Steel Buildings in Europe

Part 8: Building Envelope 8 - 22 should be obtained from the appropriate part of EN 1991 [9] , taking into account the building geometry and location as applicable. These individual actions should then be combined using the appropriate safety factors from EN 1990 [10] to obtain the load cases used in design. 3.8.1 Actions Permanent actions For most industrial and commercial applications of metal cladding technology, the only permanent action for which the roof cladding needs to be designed is its own self-weight, including the weight of the insulation. Typical weights of insulated panels and built-up cladding systems are given in Table 3.4. For information on specific cladding products, designers should consult the technical literature available from manufacturers or suppliers. For wall cladding, it is not normally necessary to consider permanent actions, since the self-weight acts in the plane of the cladding. However, where a rainscreen system is attached to the outer face of the cladding panel or assembly, it will be necessary to consider the impact of the rainscreen system weight when specifying the fasteners. Table 3.4 Typical cladding system weights Sheet thickness System Insulation Depth* Inner Outer Weight kN/m 2 Built-up Mineral wool 180 mm 0,4 mm 0,7 mm 0,16 Built-up Mineral wool 180 mm 0,7 mm 0,7 mm 0,20 Insulated Panels PIR 80 mm 0,4 mm 0,5 mm 0,12 * The depths chosen in Table 3.1 correspond to a U-value of 0,25 W/m 2 K for typical cladding systems using the insulation shown. Variable actions In addition to its self-weight, the roof cladding must also be designed for the following variable actions as specified in the appropriate parts of EN 1991:  Access for cleaning and maintenance  A uniformly distributed load due to snow over the complete roof area. The value of this load will depend on the building’s location  Asymmetric snow load and loading due to snow drifts  Wind pressure and suction. Care should be taken when ‘green’ roofs are specified, as they tend to be considerably heavier than traditional metal roofs and, in the case of roof gardens, must be designed for the presence of garden furniture and people. Wall cladding should be designed for wind loading according to EN 1991-1-4 [9] . Positive wind pressure and wind suction will need to be considered, with special attention paid to the areas of high wind suction close to the corners of the building. The wind suction design case is often governed by the resistance of the fasteners connecting the cladding panels or sheets to the supporting steelwork.