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Snow load information

Snow
Frozen precipitation the weight and density of which depends on the temperature.


Snow load
Climatically-dependent changing influence on built structures. The snow load that presses down on a surface does not just depend on the depth of the snow. The type of snow and the type of the individual layers of snow play an important role. The higher the water content, the heavier the snow. The snow load also depends on the geographical location and the form of the built structure and generally acts as a surface load that is perpendicular to the ground.

For example, snow will slide faster from a steep roof than from a roof with a more gentle slope. The size and distribution of the snow load can also be influenced to a great extend by the wind conditions.


Snow load zones
Germany is divided into 5 regional zones (snow load zones). The intensity of the snow loads increases from zone 1 to zone 3.

Zone 1:       Rhine Valley and low-lying parts of the Rhineland, Parts of southern Germany
Zone 1a:     Munich and its environs, Augsburg and Regensburg
Zone 2:       Large parts of northern and eastern Germany
Zone 2a:     Black Forest, R.hn and the Sauerland
Zone 3*:     The Alps, the Bavarian Forest, the Thuringian Forest, the Erzgebirge, Harz and Pomerania

*In zone 3 some areas (e.g. Oberharz, higher parts of the Fichtelgebirge, Reit im Winkl, Obernach /Walchensee) may be subject to higher values than those indicated by the calculation formula. Details of the snow loads in these regions can be obtained from the relevant offices.


Standard EN 1991-1-3
Determination of snow loads in calculated values to determine structural safety. European standard EN 1991-1-3 is based on the new German dispensation. It applies up to altitudes of 1,500 m above sea level; higher altitudes are covered by special national addenda.


Calculation of snow load
The following parameters are included when calculating snow load. Snow load zone, altitude of the site, slop of roof, length from ridge to snow guard and the distinction between applications for "traffic safety" and "protection of lower lying structures" (structural engineering).

Calculation formula: sk . kS,α . lS = Fd,s

Sk = Snow load according to DIN EN 1991-1-3 per m2
(depending on the snow load zone and altitude of the site)

kS,α = Snow slippage factor on the roof surface
(depending on the slop of the roof and the application)

lS = Length from the ridge to the snow guard structure
(usually the rafter length, when several rows are used the determinate length to the snow guard system)

Fd,s = Snow load for the snow guard system per m


Traffic safety
The fundamental provision is based on the national building regulations. Article 32 of the Model Building Regulation requires that roofs along traffic thoroughfares and above entrances should be equipped with devices to prevent snow and ice from falling, if this is necessary for road safety purposes. Regional requirements, such as technical provisions, local regulations, etc. also apply.


DIN EN 516
Prefabricated roofing accessories - equipment for climbing on the roof – ladders, platforms and individual steps. This standard relates to permanently installed products that guide loads according to the construction of the sloped roof and that can be used to inspect, maintain and repair parts of the roof. It defines the key dimensions, materials corrosion protection, load-bearing capacity and test procedures. It does not apply to permanently installed roof ladders and fire escapes.