Once you have the ground snow load p g you can compute the flat roof snow load p f.
Flat roof snow load.
You can also find the load per square meter or square foot of roofing by opening the advanced mode.
Wind loads depend on wind speed and can vary as widely as the snow.
In colder regions the design snow load represents snow deposited by multiple snow events.
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.
For locations where 0 pg 20 psf all roofs with a slope w 50 with w in ft shall have a 5 psf rain on snow surcharge.
This may also be true in some more moderate climates as well.
Flat roof snow loads p f the snow load that is applied to our structure is not the ground snow load but in most cases the flat roof snow load.
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.
You need to use a snow load formula for flat roofs.
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.
If you want to calculate these values by hand use the following formulas.
If your roof is flat it is more likely to have snow load problems than if it is pitched.
Step 4 determine the flat roof snow load.
The design snow load represents the peak snow accumulation on a roof over the a winter season.
Flat roof snow load are determined by the following method.
The snow load pf on a roof with a slope equal to or less than 5 degrees 1 in ft 4 76 deg shall be calculated in lb ft2 kn m2 using the following formula.
First figure out how deep the snow is piled up there.
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.
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.
In our case let s assume that our structure has a flat roof roof slope 5.
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.
The flat roof snow load ρ f on a roof with a slope equal to or less than 5 degrees 0 09 rad 1 inch per foot 4 76 degrees shall be calculated in accordance with section 7 3 of asce 7.
Often changes of five or 10 pounds per square foot result in minimal differences in cost.
Other considerations for sloped roofs can be found throughout chapter 7 of asce 7 10.
0 7 x ce x ct x is x pg pf.
Pg is converted to pf by this formula.
