In this post, I will provide a brief overview of the importance factors by risk category of buildings and other structures for snow, ice, and earthquake loads that are specified in ASCE 7-10, Section 1.5.

## Risk Category I

Snow Importance Factor, Is = 0.80

Ice Importance Factor – Thickness, Ii = 0.80

Ice Importance Factor – Wind, Iw = 1.00

Seismic Importance Factor, Ie = 0.80

## Risk Category II

Snow Importance Factor, Is = 1.00

Ice Importance Factor – Thickness, Ii = 1.00

Ice Importance Factor – Wind, Iw = 1.00

Seismic Importance Factor, Ie = 1.00

## Risk Category III

Snow Importance Factor, Is = 1.10

Ice Importance Factor – Thickness, Ii = 1.25

Ice Importance Factor – Wind, Iw = 1.00

Seismic Importance Factor, Ie = 1.25

## Risk Category IV

Snow Importance Factor, Is = 1.20

Ice Importance Factor – Thickness, Ii = 1.25

Ice Importance Factor – Wind, Iw = 1.00

Seismic Importance Factor, Ie = 1.50