SNOW LOADS ON ROOFS DESIGN AND CALCULATIONS BASIC AND TUTORIALS

SNOW LOADS ON ROOFS DESIGN AND CALCULATIONS BASIC INFORMATION
What Are Snow Loads On Roofs Design And Calculations


Snow Loads Calculation
Determination of designing snow loads for roofs is often based on the maximum ground snow load in 50-year mean recurrence period (2% probability of being exceeded in any year).

This load or data for computing it from an extreme-value statistical analysis of weather records of snow on the ground may be obtained from the local building code or the National Weather Service.

Photo courtesy of Ask The Builder

Some building codes and ASCE 7-95 specify an equation that takes into account the consequences of a structural failure in view of the end use of the building to be constructed and the wind exposure of the roof:

pf = 0.7CeCtIpg (9.134)

where Ce wind exposure factor (range 0.8 to 1.3)
Ct thermal effects factor (range 1.0 to 1.2)
I importance factor for end use (range 0.8 to 1.2)
pf roof snow load, lb per ft2
pg ground snow load for 50-year recurrence period, lb per ft2

The “Low-Rise Building systems Manual,” Metal Building Manufacturers Association, Cleveland, Ohio, based on a modified form of ASCE 7, recommends that the design of roof snow load be determined from

pf = IsCpg(9.135)
where Is is an importance factor and C reflects the roof type.