Flat Roof Snow Load

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.

Flat roof snow load.

You need to use a snow load formula for flat roofs. 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. 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. From eave to ridge w.

Minimum flat roof snow load values. 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. This is the snow load calculated in the previous section. Horizontal distance from eave to ridge.

Asce 7 05 equation 7 1 assumes that the snow load results from multiple events. As a result equation 7 1 which accounts for loss between events will result in a non conservative value. 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. Ground snow load pg.

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. 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. If you have any concerns as you are determining your flat roof snow load consult with a structural engineer or roofing specialist. Certainly the weight of snow can add up but your home must support a variety of loads.

First figure out how deep the snow is piled up there. Length of roof upwind of the snow drift. The balanced snow. Length of high roof lu.

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. Wind seismic building weight furniture occupants etc. 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. 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.

If your structure has a sloped or flat roof you still need to calculate the flat roof snow load. Length of low roof ll. Length of roof downwind of the snow drift. Figure 7 1 pages 84 85 and table 7 1 page 92.