Required units are in KPa 20 ft of the roof, multiply the drift load by the factor: 20 s 20 where s is the spacing in feet. 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. Live load that includes both use and occupancy and snow load is conservative Reliability indices for the combination of dead load and snow load are smaller than other load combinations. The balanced snow load is applied everywhere where the roof structure is located. 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. Superpose the drift load on the base snow load. Combination of dead, wind and snow for steel: reliability index > 3, except where snow load dominates Check for loads due to snow sliding from an upper roof. See Section 7.9, ASCE 7. Right, 0.8 is the basic roof snow load factor. If your roof is 1,000 square feet, the total snow load is 15,000 pounds of snow. ROOF SNOW DRIFT SURCHARGE A N G L E Note a 15% increase in the allowable capacity of wood for loads that include snow, which is a short-term load Snow Loads 7/12 Cs 0.99 Slope 8/12 0.91 9/12 0.83 10/12 0.75 11/12 0.69 12/12 0.63 Note that roofs exceeding an angle of 30 degrees may reduce the ground snow load. Example 2: For a building with a fabric liner, R20 batt insulation, a heating system, and sprinklers, the total collateral load would be: 0.0125 kPa + 0.005 kPa + 0.075 kPa + 0.096 kPa + 0.15 kPa = 0.3385kPa; Ground Snow Load. But in accordance with NBCC (National Building Code of Canada), the Specified Snow Load for roof includes rain load as well. You can click on the map below to find the design ground snow load for that location. For dead loads, you are correct. OK for concrete but not for steel or timber. If your structure has a sloped or flat roof, you still need to calculate the flat roof snow load. Use our Utah Ground Snow Loads (2019) map to easily determine the historical ground snow load (Utah Code: Title 15A Chapter 3 Section 107) for any location in the State of Utah. F EXAMPLE CALCULATIONS Figure F-2. 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. Check for ice dams and icicle loads. Permanent Load Roof finishes Permanent Formwork F100 Gauge 1.2 350mm thick concrete slab (584+0.05x25) Total permanent load 0.30 kN/m 2 0.19 kN/m 2 7.09 kN/m 2 7.58 kN/m 2 Services General services Variable Load Imposed load on roof (UDL) Imposed load on roof (PL) Construction Load Snow Snow loading in accordance with BS EN 1991–1– 3 Done Calculate drift surcharge load: pd hd no As given in Sentence 4.1.7.1 S = Ss(Cb*Cw*Cs*Ca)+Sr Where, Ss is the ground snow load; Sr is the associated rain load. The BOCA code recognizes this and allows you to use the horizontal projection of the roof when calculating snow loads. SNOW LOADING Ground Snow Load (p g) p g = 20 psf Flat Roof Snow Load (p f) p f = 0.7C e C t Ip g p f = 0.7(1.0)(1.0)(1.0)(20) = 14 psf But not less than p f =(I)p g = 20 psf ASCE 7-05 Section 7.2 Figure 7-1 Section 7.3 Eq. See Section 7.4.5, ASCE 7. 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. Maximum uplift and lateral wind loads on roof. 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.