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Pole Barn Snow Load Calculator - Ground Snow, Roof Load & Truss Spacing Verification

Check if your pole barn trusses and posts can handle local snow loads per ASCE 7 standards

Free pole barn snow load calculator that converts ground snow load to roof snow load per ASCE 7 methodology and checks your truss spacing and post sizing against the calculated loads. Pole barns and post-frame buildings are the most common structure type for agricultural storage, equipment shelters, workshops, and livestock housing - and they are also the most common structure type to collapse under snow load. The reason is simple: most pole barn packages are sold with trusses designed for a specific snow load, but the buyer often has no idea what snow load their county actually requires. This calculator starts with your ground snow load (from ASCE 7 maps or local building department data), applies exposure, thermal, and importance factors to convert to balanced roof snow load, then checks that your truss spacing, post spacing, and connection details can handle the load. It also calculates unbalanced drift loads for buildings adjacent to taller structures, and sliding snow accumulation for lean-to additions - two conditions that cause disproportionate numbers of pole barn collapses. Enter your building dimensions, roof slope, exposure, occupancy, and truss/post specifications to get a pass/fail structural check with recommendations.

Pro Tip: The most dangerous snow load condition for a pole barn is not the deepest snowfall - it is the rain-on-snow event. A 12-inch snowpack at 5 lbs/cubic foot weighs about 5 PSF. Add an inch of rain that saturates the snow and it jumps to 10-12 PSF. Two rain-on-snow events without melting can double the load on a roof designed for 20 PSF. If your area gets rain-on-snow events, add 5 PSF to your design snow load as a rain surcharge.

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Pole Barn Snow Load Calculator
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How It Works

  1. Enter Ground Snow Load

    Input the ground snow load (Pg) for your location in PSF (pounds per square foot). Find this on the ASCE 7 map, from your county building department, or from local code. Common values: 20 PSF in the mid-South, 30-50 PSF in the Midwest, 50-100+ PSF in mountain regions.

  2. Describe Your Building

    Enter building width, length, and eave height. Select roof type (gable, single slope, or monitor) and enter roof slope in rise per 12 inches of run. Steeper roofs shed snow more easily and reduce the design load.

  3. Set Exposure and Importance

    Choose exposure category: windswept (reduced load), partially exposed (normal), or sheltered (increased load). Set importance factor based on use: normal storage or shop, occupied agricultural, or essential/high-value.

  4. Enter Structural Details

    Input truss spacing, post spacing, post size, and truss type. The calculator checks the tributary area per truss and per post against the calculated roof load.

  5. Review Load Analysis

    See balanced roof snow load, unbalanced drift loads (if applicable), total load per truss and per post, and pass/fail status. If your structure fails the check, get specific recommendations for reducing truss spacing, upgrading post size, or adding intermediate supports.

Built For

  • Farmers verifying that a pole barn kit is adequate for their county's snow load
  • Building inspectors checking pole barn snow load compliance
  • Insurance adjusters evaluating structural adequacy after a collapse
  • DIY builders designing a pole barn from scratch without an engineer
  • Property buyers in snow country assessing the structural soundness of existing pole barns

Frequently Asked Questions

Use the ground snow load for your county (from ASCE 7 or your local building department), then apply reduction factors for roof slope and exposure. A county with 40 PSF ground snow typically translates to 28-35 PSF balanced roof snow load depending on exposure and slope. Always check with your local building official - some jurisdictions require higher loads than ASCE 7 maps based on local experience.
Roof snow load (Pf) = 0.7 × Ce × Ct × Is × Pg. Where Ce is exposure factor (0.8-1.2), Ct is thermal factor (1.0 for heated, 1.1-1.3 for unheated), Is is importance factor (0.8-1.2), and Pg is ground snow load. For a typical unheated, partially exposed pole barn with normal importance: Pf = 0.7 × 1.0 × 1.1 × 1.0 × Pg = 0.77 × Pg.
Most pole barn collapses share one or more of these causes: (1) Trusses designed for a lower snow load than the site actually receives. (2) Drift loads from adjacent taller buildings or tree lines that were not accounted for. (3) Rain-on-snow events that double the load. (4) Deteriorated post embedment or truss connections. (5) Lean-to additions that accumulate sliding snow from the main roof. A 40-foot-wide pole barn with trusses at 4-foot spacing designed for 30 PSF carries 4,800 lbs per truss. Add an unplanned drift and it jumps to 7,000+ lbs.
Yes, for slopes greater than about 30 degrees (about 7/12 pitch). Below that, most codes do not give a slope reduction for cold roofs (unheated buildings). For heated buildings with slippery surfaces (metal roofing), a partial reduction begins at lower slopes. Most pole barns have 4/12 to 6/12 pitch, which gets little or no slope reduction for snow load.
Disclaimer: This calculator provides preliminary load estimates based on ASCE 7 methodology. It does not replace structural engineering analysis. Drift loads, sliding loads, and rain-on-snow surcharges require site-specific evaluation. All post-frame buildings should be designed by or reviewed by a licensed professional engineer, especially in areas with ground snow loads over 30 PSF.

Learn More

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Pole Barn Snow Load: What Your Building Code Requires

Ground snow load vs roof snow load, exposure and thermal factors, drift loads, unbalanced loads, IBC requirements, and when you need a structural engineer.

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