Greenhouse Wind and Snow Load Claims: What Evidence Buyers Should Ask For

A greenhouse product page says “wind resistant to 90 mph” or “snow load capacity: 1.4 kN/m².” The buyer is deciding whether to repeat that claim in their own retail listing. Should they?

The answer depends on what evidence supports the claim. A load rating without supporting documentation is a marketing phrase, not a specification. If a customer’s greenhouse is damaged in a wind or snow event below the claimed rating, and the buyer has repeated the claim without verification, the liability sits with the retailer.

Why a Single Load Number Is Not a Specification

“Wind resistant to 90 mph” or “snow load 1.4 kN/m²” sounds specific, but leaves out every variable that determines whether a greenhouse will actually survive:

• Greenhouse size and geometry — A 6 m² greenhouse and a 17 m² greenhouse experience different wind loads even at the same wind speed
• Door and vent position — An open door or vent during a wind event creates internal pressure that can lift panels
• Anchoring method — A greenhouse anchored to a concrete foundation survives different wind loads than one sitting on paving stones with no anchors
• Test method — Was the rating derived from a computational calculation, a physical test, or a manufacturer’s estimate?
• Definition of “resistance” — Does it mean no damage? No collapse? Or simply the maximum load considered in design?

Without these details, the claim is not verifiable.

EN 13031-1 as a Reference Framework

The European standard EN 13031-1, published in 2001, is titled “Commercial production greenhouses — Design and construction.” It provides a framework for greenhouse structural design including wind-load and snow-load requirements. While its scope is commercial production greenhouses, its methodology is relevant to home garden greenhouses as a reference framework — it demonstrates how load claims should be substantiated.

The standard considers wind zone, exposure category, structure geometry, and component/cladding loads. It also uses national annexes that specify different snow-load values for different geographic regions.

However, referencing EN 13031-1 as a design framework is not the same as claiming a specific greenhouse has been certified to that standard. Home garden greenhouses are typically not certified to EN 13031-1. Buyers should treat it as a reference for understanding what a proper load claim should include, not as evidence that their product meets the standard.

Three Levels of Evidence

Engineering calculations — A structural engineer calculates wind/snow loads on the frame, profiles, panels, and connections, referencing a design standard. This is the most common method for greenhouse manufacturers. The calculation should specify design wind speed, exposure category, door position, and anchoring assumptions.

Physical testing — A prototype is tested in a wind tunnel or with wind/snow load generators. More expensive and less common for home garden greenhouses, but provides direct evidence specific to the exact model tested.

Seller claims — The manufacturer states a number based on experience or comparison. This is the least reliable form of evidence. It may reflect real-world experience but does not constitute a tested or calculated specification.

For home garden greenhouses, engineering calculations are the most realistic level of evidence to expect.

What to Ask the Supplier

1. What is the source of the claim? Calculation, test, or estimate? Who performed it, and when?
2. What design standard was used? If the calculation references EN 13031-1 or a national building code, the methodology is traceable.
3. What conditions were assumed? Wind speed, exposure category, door/vent position, anchoring method.
4. Does the claim apply to this specific model and size? A claim for a 6 m² greenhouse does not automatically apply to a 17 m² greenhouse from the same product line.
5. Is there documentation? A calculation summary, test report, or technical note — not just a number on a product page.

Snow Load: Additional Variables

Snow load is not the same as placing a static weight on the roof. It depends on snow type (dry snow typically 100–200 kg/m³; wet snow can weigh 400–600 kg/m³), snow distribution (wind causes uneven drifts), roof geometry (steep roofs shed snow; flat roofs hold it), and dynamic effects (ice dams, sliding snow impact).

A snow-load number without knowing the corresponding snow depth, type, roof geometry, and whether it accounts for drift accumulation is not directly actionable.

The structural variables that determine actual snow resistance include roof span, profile spacing, panel support, foundation anchoring, and roof bracing. Two greenhouses with the same “1.4 kN/m²” claim may have different actual snow-resistance capabilities because of different structural configurations.

Safe Ways to Write Retail Claims When Evidence Is Limited

If the supplier cannot provide engineering calculations or test reports:

• Describe the design features that contribute to wind/snow resistance rather than claiming a specific number. For example: “The greenhouse frame includes roof and wall cross-bracing, a galvanized steel base kit with ground anchors, and a steep-pitch roof design for snow shedding.”
• State the design intent without claiming a tested rating. “Designed for typical home garden conditions, including exposed and coastal gardens.”
• Include installation requirements. “Wind resistance depends on proper anchoring. Install on a level foundation using the included base kit and ground anchors.”
• Do not repeat a specific wind speed or kN/m² number in retail listings unless you can substantiate it with documentation.
• For snow regions, include a winter-use advisory. “For regions with heavy snowfall, we recommend clearing accumulated snow from the greenhouse roof to prevent excessive loading.”

A load number is not a product feature. It is a structural performance claim that requires product-specific evidence. Without that evidence, describe what the greenhouse is designed to do — do not claim a number that cannot be substantiated.