A metal carport’s snow rating only holds when its listed assumptions match your site, anchorage, and locally adopted building code.
A carport rated at 35 PSF can still fail under a snowpack that reaches half that number on paper, because the number printed on a retail listing is a starting point for a conversation with your building department, not a permit. That gap between a marketing spec and an engineered design load is where most winter carport collapses originate.
Manufacturers rate metal carports by the pounds per square foot (PSF) of load the structure is engineered to carry. Those figures come wrapped in assumptions — standalone installation, no enclosure panels, secure anchoring to local code, an unoccupied structure — and when any assumption breaks, the rating stops applying to your carport. Below is what PSF actually measures, why a 35-PSF sticker rarely tells the whole story, and how to verify a carport will survive your specific snowpack.
What A Snow Load Rating In PSF Actually Means
A PSF rating describes pounds of uniformly distributed load per square foot of roof area, not the depth of snow the carport can hold. A nominal 35-PSF load over a 200-square-foot roof equals 7,000 pounds of total load spread across the structure — but structural adequacy still depends on the framing system, load path, roof geometry, connections, foundations, and load combinations.
Treat the rating as the entry point to an engineering question, not the answer. Two carports can both say “35 PSF” while carrying completely different framing, gauge steel, and anchor schedules. The number compresses the structural math into a single figure, and that compression is where the trouble hides.
The critical distinction most shoppers miss: ground snow load and roof snow load are not interchangeable. A manufacturer may advertise a ground-load figure while your building official requires a calculated roof design load after code reductions or increases. Snow also accumulates unevenly — sliding snow, drifts against taller adjacent structures, and roof obstructions routinely produce localized forces well above a uniform rating.
Why A 35-PSF Sticker Rarely Tells The Whole Story
Documented product examples all carry the same quiet caveats. The Arrow 10-ft × 20-ft × 7-ft charcoal carport lists a 100-MPH wind rating and a snow/ground-load rating up to 35 PSF — calculated under ASCE 7-05 combined snow-and-wind provisions, for a standalone unit without an enclosure kit, securely anchored to local codes, in an unoccupied structure.
| Listing Claim | What It Really Assumes | What Breaks It |
|---|---|---|
| 35 PSF snow/ground load | Uniform load, combined snow and wind | Drifts, sliding snow, unbalanced loads |
| 100-MPH wind rating | Standalone, exposed-site exposure | Adjacent walls changing wind pressure |
| Secure anchorage to code | Anchors match engineered spacing | Loose anchors, unverified soil or slab |
| Unoccupied structure | No stored goods, no extra dead load | Storing heavy items inside |
| No enclosure kit | Open sides, no added wall loads | Adding panels, doors, or solar gear |
| ASCE 7-05 calculation basis | Older loading standard edition | Local code now citing ASCE 7-22 |
The Arrow 12-ft × 24-ft eggshell carport lists the same 35-PSF capacity with the identical caveats, and a second Arrow 12-ft × 24-ft unit repeats the 100-MPH wind and 35-PSF snow/ground-load combination. The VEIKOUS metal carport uses a 29-gauge steel roof and 2-inch × 2-inch 15-gauge steel tubing, also with a 35-PSF snow-load capacity and a 100-MPH wind rating — and its listing specifies a level surface, 10-ft frame width, 15-ft roof length, 7.5-ft frame height, and a 360-lb product weight. Every one of those figures comes with the same entrance requirement: your site, not the catalog, decides the design load.
How To Verify Whether A Carport Meets Your Local Code
The legally required design load comes from your locally adopted building code, not from a retailer’s spec sheet. The current ASCE loading standard is ASCE/SEI 7-22, adopted by reference into the International Building Code and International Residential Code, with revised ground-snow-load provisions based on updated snow data and reliability targets. Ratings supplied by a retailer or manufacturer are not a substitute for that code, its permit requirements, or a site-specific structural design.
State rules can set a floor. Montana, for example, states a minimum design roof snow load of 30 PSF after permitted reductions under Montana law, and directs users to obtain applicable loads from the building official or the ASCE 7 Hazard Tool depending on jurisdiction, per the Snow Load Information page from the Montana Department of Labor and Industry. And structural evaluation can impose its own minimum: a current ICC Evaluation Service report covering certain patio-cover and carport systems states that carports and commercial structures require a minimum live load of 20 PSF — 10 PSF for patio covers — and limits applicability where flat-roof snow load exceeds 30 PSF unless specified engineering provisions apply, while excluding certain sliding-snow effects.
To verify your carport, work through these gates in order:
- Identify the exact model, dimensions, roof style, enclosure configuration, anchoring method, and manufacturer rating.
- Get the required ground and roof snow loads for your address from the local building department or the applicable ASCE 7 data source.
- Confirm whether the product rating is ground snow, roof snow, or a combined snow-and-wind value.
- Check every assumption: standalone versus enclosed, occupied versus unoccupied, level surface, foundation type, anchor spacing, and permitted wind exposure.
- Compare your required local design load against the full manufacturer engineering package — not a retail listing.
- Pull permits and engineered drawings where your jurisdiction requires them.
On Windows, Mac, or a phone, this all comes down to phone calls and paperwork, not software. If you want a shorter starting list, our tested roundup of carports rated for heavy snow narrows the field before you start calling building departments.
One safety rule outranks every other: remove accumulated snow when the manufacturer or engineer directs it, and never climb onto or shovel a carport that may already be structurally compromised. Overloaded roofs can fail suddenly and without warning.
Does A 35-PSF Rating Mean The Carport Is Safe In My Snow Zone?
Not automatically. A 35-PSF listing may reflect a ground-load figure calculated under older ASCE 7-05 provisions for a standalone, unoccupied structure, while your jurisdiction could require a different roof design load under ASCE 7-22. Compare the required local design load against the manufacturer’s full engineering package before assuming the rating covers your location.
Can I Add An Enclosure Kit Or Storage To A Rated Carport?
Only after verifying the structure remains adequate for the added loads. Manufacturers like Arrow explicitly tie snow and wind ratings to standalone units without an enclosure kit. Adding wall panels, doors, stored goods, or rooftop solar equipment changes the load path and may void the engineering basis behind the original 35-PSF figure. Get confirmation before modifying.
What Happens If I Anchor A Carport Differently Than The Engineered Design?
The rating no longer applies. Every documented 35-PSF and 100-MPH figure assumes secure anchorage according to local codes, matching the engineered anchor spacing and foundation type. Loose anchors, an unverified slab, or a different anchor pattern can compromise the load path and let wind uplift or snow load exceed what the structure was designed to resist.
Sources
- American Society of Civil Engineers. “ASCE/SEI 7-22: Minimum Design Loads and Associated Criteria for Buildings and Other Structures” Current ASCE loading standard adopted by reference into the IBC and IRC.
- Montana Department of Labor and Industry. “Snow Load Information” States the 30-PSF minimum design roof snow load floor under Montana law.
- ICC Evaluation Service. “ESR-1953P Evaluation Report” Sets 20-PSF minimum live load for carports and limits applicability above 30-PSF flat-roof snow load.