Roof Slope Factor For Snow Load

All of the load cases required to fully design an actual structure are not provided by this calculator.

Roof slope factor for snow load.

Roof slope 0 degrees slope factor. S 1 0 1 0 8 1 0 1 1 0 1 1 8kpa s 1 8 kpa s 37 6 psf. P s sloped roof snow load in psf c s roof slope factor as determined by asce sec. 7 2b with a c s 1 0 p f flat roof snow load in psf.

If you want to calculate these values by hand use the following formulas. Slope 30 degrees. Residential roof with asphalt wood shingles or shakes would use fig. The balanced snow load is applied everywhere where the roof structure is located.

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. 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. 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. 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.

For the design of an actual structure a registered and licensed professional should be consulted as per irc 2012 sec. Calculate sloped roof snow load p s using the following equation. Once you know these values our snow load calculator automatically finds the total weight of snow on your roof. C s 1 uls.

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 load thickness density. You can also find the load per square meter or square foot of roofing by opening the advanced mode. This is the snow load calculated in the previous section.

The boca code recognizes this and allows you to use the horizontal projection of the roof when calculating snow loads. 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. P s c s p f where. If your structure has a sloped or flat roof you still need to calculate the flat roof snow load.

Boca also allows you to reduce the snow load for roofs with slopes greater than 30 degrees presumably because snow will slide or blow off steeply pitched roofs. For dead loads you are correct. 7 4 1 7 4 4 and asce figure 7 2 below.