Flat Roof Snow Load

If your structure has a sloped or flat roof you still need to calculate the flat roof snow load.

Flat roof snow load.

Length of low roof ll. Snow is actually one of the easiest to design for and all. When discussing snow load with anyone it is crucial to have a clear understanding as to if the load is a ground or flat roof snow load. For ground snow loads greater than 20 pounds per square foot the roof load is equal to 70 of the product of the exposure thermal and importance factors the ground snow load and 20 pounds.

Asce 7 05 equation 7 1 assumes that the snow load results from multiple events. Horizontal distance from eave to ridge. If your roof is flat it is more likely to have snow load problems than if it is pitched. Flat roofs must be installed on a very specific mild slope so that the water can drain off properly and if the drains and scuppers aren t cleared regularly this increases the chance of a leak.

Certainly the weight of snow can add up but your home must support a variety of loads. A flat roof is no more or less likely to leak than a pitched roof it all comes down to the design and the competence with which it is installed. Length of roof upwind of the snow drift. After you obtain the roof slope factor from those sections in asce 7 10 the balanced design snow load for the sloped roof can easily be calculated using equation 7 4 1.

Ground snow load pg. Wind seismic building weight furniture occupants etc. The balanced snow. Figure 7 1 pages 84 85 and table 7 1 page 92.

The easiest way is to push a yardstick into the snow on the roof selecting an area that looks typical of the overall snow depth. Length of roof downwind of the snow drift. This is the snow load calculated in the previous section. First figure out how deep the snow is piled up there.

If you live in the us our snow load calculator compares the total weight on your roof with the permissible load calculated according to the standards issued by the american society of civil engineers regarding the minimum design loads for buildings and other structures asce7 16. If you have any concerns as you are determining your flat roof snow load consult with a structural engineer or roofing specialist. Flat roofs can t possibly support all the extra weight a totally valid concern but rest assured your architect and engineer have this in mind when designing the roof structure. Pf is flat roof snow load if as a consumer your concern is snowfall and you want to upgrade the ability of your building to carry it this is the value to increase.

In regions with relatively low snow load values the load from a single event may result in the peak loading. You need to use a snow load formula for flat roofs. Length of high roof lu. E 1 2 flat roof load p g 10 outline minimum roof snow load thermal factor unbalanced load drift load on adjacent roof parapet wall rtu drift sliding load on adjacent roof ponding faq s 11 unbalanced loads gable roof upper limit roof slope change lower limit roof slope simplify small eave to ridge distance change 12.