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RCI March 2018

Project1_Layout 1 07/05/2013 CLADDING & SHEETING The roofline is a tricky area where two expanses of different materials meet – the roof tiles and the brick wall. Each does its job well, but neither is completely satisfactory in covering this crucial junction. Consequently, the roof-to-wall union has to be defended rigorously against water and wind ingress, whilst at the same time, allowing proper ventilation of the roof void to take place. But, you may ask: “Why ventilate the roof void at all? Why not seal it all up and be done?” A perfectly valid question, but the answer is rot. Protecting against rot Every day, building occupants generate huge amounts of hot air, which is laden with water vapour. And, as we all know, hot air rises. In addition to this, moisture occurs naturally in the air outside, and a lot of this damp air finds its way into the roof void. Now, consider that the average attic is a cold uninviting place that encourages moisture to condense on its vulnerable timber surfaces, and you have the perfect micro-world in which mold and rot can take hold if the airborne moisture is not kept moving. Roofline systems, the broad, industry term to describe fascias, soffits, bargeboards and all the associated ventilation components, are good at protecting the eaves, while fully venting them. Timber was for many years, the preferred material for roofline components, but a softwood fascia board is unlikely to survive more than a decade, especially if it doesn’t receive regular maintenance. 048 MARCH 2018 RCIMAG.COM Let’s look at the roofline Dave Osborne, technical manager at Swish Building Products, takes a look at the roofline – the part of a building where the roof structure meets the walls – and where detailing needs careful consideration to ensure the long-term integrity of the building envelope Cellular PVC: the material of today Cellular PVC is probably the most efficient material for use at the roofline, because it costs roughly the same as timber to install and requires no maintenance. Most importantly, especially from any landlord’s point of view, when it is installed correctly, it will probably last the lifetime of the dwelling. As far as roof void ventilation is concerned, the preferred method these days is to use a continuous venting unit that sits on top of the fascia board and supports the roofing felt and the lower row of tiles. This method does away with slots or ugly vent discs set into the soffit board On a very practical note, Cellular PVC roofline systems are also good at providing both visual and physical support for the other essential components in rainwater management – guttering and downpipe systems with all the attendant bracketry and fixings. Coordinating finishes Cellular PVC is an extruded, foamed material with an integral smooth and durable skin. A wide range of colours and foil finishes are available, providing a considerable degree of flexibility in coordinating with popular window and door styles, as well as coloured rainwater management systems. Cellular PVC Roofline products from Swish Building Products also represent an environmentally responsible use of plastics. Not only do they not contain CFCs, lead or cadmium, which are considered harmful to the environment, but the company itself has also taken huge strides over the last decade in reducing its CO2 footprint and use of water in manufacturing. Cellular PVC also has a very long lifespan and when replaced, can be fully recycled. Complementary rainwater systems Swish also manufactures a complementary range of guttering, fall pipes and attendant bracketry, all designed to efficiently collect and dispose of rainwater run-off from roofs. Swish standard rainwater systems all contain a high proportion of recycled materials, and the company is the only UK plastics manufacturer to be awarded BES 6001 Responsible Sourcing Certification for both its roofline and rainwater products. www.swishbp.co.uk Fascias, soffits, bargeboards and ventilation components are all good at protecting and ventilating the eaves and roof-space Cellular PVC boarding is the most efficient material for use at the roofline


RCI March 2018
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