Snow Loads

Roof snow loads are influenced by elevation, general weather and moisture patterns, slope direction, exposure, roof configuration and wind direction and severity. Overestimation of snow loads can unnecessarily increase the cost of construction. Underestimation of snow loads can result in premature failure, and in some cases hazardous safety issues.

Most building codes in the United States reference the procedures found in ASCE 7 - Chapter 7 (Snow Loads). Roof snow loads are based on the historical records for ground snow loads for a given location, however the local building authority should always be consulted to determine the correct roof snow load to use for a given site and application.

The ground snow load map shown below was scanned from the ASCE 7-10 (Figure 7-1). Ground snow loads, pg, for the contiguous United States can generally be determined using this map. Ground snow loads for sites at elevations above the limits indicated and for all sites labeled "CS" require site-specific case studies and approval from the governing building authority. Ground snow loads for Alaska are given by Table 7.1 from the ASCE 7-10. Ground snow loads for Hawaii are zero, except in mountainous regions as determined by the authority having jurisdiction.

Please feel free to use our interactive ASCE Ground Snow Loads map for the contiguous United States.

Many states have additional snow load data and requirements for their jurisdictions. Please visit our State Snow Loads page for further details and interactive maps for each state.

If you need to gather ground snow load data programmatically, please consider our API Service.

Snow Load Calculations

Snow load calculations for most residential structures are usually performed using the following method:

As can be seen by the algorithm shown above the calculations required to obtain the balanced and unbalanced snow loads can become quite tedious and lengthy. Fortunately, all of this can be easily programmed thereby eliminating the need to manually calculate equations and referencing charts and tables from the ASCE Standard.

Please feel free to use our Roof Snow Load Calculator.

If you have any questions or concerns about specific snow loads please call us at 1-425-741-5555.

Copyright 2011-2015 Medeek Design Inc.