Steel Buildings in Europe

Part 2: Concept Design 2 - 45 7 CLADDING There are a number of generic types of cladding that may be used in single storey buildings, depending on the building use. These fall into four broad categories, which are described in the following sections. 7.1 Single-skin trapezoidal sheeting Single-skin sheeting is widely used in agricultural and industrial structures where no insulation is required. It can generally be used on roof slopes as low as 4° providing the laps and sealants are as recommended by the manufacturers for shallow slopes. The sheeting is fixed directly to the purlins and side rails, as illustrated in Figure 7.1 and provides positive restraint. In some cases, insulation is suspended directly beneath the sheeting. Figure 7.1 Single-skin trapezoidal sheeting 7.2 Double-skin system Double skin or built-up roof systems usually use a steel liner tray that is fastened to the purlins, followed by a spacing system (plastic ferrule and spacer or rail and bracket spacer), insulation and the outer profiled sheeting. Because the connection between the outer and inner sheets may not be sufficiently stiff, the liner tray and fixings must be chosen so that they alone will provide the required level of restraint to the purlins. This form of construction using plastic ferrules is shown in Figure 7.2. As insulation depths have increased, there has been a move towards “rail and bracket” solutions as they provide greater lateral restraint to the purlins. This system is illustrated in Figure 7.3. With adequate sealing of joints, the liner trays may be used to form an airtight boundary. Alternatively, an impermeable membrane on top of the liner tray should be provided.