How Much Snow Is Too Much On A Flat Roof

So a risky roof is flat or slightly.

How much snow is too much on a flat roof.

Low pitched and flat roofs are most susceptible to collapses. This is the one question that you need to answer. Of snow equals about 1 to 1 1 2 psf. It also helps if the roof is in a sheltered area.

The snow settles on it evenly rather than being blown into large drifts which can cause a roof to fail. If that sounds a little involved the national research council of canada estimates that 1 in. That means 12 inches of snow on a flat roof creates an additional r 12 of insulation that arrives at a time of year when you most need it. And whenever it snows the flat roof supports an additional insulating blanket.

Melting down a cubic foot of snow tells you how much water it holds and consequently how much the snow weighs. The weight of snow depends on how much water it contains. The r value or resistance to heat flow for snow is about r 1 per inch. As you know there is a big difference between a blizzard hitting your town and a dusting of snow.

These questions aren t quite so easy to answer because there are several variables. Fluffy fresh snow can weigh as little as three pounds per square foot compared with 21 pounds for wet heavy snow according to fema. Most roof designs can handle snow loads of 20 40 lbs per square foot. A cubic foot of water weighs about 62 pounds.

Roof collapse can happen to new and old buildings alike and can cause extensive damage to the building and contents. How much snow a roof can hold depends on the type of snow roofline and material among other considerations. A flat roof can be constructed to address the needs of the particular building regardless of location.