Selecting the Corrrect FastenerWhen selecting fasteners, allow for the recommended minimum deck penetration or embedment and take into consideration the total build-up of the roof system, including any pressure plate, membrane, insulation, vapour control or separation layers.To select the optimum fastener for tube washer applications, take the total build-up measurement, deduct the selected tube length and allow for deck penetration. Then add 25mm for the fastener within the tube and select the fastener at this length or longer.For example, with an 85mm build-up over 0.7mm steel deck using a 60mm tube; and using the BS-5.8 range of fasteners.