy conditions this year. Avoid costly losses by getting prepared before freezing temperatures set in.
PREVENT ROOF COLLAPSE
Heavy accumulations of snow, ice and rain can lead to water damage and even roof collapse.
Evaluate the risk
Guidance for understanding how much snow is too much
1. Evaluate your risk of roof top snow/ice accumulation
A. Steep sloped roofs (slopes greater than 3-inches of slope in 12-inches of horizontal distance) and particularly the steeper ones that are typically found on houses in northern climates tend to shed melt water.
B. However, low slope and flat roofs over porches, lanais or parts of a home that are next to a taller section of the house can be at particular risk because of the tendency for snow and ice to accumulate in these areas, especially during periods windy weather.
2. Estimate how much weight your roof can support
A. Unless the roof structure is damaged or decayed, most residential roofs regardless of the location of the house should be able to support 20 pounds per square foot of snow before they get into trouble.
B. In some areas of New England or in some mountainous areas, the snow loads used in the design of homes may be considerably higher and the roofs may be able to resist a greater depth of snow.
C. If you live in an area known for lots of snow, you can probably check with your building department to find out if higher loads were used at the time your home was built.
3. Estimate how much the snow on your roof weighs using these guidelines from IBHS:
A. Fresh snow: 10-12 inches of new snow is equal to one inch of water, or about 5 lbs per square foot of roof space, so you could have up to 4 feet of new snow before you need to worry.
B. Packed snow: 3-5 inches of old snow is equal to one inch of water, or about 5 lbs per square foot of roof space, so anything more than 2-feet of old snow could be dangerous.
C. The total accumulated weight of two feet of old snow and two feet of new snow could be as high as 60 lbs per square foot of roof space, which is beyond the typical snow load capacity of most roofs.
D. If there’s ice, it’s much heavier, with one inch equaling about a foot of fresh snow.
Snow removal may be necessary to avoid roof collapse.
1. If you are in the “danger zone” according to chart above or if the loads you estimate based on the thickness of the various types of snow and ice exceed 20-25 psf, you should consider removing snow from your roof.
2 .For safe removal that won’t endanger you or damage your roof, use a snow rake with a long extension arm that will allow you to remove the snow while standing on the ground or hire a snow removal contractor.
Source: EMC Insurance Company & The Insurance Institute for Business & Home Safety