Flat Roof Snow Load Formula

Determine the transient load of the roof.

Flat roof snow load formula.

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. Online snow load calculator for buildings with flat or low slope roofs for balanced snow drift and rain on snow surcharge loadings calculator asce 7 05 for structural engineers construction professionals and building planners. Snow weight length width cos pitch snow load the weight of snowis measured in kgor lbs. If the snow weighs 10 pounds per cubic foot and there are 1 5 feet on the roof each square foot of the roof is getting 15 pounds of pressure.

If your structure has a sloped or flat roof you still need to calculate the flat roof snow load. This is all of the natural stresses imposed upon a roof such as snow loads rain loads and wind loads. This is highly regional as weights of snow for example range from 10 to 300 pounds per square foot based on moisture and volume of the snow. Step 4 determine the flat roof snow load.

The equation for converting ground snow load p g to roof snow load p f is asce 7 05 equation 7 1. P g ground snow load l u length of upper roof l l length of lower roof h d height of snow drift w width of snow drift h b height of balanced snow load h c clear height from top of balanced snow load to closest point of adjacent roof h r height difference between roofs. Snow load thickness density the result snow load or the pressure exerted by the snow has the units of kn m or lbs ft. 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 roofs that are flat and with ground snow loads lower than 20 pounds per square foot the roof snow load is equal to 70 of the product of the exposure thermal and importance factors and the ground snow load. The sloped roof snow load p s shall be obtained by multiplying the flat roof snow load p f by the roof slope factor c s. The balanced snow load is applied everywhere where the roof structure is located. This equation includes factors that take into account exposure and building heat loss.

P s c s p f the thermal factor c t from table e 3 determines if a roof is cold or warm slippery surface values shall be used only where the roof s surface is unobstructed and sufficient space is available below the eaves to accept all the sliding snow.