Snow load is one of the most consequential structural inputs for any building in Minnesota. The state's climate produces heavy, persistent snowpack—especially in the north and northeast—and a pole barn that is not engineered to handle the regional ground snow load is a liability from day one. Understanding how snow loads are determined, how they vary across the state, and how engineers translate them into a structural design helps you ask the right questions when planning your project.
What Is Ground Snow Load?
Ground snow load (Pg) is the weight of snow on the ground, expressed in pounds per square foot (psf). It represents the maximum snow accumulation that a region can statistically expect—historically measured at a 50-year mean recurrence interval—and serves as the starting point for all structural snow load calculations. The reference standard is ASCE 7, Minimum Design Loads and Associated Criteria for Buildings and Other Structures, published by the American Society of Civil Engineers. Minnesota has adopted and amended the snow load requirements of this standard within its own state building code.
Ground snow load is not the same as roof snow load—the two numbers differ because of how roofs shed snow, how exposed they are to wind, and whether the building is heated or unheated. The relationship between the two is defined by engineering formulas that account for these variables.
Minnesota's Two Snow Load Zones
The Minnesota State Building Code establishes two statewide ground snow load values, published in a snow load map maintained by the Department of Labor and Industry. The values are straightforward: most of northern and central Minnesota carries a 60 psf ground snow load, while southern Minnesota counties are designated at 50 psf. These are the design values that engineers use as the basis for structural calculations—they are minimums that the code requires buildings to be designed to withstand.
60 psf Zone: Northern and Central Minnesota
The Minnesota State Building Code specifies a 60 psf ground snow load for the following counties: Aitkin, Becker, Beltrami, Carlton, Cass, Clearwater, Cook, Crow Wing, Hubbard, Itasca, Kanabec, Kittson, Koochiching, Lake, Lake of the Woods, Mahnomen, Marshall, Mille Lacs, Morrison, Norman, Otter Tail, Pennington, Pine, Polk, Red Lake, Roseau, St. Louis, Todd, and Wadena. This band covers much of the state from the northwest border counties down through the north-central lake country and into the east-central counties where Sherman Buildings works most frequently. If you are building in Kanabec, Pine, Crow Wing, or St. Louis County, your project is designed to the 60 psf standard.
50 psf Zone: Southern Minnesota
All counties not listed in the 60 psf zone default to 50 psf. These are primarily the southern Minnesota agricultural counties—the Twin Cities metro and surrounding region, and the southern plains. A 50 psf design load is still substantial: that is roughly the equivalent of five inches of wet, dense snow per square foot across the entire roof surface. Chisago County, for example—just south of Pine County—confirms a 50 psf ground load requirement for pole buildings permitted in that county.
From Ground Snow Load to Roof Design Load
Ground snow load is the raw input. The structural engineer converts it to a flat-roof snow load (Pf) using the formula from the Minnesota State Building Code and ASCE 7:
Pf = 0.7 × Ce × Ct × Pg. At its most basic, the DLI's snow load guide illustrates the simplified residential code version as 0.7 × Pg = Pf. For the 60 psf zone: 0.7 × 60 = 42 psf roof snow load. For the 50 psf zone: 0.7 × 50 = 35 psf roof snow load. These are baseline values before adjustments for exposure and thermal conditions.
The variables Ce and Ct account for exposure and thermal conditions. Ce (exposure factor) adjusts for how open or sheltered the site is—a building in a wind-swept open field sheds snow more easily than one surrounded by trees. Ct (thermal factor) adjusts for building temperature: unheated buildings like most pole barns carry a Ct of 1.2, which increases the design roof load compared to a heated structure because snow does not melt off the roof from interior heat. This is an important nuance: an unheated machine shed in northern Minnesota ends up with a higher engineered roof load than a heated shop of the same size and location.
Drift Loads and Unbalanced Snow: The Real-World Complication
The uniform design load is only part of the picture. Wind causes snow to drift and accumulate unevenly across a roof surface—a phenomenon the code addresses specifically because drifts create concentrated loads far higher than the uniform design value.
