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Guide / Structural safety

Carport snow load: why 250 kg/m² is no luxury in the Alpine region

Every winter, somewhere in Austria, carport roofs give way under wet snow — and almost every time it is a kit built to the limit. This article explains what snow load really means, how it is calculated in Austria and why we design all our carports for 250 kg/m² as a matter of course.

ALC Metalltechnik GmbH — Master metalworking business · As at 08/2026 · Updated on

In brief: Wet snow weighs up to 500 kg per cubic metre — half a metre of it loads every square metre of roof with around 200 kg. Many imported carports are rated for only 80 to 120 kg/m² and are therefore under-dimensioned for Carinthia, Upper Styria and other Alpine locations. Our carports carry a tested 250 kg/m² — on a double carport that is well over seven tonnes.

What does snow load actually mean?

Snow load describes the weight of snow cover that a roof must be able to carry per square metre. The standards state it in kilonewtons per square metre (kN/m²); for a mental picture the rule of thumb is enough: 1 kN/m² is roughly 100 kg per square metre. A rating of 250 kg/m² therefore means that 250 kg of snow may rest permanently on every square metre of roof without the structure reaching its limits.

What matters is not the depth of the snow but its density. Fresh powder is light, but snow settles, takes up water and becomes heavy:

Powder snow, freshapprox. 30–100 kg/m³
Old snow, settledapprox. 200–400 kg/m³
Wet snowapprox. 300–500 kg/m³
Iceapprox. 900 kg/m³

The most dangerous case is a warm front bringing rain onto an existing snow cover: the snow soaks it up like a sponge and the weight climbs within hours — precisely the weather pattern that southern Austria sees regularly in late winter.

A worked example: wet snow on a double carport

Take a roof of around 30 m² — roughly the size of a double carport — after a wet, heavy snowfall leaving 50 cm of wet snow at 400 kg/m³:

  • 0.5 m of snow × 400 kg/m³ = 200 kg on every square metre,
  • 200 kg/m² × 30 m² of roof = around six tonnes in total — the weight of four mid-size cars,
  • a roof designed for 100 kg/m² would be carrying twice its permitted load here — one designed for 250 kg/m² takes the situation with reserve to spare.

This is not a contrived worst case but a winter that Carinthian valley locations see every few years — think of the snow-pressure winters that have flattened entire forests in Upper Carinthia.

How Austria calculates snow load

The basis is Eurocode 1 (EN 1991-1-3) together with the Austrian application document ÖNORM B 1991-1-3. Austria used to work with coarse snow-load zones; since the 2022 edition the characteristic snow load is determined site by site, on the basis of a fine grid that can be consulted on the public natural-hazard platform HORA. Two neighbouring villages can therefore have noticeably different values, depending on altitude and exposure.

For Carinthia the site-specific values lie mostly in the range of about 1 to over 4 kN/m² — that is roughly 100 to over 400 kg/m², and considerably more in exposed mountain locations. Large parts of Styria, Upper Styria in particular, are also clearly above what a lowland kit will carry. (As at 08/2026, without guarantee — binding values come from the building authority or a structural engineer.)

Why imported carports fail in the Alpine region

Many cheap carport kits from DIY stores or online retailers are dimensioned for the Central European mass market — typically 80 to 120 kg/m². That is fine for the North German plain, but not for a side valley in Carinthia or a hillside near Leoben. The weak points are always the same:

  • Profiles and rafters that are too slender, designed to a price rather than to a load,
  • connections as predetermined breaking points: bolts and plug connectors fail before the profile does,
  • no reserve for snow drifts — against walls and in drifts a multiple of the average load builds up locally,
  • no site-specific structural design: the same kit is sold for Rostock and for Bad Kleinkirchheim alike.

The consequences range from permanent deformation to total collapse — and once damage has occurred, the question soon arises whether an obviously under-dimensioned structure was insured at all. Buying cheap here literally means buying twice. What a properly dimensioned carport actually costs is set out transparently in our cost guide.

What 250 kg/m² means with us in concrete terms

Our carports are made at our works in Völkermarkt from S235 JRH steel, hot-dip galvanised in Carinthia and designed for a snow load of 250 kg/m² — from the frame profile and the 85/280 trapezoidal sheet down to every bolted connection. That covers the site-specific requirements of most residential locations in Carinthia and Styria with reserve. For extreme mountain locations with higher standard values we plan individually — talk to us about a made-to-measure carport. That load also has to reach the ground, which is why the foundation guide treats snow load as the governing load case.

The difference is visible, too: see our references from all over Carinthia and Styria.

Please note: Standard values and calculation methods are presented here in simplified form (as at 08/2026, without guarantee). Binding for your project are the ÖNORM in its current edition and the information from the building authority or a structural engineer.

Frequently asked questions about snow load

How much snow load must a carport withstand in Austria?

That depends on the site: the governing snow load is determined location by location under ÖNORM B 1991-1-3, the Austrian annex to Eurocode 1. In the Alpine region, for instance in many Carinthian and Upper Styrian locations, values of 2 kN/m² (around 200 kg/m²) and well above are common. A carport built for 80 to 120 kg/m² is under-dimensioned there.

What does 250 kg/m² snow load mean in practice?

A roof of 30 m², roughly a double carport, carries 7.5 tonnes of snow at 250 kg/m² — about the weight of five mid-size cars parked on the roof. That reserve is needed because wet spring snow weighs several times as much as powder snow.

How heavy is snow really?

Fresh powder snow weighs about 30 to 100 kg per cubic metre, settled old snow 200 to 400 kg, wet snow 300 to 500 kg and ice around 900 kg. Half a metre of wet snow therefore puts 200 kg on every square metre of roof, and more still when rain falls on snow.

Is 100 kg/m² enough for a carport in Carinthia?

In most Carinthian locations, no. Many imported kit carports are rated for 80 to 120 kg/m², which suits lowland sites, not Alpine valleys with wet, heavy snow cover. Building under-dimensioned there risks deformation or collapse and, if damage occurs, an argument with the insurer.

Where can I find the snow load for my site?

Since ÖNORM B 1991-1-3:2022 Austria calculates snow loads site by site. The characteristic snow load can be looked up on the public HORA platform (hora.gv.at); binding figures come from a structural engineer or the building authority. We are happy to tell you how your postcode is classified.

Do I have to clear snow off my carport in winter?

A carport dimensioned to the standard must carry the snow load of its site without being cleared. In exceptional events, such as rain on a deep snow cover, checking is still sensible. A kit carport built to the limit, on the other hand, turns shovelling into a compulsory exercise.

Sources & legal basis

External sources retrieved on 23 Aug 2026. Laws each in the consolidated version of the Austrian Legal Information System (RIS), standards via Austrian Standards. Information without guarantee.

Further reading

Related guides

250 kg/m² snow load tested

Built for Alpine winters

Carports that can handle a Carinthian winter

Hot-dip galvanised steel from Völkermarkt, designed for 250 kg/m² — planned, manufactured and installed by a master metalworking business.

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