Have you ever driven by a house in the winter, its roof piled knee deep in snow and wondered, Just how much snow can a roof hold?
It’s not a bad question, because, according to insurance companies, roof collapse, is all too common – especially in the winter.
The problem is that most people not only have no idea how much weight their roof can hold, but also fail to estimate for the differing weights of ice, packed snow, and fresh snow.
So what is the answer? According to the Insurance Institute for Business and Home Safety (IIBHS) unless the roof structure is damaged or decayed, most residential roofs, regardless of the location of the house, should be able to support 20 lb. per square foot of snow before they become stressed.
But because snow and ice exert different weights on your roof and even packed snow is heavier than fresh snow, it’s important to know how to estimate how much pressure is being placed on your roof.
The IIBHS offers these guidelines:
Fresh snow: 10–12 inches of new snow is equal to one inch of water, or about 5 lb per square foot of roof space, so you could have up to 4 feet of new snow before the roof will become stressed.
Packed snow: 3–5 inches of old snow is equal to one inch of water, or about 5 lb per square foot of roof space, so anything more than 2 feet of old snow could be too much for your roof to handle.
Total accumulated weight: 2 feet of old snow and 2 feet of new snow could weigh as much as 60 lb per square foot of roof space, which is beyond the typical snow load capacity of most roofs.
Ice: 1 inch of ice equals 1 foot of fresh snow.
But just how quickly that snow will melt and runoff your roof depends on the outside temperature and the slope of your roof. A roof with a slope of 3 inches or more per 12 inches of horizontal distance will allow melting snow to run off more quickly that a flat roof.
So what should you do if your see the snow packing on your roof? The best choice is always to remove the snow as quickly, and safely as possible. While this can sometimes be done with the use of a snow rake and long extension arm, in some cases, it might also be time to call a professional licensed roofing contractor.
This article is brought to you by ASAP Roofing, a national leader in hail damage, roofing restoration, and exceptional customer service. ASAP has offices in Denver, Dallas, Indianapolis, and Salt Lake City.