Steel Buildings in Europe

Part 8: Building Envelope 8 - 5 2.2 Built-up double skin cladding This common type of cladding consists of a metal liner, a layer of insulation material, a spacer system and an outer metal sheet, as illustrated in Figure 2.2. The span of such systems is limited by the spanning capability of the cladding sheets, which is typically in the order of 2 m to 2,5 m depending on the applied loading. Built-up cladding systems must, therefore, be supported by secondary steelwork (purlins or side rails). As the name suggests, these systems are built up from their constituent parts on site. 2 1 6 5 4 3 1 Weather sheet 2 Slope 3 Bar 4 Liner sheet 5 Bracket 6 Insulation Figure 2.2 Built-up roof cladding 2.2.1 Liner sheet The liner sheet serves several purposes:  It supports the thermal insulation  It provides an airtight layer  It provides restraint to the purlins. Liner sheets are usually manufactured from cold formed pre-coated steel or aluminium and possess a shallow trapezoidal profile (i.e. height 18 mm to 20 mm is illustrated in Figure 2.3). For steel liners, the sheet thickness is usually either 0,4 mm or 0,7 mm, while aluminium liner sheets are slightly thicker at 0,5 mm or 0,9 mm. The choice of liner will depend on the required spanning capability, the cladding installation method and the acoustic requirements of the cladding. Where required, the acoustic performance of the cladding, in particular its ability to absorb sound and minimise reverberation, may be enhanced by the use of a perforated liner sheet.