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Feb 19, 2015 4:08 PM

Test with PVC pipe, tape measure shows how heavy snow is on roof


Roof collapses are becoming more common as winter continues to strike New Hampshire hard.

With this latest storm, some parts of our region are seeing six inches or more fresh snow. That means more weight on some roofs that are already stressed.

Just two feet of snow on a 1000 sq. ft. roof could, conservatively speaking, equal 10,000 lbs. of weight. That's equivalent to 10 moose, and that's if it's light snow weighing just 5 lbs. per cubic foot. Snow can easily weigh up to four times more - 20 or more pounds per cubic foot depending on its density.

Here's how you can test to see how much the snow on your roof weighs. Use a piece of PVC pipe with a cap, push it down to the base of the snow, then turn it upright and let the captured snow melt.

Each inch of water equals roughly 5.2 pounds per sq. ft. Say you have 8 inches of water in the PVC pipe. That would equals 41 lbs. per sq. ft.

All roofs and how much weight they can withstand are different, but roofers say a good rule of thumb is two feet or more of snow and it needs to come off.

Roofs are designed to have the snow load spread out equally. Sometimes wind causes drifts that can imbalance the load on the roof. That can make it more susceptible to collapse.


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