Ground snow load and roof snow load are not the same number. Here is a plain-language breakdown of PSF and why it matters for snow retention planning.
PSF, or pounds per square foot, is the unit used to describe how much weight a given amount of accumulated snow places on a roof. It shows up constantly in snow retention planning, but it is often misunderstood, or confused with a different number entirely.
Ground Snow Load vs. Roof Snow Load
Ground snow load is a baseline figure published for a given location, based on historical weather data. Roof snow load is a separate, adjusted figure that accounts for roof pitch, exposure, thermal factors, and local building code requirements. The two numbers are related, but roof snow load is almost always lower than ground snow load, and it is the number that actually matters for planning a snow retention system.
Why This Number Drives Layout Decisions
Higher roof snow load generally means more retention capacity is needed across the roof, which affects row spacing and component count. Getting this number wrong in either direction can mean an underbuilt system or unnecessary added cost.
Where to Get an Accurate Number
Local building departments and project engineers are the most reliable source for a roof snow load figure specific to a project address. Because code requirements and local conditions vary widely, project-specific review may be required, particularly for larger commercial roofs or unusual roof geometries.
Once a roof snow load figure is confirmed, the ArcticAnchor™ calculator can help translate that number into an estimated system layout for standing seam, exposed fastener, or tile roof applications.
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