Civil Engineering Reference
In-Depth Information
• A sloping roof of not more than 30°, preferably less
• A roof covering made of high friction material, e.g. grass
• A snow barrier along the foot of the roof
• An unheated space under the roof, or very good roof insulation
• Windbreaks in front of the roof
• Reduced sun radiation on the roof, e.g. a single-sided pitched roof facing
north.
Many of these conditions have disadvantages. But the thermal insulation of
snow should certainly be seriously considered when designing in areas where
white winters are standard.
Snow is free, and is an efficient and environmentally-friendly insulating materi-
al. Zones with mild winters do not need 'snow-planning'; the same goes for sites
exposed to wind, but in many cases well-planned placing of snow drifts can pro-
vide excellent protection from wind. This can be done using special snow fenders
with an opening of approximately 50 per cent in the grid, and also with the help of
planted hedges and avenues. Snow will settle on the lee side in areas of turbulence.
Metal-based materials
The type of material dominant in this kind of work is metal sheeting. The sheet-
ing is used on exposed parts of the building's external skin, such as between the
roof and building parts that go through the roof such as chimneys, ventilation
units, vent stacks and roof lights, and on valley gutters and snow barriers at the
foot of the roof. Not all metal products are usable, as some corrode. Combinations
of different metals can create galvanic corrosion.
Stainless steel sheeting
This is usually an alloy of 17-19 per cent chrome and 8-11 per cent nickel. In
aggressive environments one uses an alloy of 16-18.5 per cent chrome, 10.5-14
per cent nickel and 2.5-3 per cent molybdenum. Stainless steel can be used in
combination with other metals. When corroding, chrome and nickel leak into the
groundwater and soil.
Galvanized steel sheeting
This needs about 275-350 g/m 2 zinc. The material should not be used with cop-
per. Gutters are often coated in plastic.
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