Snow Weight On Flat Roof

To calculate the weight of snow on a roof use the first two sections of our snow load calculator.

Snow weight on flat roof.

Ice and snow will typically accumulate more quickly on low slope and flat roofs. 3 5 inches of old snow is equal to one inch of water or about 5 lbs. Damages snow causes to flat roofs ponding bowing. House roofs should support 20 lbs square foot of snow before they become stressed.

Since snow falls at slow steady speeds large quantities of snow can fall on the roof resulting in bowing. Contact your local building code department to determine the snow load requirements for your area. If your roof is pitched enter the length and width of the flat area covered by the roof. As snow falls it can accumulate on your flat roof putting unnecessary weight on the structure.

Local building codes dictate the snow load required for residential roofs. Two feet of snow on a roof with a footprint of say 28 40 feet could weigh 45 000 pounds. Two feet of old snow and two feet of new snow could weigh as much as 60 lbs. That s more than 22 tons.

This down bearing pressure can cause the roof to bow and result in ponding under the roof structure. Length and width of your roof. What s the weight of snow on a roof. Per square foot of roof space so anything more than 2 feet of snow could be too much for your roof to handle.

The roof deck collects the snow load and transfers the weight to the rafters. Flat roofs may be especially vulnerable to roof collapse depending on its engineered design load. You can enter these values in any units you d like including meters and feet. Snow won t slide off.

You need to supply the following information. For any rafter the portion of the roof deck that transfers this load is the tributary area.