CHICAGO (WLS) -- With all the snow that has fallen in the past few weeks and several roof collapses reported across the Chicago area, you may be wondering how much snow your roof can hold.
The weight of snow varies by the water content of the snow. For example, fluffy snow has a snow to water ratio of 15 to 1. That means 15" of snow equals 1" of rain. The snow we have seen recently is even lighter than that, with a 30 to 1 ratio at times. The heavy wet snow we sometimes see has a ratio of 5 to 1.
But how much does that weigh?
With fluffy snow, a foot of snow weighs about 4 pounds per square foot. On a regular roof, that's about 6,240 pounds of weight on the roof. It's like putting a pickup truck on your roof.
For heavy, wet snow... a foot of snow on the roof is like having three pickups on the roof.
When you double that to 2 feet, those numbers go up. For fluffy snow, it is about two pickup trucks. For wet snow, it is about six pickup trucks on your roof.
Most roofs can support 2 feet of light fluffy snow and even snow with a ratio of 10 to 1. But if really heavy wet snow piles too high, it can cause serious damage to your roof.
Fortunately, the snow we've had recently has been the fluffy snow.