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RCI January 2018

FLAT ROOFING & WATERPROOFING SYSTEMS Five steps to welding your membrane securely SIG Design & Technology’s Steve Cleminson discusses how to weld membranes securely with a five-point guide to ‘welding success’ Cleaning and test welding Achieving a good weld relies on a number of factors starting with the question does the seam / area need cleaned? There should be no need to clean weld area on newly unwrapped membrane but if any of the pieces of membrane are old or soiled, first they should be prepared by scrubbing with a brush using warm soapy water, and then thoroughly rinsed and allowed to dry prior to the use of an applicable cleaner. Perform a test weld to check the need for further cleaning. The cleaning process should be repeated as necessary depending on the level of contamination and additional chemical cleaning may be required. Test welding should always be undertaken at the beginning of each work session to ensure settings on the gun and speed of weld are correctly balanced with the pressure being applied. Tack weld Next, make sure the membrane doesn’t move as we are welding it. The membranes should be tack welded together with a light, breakable tack. Note that it is essential that these tacks are breakable, especially with mechanically fixed installations. Remember that when the membrane pillows during high winds these tacks will be put under stress and if they don’t break then the membrane could become ‘holed’. Once broken, any stresses are transferred to the back of the pre-weld so that the load is uniformly distributed and there won’t be any ‘holing’ at the overlap. Pre-weld Membrane seams should usually be undertaken in two passes. The first Pass ‘pre-weld’ is set 30mm back from the leading edge and acts as a continuous air trap which ensures minimal heat loss during the final weld stage. 052 JANUARY 2018 RCIMAG.COM Final weld The second weld is completed to the front 30 mm of the weld zone, effectively extending the preweld to the leading edge of the membrane. Weld window Welding must be undertaken within the “weld window” of the membrane to ensure that a secure weld is achieved, refer to manufacturer’s instructions and expect variation on temperature, speed and choice of roller; e.g. reinforced membrane can be welded at higher temperature than unreinforced / detail membrane. Test weld Test welding should always be undertaken at the beginning of each work session to ensure settings on the gun and speed of weld are correctly balanced with the pressure being applied. Seam check Once the seams have completely cooled the seams must be checked using a seam probe. SIG Design & Technology is part of SIG Roofing. We design and supply flat roofing solutions including green roofing, zinc, copper and stainlesssteel roofing and cladding and pitched roof coverings including natural slate and clay tiles. We have put together an 8-step guide to identify the challenges and ensure that a roof’s design meets a building’s requirements. Called #PerfectRoof, the eight steps follow the process from product selection and design expertise through to full guarantees and planned maintenance. www.singleply.co.uk Top 5 tips to think about when welding 1. Power supply The need for a consistent power supply is essential – make sure there aren’t demands being made on the power supply which could lead to fluctuating voltage and a reduction in gun temperature. 2. Keep your nozzle clean Build-up of carbon deposits can occur and interfere with the effectiveness of the weld. Use a wire brush as and when required. 3. Overlap widths Make sure the overlap width corresponds to the membrane type i.e larger for mechanically fixed membranes compared to bonded membranes. 4. Night joints Ensure all laid membrane seams are welded up the same day they are laid and incorporated, as necessary, into any night joints. 5. Protect your gun Make sure that heat guns are correctly cooled down after use, this not only avoids the risk of burn injuries but also help to get the best longevity out of your element – think of hot light bulb pining! Pre-weld Final-weld Tack-weld All images courtesy of IKO


RCI January 2018
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