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.
Flat roof snow load equation.
The snow load p f on a roof with a slope equal to or less than 5 degrees 1 in ft 4 76 deg shall be calculated in lb ft 2 kn m 2 using the following formula.
The balanced snow load is applied everywhere where the roof structure is located.
P s c s p f.
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.
Snow load thickness density.
Step 4 determine the flat roof snow load.
The equation for converting ground snow load pg to roof snow load pf is asce 7 05 equation 7 1.
It also includes the importance factor seen in other load types which converts the data.
If your roof is 1 000 square feet the total snow load is 15 000 pounds of snow.
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.
To figure out the load on your roof take the depth of snow in feet and multiply it by the weight of a cubic foot of snow.
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.
This equation includes factors that take into account exposure and building heat loss.
Flat roof snow load are determined by the following method.
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.
Snow loads acting on a sloping surface shall be assumed to act on the horizontal projection of that surface.
The following are the equation for determining snow loaing on flat roofs.
If you want to calculate these values by hand use the following formulas.
This is all of the natural stresses imposed upon a roof such as snow loads rain loads and wind loads.
This rain on snow augmented design load applies only to the balanced load case and need not be used in combination with drift sliding unbalanced or partial loads.
You can also find the load per square meter or square foot of roofing by opening the advanced mode.
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.
If your structure has a sloped or flat roof you still need to calculate the flat roof snow load.
Once you know these values our snow load calculator automatically finds the total weight of snow on your roof.
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.
P f 0 7c e c t i p g.
