64 RCI 0714

RCI JULY 2014

to suit the ambient conditions before the membrane is laid? • Has the membrane been suitably loaded (e.g. water-filled roller) immediately after laying? Part Three of this series will look at other attachment options, rules for detailing and where the few failed roofs went wrong. References: 1. ID/1/2009: Mechanical fixings for rigid Polyisocyanurate (PIR) and Polyurethane (PUR) roofboards beneath single-ply waterproofing membranes. 2. MOAT 50:1992 ‘Technical guidelines for the assessment of thermal insulation systems intended for supporting waterproof coverings on flat and sloping roofs’. 3. ANSI-SPRI IA-1-2005 Standard field test procedure for determining the mechanical uplift resistance of insulation adhesives over various substrates SPRA MATTERS Got a single ply roofing query or issue you would like to discuss? Contact The SPRA Helpline: Tel: 0115 914 4445 Fax: 0115 974 9827 www.spra.co.uk The same principles apply to the single ply membrane itself. Its attachment will generally be by a separate set of fasteners, which transfer wind load directly to the deck. If as in some proprietary systems the same fasteners are used to secure all three components, then this increased loading should be factored into their layout and number per unit area. Experience over forty years in the UK shows that if these rules – and correct calculation – are followed, the method is extremely reliable and existing safety factors are adequate. So what about adhesion? Adhered systems Adhered systems are altogether different because wind load is transferred to the deck in a chain of attachment from the exposed single ply membrane to the deck: Rigorous testing of the ‘factory conditions’ interfaces is a pre-condition for approval by SPRA membrane manufacturers. They need certainty that when tested against established European (UEAtc) and US (ANSI-SPRI) norms, the boards will not only be compatible with the adhesives they supply but also capable of high resistance to delamination. The rest relies upon sound site practice in the context of the UK’s variable temperature, humidity and rainfall conditions – a bigger challenge than many realise. That places huge reliance upon the skill and attitude of the installer, which is why SPRA requires not only a high standard of training delivered by manufacturers, but also a training target of achievement of the Vocational Qualification ‘Applied waterproof membranes – single ply roofing’ at Level 2. The critical installation factors for resistance to wind load are: • Is the deck dry and suitably prepared for application of adhesive or self-adhesive products? • Is the correct adhesive and coverage rate in use to secure the insulation? • Has the insulation been loaded following installation, to ensure a good key to the adhesive? • Is the insulation facing dry and clean ready for application of the membrane adhesive? • Is the correct membrane adhesive and coverage rate in use? • Has the adhesive reached the optimum tackiness Interface (warm roof) Where formed Single ply membrane to insulation facing Site Insulation facing to insulation core Factory conditions Insulation core Factory conditions Insulation core to facing (underside) Factory conditions Insulation facing to vapour control layer Site Vapour control layer to deck Site Wet Roof Leak Detectors Dry Roof Leak Detectors Buckleys are the leading man destructive testing products detecting defects in non-cond including: Single Ply, Bitume Applied Systems in both Wet Call us on +44 (0)1303 278888 email sales@buckleys.co.uk or visit www.buckleys.co.uk www.buckleysinternational.com Roof le testing g come r or shin Buckleys (UVRAL) Ltd. Buckleys House, Unit G, Concept Court, Shearway Road, Shearway Business Park, Folkestone, Kent. CT19 4RG. United Kingdom. Manufacturers in specialist test equipment


RCI JULY 2014
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