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ASCE 7 Snow Load Determination

Updated Apr 3, 2026
Establishes snow load calculations based on ground snow load and roof configuration.

ASCE 7 Chapter 7 addresses snow loads, which are critical in cold climates. Ground snow load (pg) is the weight of snow on the ground during winter, obtained from snow load maps established by ASCE 7 and other sources. Ground snow loads vary from near zero in warm climates to 200+ pounds per square foot in heavy snow regions. Roof snow load depends on ground snow load, roof configuration (slope and exposure), importance factor, and thermal factors. Flat and low-slope roofs (under 15 degrees) typically have roof snow load equal to ground snow load or slightly less. Sloped roofs (over 15 degrees) have reduced snow load, with reduction factor increasing as slope increases. At 60 degrees slope, the snow load approaches zero as snow slides off. Exposure factor accounts for roof exposure to wind, with exposed areas shedding more snow and sheltered areas retaining more snow. Thermal factor accounts for heat loss from the building, with heavily insulated buildings (good thermal performance) having higher snow load because heat doesn't melt snow. Light-colored roofing has higher thermal factor than dark roofing. Unheated buildings or outdoor canopies have thermal factor of 1.2 or higher. Unbalanced loading creates asymmetric snow distribution across the roof, critical for beam design. Sliding snow from steeper portions of the roof can accumulate at lower portions, creating localized heavy loads. Rain-on-snow loading can increase weight and reduce drainage. Design snow load is typically the controlling load for roof framing in cold climates.

TAGS
asce7loadssnow
DETAILS
section
7
category
Snow Loads
code body
ASCE
code year
2022
SOURCES
🔗https://www.asce.org/publications-and-news/asce-7
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