Determining Exposure Factors for Calculating Flat Roof Snow Loads on Structures per ASCE 7-10

April 26, 2018 Abdul Siraj, P.E.

In this post, I will provide a brief overview of determining exposure factors, Ce, for calculating flat roof snow loads on structures per ASCE 7-10, Table 7-2. The exposure factors are based on the terrain category of the location of the structure and the exposure of the roof.

 

Exposure Factors for Terrain Category B

 

Fully Exposed Roof, Ce – 0.9

Partially Exposed Roof, Ce – 1.0

Sheltered, Ce – 1.2

 

Exposure Factors for Terrain Category C

 

Fully Exposed Roof, Ce – 0.9

Partially Exposed Roof, Ce – 1.0

Sheltered, Ce – 1.1

 

Exposure Factors for Terrain Category D

 

Fully Exposed Roof, Ce – 0.8

Partially Exposed Roof, Ce – 0.9

Sheltered, Ce – 1.0

 

Exposure Factors for Terrain Category Above Treeline in Windswept Mountainous Areas

 

Fully Exposed Roof, Ce – 0.7

Partially Exposed Roof, Ce – 0.8

Sheltered, Ce – N/A

 

Exposure Factors for Terrain Category in Alaska, in Areas Where Trees do not Exist Within a 2-mile Radius of the Site

 

Fully Exposed Roof, Ce – 0.7

Partially Exposed Roof, Ce – 0.8

Sheltered, Ce – N/A

 

ASCE 7-10, Table 7-2