In summary, you should be familiar with the following codes prior to building purchase:
Roof Snow/ Wind Speed
0 lb. S/L/130 mph
0 lb. S/L/150 mph
4 lb. S/L/115 mph
20 lb. S/L115 mph
30 lb. S/L 115 mph
40 lb. S/L/115 mph
60 lb. S/L/115 mph
Typical snow loads in the United States can range from 4 to 60+ lbs per square foot depending on precipitation. Obviously, in warmer climates there are 0 lb minimum snow load requirements, whereas, in colder states where snow and ice hardly have a chance to thaw before the next storm, roof snow loads can be greater than 60 lbs per square foot. In addition, snow tends to drift and accumulate heavier in some spots than others, which is why snow loads are a factor in addition to the standard dead loads of a building.
Wind load is also determined by patterns of climate local to your building site. Wind speed codes range from 0 mph to over 160 mph winds.
Wind, unlike snow, will affect different portions of the building not limited to only the roof. The wind’s effects on your steel building structure will vary depending on your building design and how it sits on your property. During the software designing process, strength factors are determined by building height, the size and number of large framed openings, and even the location of those openings.
Also in relation to wind is the exposure of your building. Exposure B or C is site-specific. For example, in gusty areas, your local building department may require Exposure C if there are no windbreaks provided by your surroundings, such as trees or neighboring buildings. Wind exposure also affects how snow tends to drift and accumulate on your building structure.
While your metal building broker will ask you to confirm these codes per your local building department, the MBS (design and pricing software used by your broker) will recall default minimums when the representative enters your building site ZIP code. In many occasions, the local building department will ask you for higher than minimum requirements and dictate which building code year governs these specifics. For example, IBC 2015 or NCBC 2014 (International Building Code for year 2015, or North Carolina Building Code for year 2014, etc.)
In summary, contact your local building department to get specific governing year code, roof snow requirement, wind speed requirement, and the wind exposure requirement specific to your building site address and ZIP code.
If you want more education regarding other loads your building is designed for, please click to read “What’s Important About Steel Building Codes” to learn more.