Steel Buildings in Europe

Part 8: Building Envelope 8 - 9 on a pitched roof) are transferred from the external sheet through the two adhesive bonds and the layer of insulation to the internal sheet and the supporting structure. Polyisocyanurate (PIR) is the most common insulation material used in foam-insulated panels. PIR expands rapidly when sprayed onto the metal profile and bonds to it without the need for an adhesive. This property makes it ideally suited to the type of continuous manufacturing process employed by the larger manufacturers of foam-filled panels. Alternatively, rigid slabs of mineral wool or other insulating materials may be bonded to the metal sheets using an adhesive. This method is commonly used for flat-faced wall panels. 2.4 Standing seam systems ‘Standing seam’ or ‘secret fix’ systems use a specially designed profile for the weather sheet, which incorporates a clipped joint between adjacent sheets. This eliminates the need for exposed fasteners and improves the weather tightness of the cladding system. Consequently, standing seam systems may be used on very low roof slopes (down to 1º compared to 4º for systems with exposed fasteners). Insulated panel systems are also available with a standing seam joint in the weather sheet. Standing seam sheeting can be manufactured from steel or aluminium. A typical standing seam system is shown in Figure 2.7. 5 3 4 1 2 1 Outer sheeting 2 Slope 3 Standing seam clip 4 Inner sheeting 5 Insulation Figure 2.7 Standing seam roof cladding The disadvantage of this system is that significantly less restraint is provided to the purlins than with a conventionally fixed system. Nevertheless, a correctly fixed liner will provide adequate restraint. Further information on standing seam cladding systems may be obtained from MCRMA Technical Paper 3 Secret fix roofing design guide [3] and also from ECCS-TC7 Publication 41 Good practice in steel cladding and roofing [6] .