Common drift scenarios for pole barns include:
- Leeward drifts at the base of a tall wall or at a step in roof height, where blowing snow piles up against the vertical surface.
- Lean-to or addition roofs that catch drift from the adjacent higher roof.
- Unbalanced loads on gabled roofs, where wind sweeps one side nearly clear while the other accumulates.
- Sliding snow from upper roof sections onto lower adjoining roofs.
ASCE 7 Chapter 7 addresses drift loads directly, and a properly engineered post-frame building accounts for them in truss and purlin design. Buildings with multiple sections, lean-tos, or varying eave heights require particular attention to drift load analysis at the transition points.
Why Trusses Are Engineered Per Site
Wood trusses are engineered components. The Minnesota State Building Code requires that they be designed by a Minnesota-licensed engineer to accepted engineering standards. This is not a formality—it reflects the fact that every truss must be sized to handle the specific combination of snow load, roof pitch, truss spacing, span, and building use that applies at your location.
A truss designed for a 42 psf roof snow load in the 60 psf zone will have different member sizing, plate specifications, and web configurations than one designed for 35 psf in the south. Truss spacing also matters: in heavier snow zones, trusses may be spaced more closely, or purlins may need to be sized larger to span between trusses without overstressing under accumulated snow. All of this is site-specific—a one-size-fits-all approach is not code-compliant.
Sherman Buildings provides engineered truss packages for every building. The truss manufacturer's design drawings—including load assumptions—are part of the permit package submitted to the local jurisdiction.
Snow Load, Frost Depth, and Post Embedment
Snow load engineering does not occur in isolation from other site factors. In Minnesota, frost depths reach 42 to 60 inches or more in many areas—the same northern counties with higher snow loads also have the deepest frost penetration. Post embedment depth must account for both the frost line (to prevent heaving) and the structural loads (to prevent post rotation or pullout under combined snow and wind loads). The local building department confirms required footing depths based on site conditions or county default values.
The footing must support all loads simultaneously: dead load (the weight of the building materials), live load, snow load, and wind load. A properly engineered post-frame building in northern Minnesota integrates all of these into a continuous load path from the roof ridge down to the bottom of the embedded post.
Why This Matters for Your Building
The practical consequence of snow load engineering is that a pole barn built in Kanabec County (60 psf zone) is a structurally different building than one built in Nicollet County (50 psf zone), even if they look identical from the outside. The trusses, purlin sizing, post dimensions, and footing design will reflect the specific load requirements of the site.
When you request a quote from Sherman Buildings, we ask for your project location specifically because the structural design—and therefore the materials and engineering—is calibrated to the snow load, wind exposure, frost depth, and soil conditions at your site. A building package designed for one location cannot simply be transplanted to another without engineering review.
If you are comparing bids from multiple contractors, confirm that each quote is based on the correct design ground snow load for your county and that the truss design documents reflect it. A building designed to a lower-than-required snow load may pass a cursory inspection but will be undersized for Minnesota winters.
Frequently Asked Questions
What is the ground snow load for Kanabec County, MN?
Kanabec County is in the 60 psf ground snow load zone under the Minnesota State Building Code. The baseline flat-roof design load (using the 0.7 factor) is 42 psf before thermal and exposure adjustments.
Does roof pitch affect snow load on a pole barn?
Yes. Steeper roofs shed snow more readily than low-slope roofs, and the engineering accounts for this through slope reduction factors in ASCE 7. However, steeper pitches also increase wind uplift forces, so the roof pitch is a balance of multiple structural considerations—not simply a snow-shedding choice.
Are unheated pole barns designed differently for snow load than heated buildings?
Yes. Unheated buildings use a thermal factor (Ct) of 1.2 in ASCE 7 calculations, which results in a higher design roof snow load compared to a heated structure. This reflects the fact that interior heat does not contribute to melting snow off the roof of an uninsulated, unheated building.
