32 RCI 0614

RCI June 2014

SANDTOFT SAYS When I started in the roofing business many years ago, I worked for a small independent roof tile manufacturer. In those days, specifications were usually based on the leading tile manufacturer’s products; the best we could hope for was to persuade the architect to include the words ‘or other similar approved’ in the specification, which would allow the consideration of alternative products. This then enabled us to offer our products and, in the process, meant that product costs remained competitive. However, the problem with this approach is that a variety of products from different suppliers may be installed, with little regard to their compatibility within the overall roof system. A building is a product constructed from many components, just in the same way that a car or a piece of electronic equipment is constructed from many components, each one being very carefully specified. Yet buildings are probably the only product that can be put together without fully specifying each and every component. So why is a complete specification important? The roof is a system and should be regarded as such, with each component of that system fully compatible with every other, not just in terms of physical fit, but also appearance and, most importantly, performance. For example, the introduction of modern ‘breathable’ underlays into UK roof construction has meant that careful consideration must be given to the type and amount of ventilation, as well as to the way in which the underlay is installed. It is important to understand the performance characteristics of the particular underlay being used, as not all breathable underlays are the same. Some are vapour permeable and some are vapour and air permeable, both providing different levels of performance, therefore it is important that the other, related roof components and systems match the particular underlay to ensure the correct level of roof space ventilation is provided to prevent harmful condensation build-up. 032 JUNE 2014 RCIMAG.COM Specification, specification, specification! By John Mercer, technical director at Sandtoft, a Wienerberger brand Performance characteristics The industry is moving away from a reliance on mortar to keep things in place, and towards dry fix, with systems for use at, for example the ridge, hip and verge. These are generally proprietary systems, requiring their own unique installation methods. Therefore, it is important to understand the performance characteristics of each system to be able to assess its suitability within a particular roof design. The advantage of using a ‘whole-roof’ specification is that purpose-made, fully compatible dry fix systems can be specified, rather than third party universal systems. Universal systems, by their very nature, are designed to fit a whole range of different products, therefore they will not fit as well as a purpose-designed system, not just in the physical fit of the components, but also appearance and colour – many accessories designed by roof tile manufacturers to suit particular roof tiles are colour and texture matched to the roof tiles. With regard to the mechanical fixing of the tiles, fittings and accessories, a specification written by the roof tile manufacturer includes the appropriate type and number of fixings. The tile manufacturer determines the performance of its fixings by test in accordance with the requirements of the relevant Standard. Therefore, it is important to use the manufacturer’s approved fixings to ensure the finished roof provides the required resistance to predicted wind loads. The risk for the client, or indeed for anyone involved in the whole design-to-build process, is that if the roof is not properly specified or if components have been substituted for nonspecified products and anything goes wrong with the roof, there will not be a clear line of responsibility. A great example of the advantage of whole roof specifications is Wienerberger’s RoofSpec system. This provides the client with total piece of mind by guaranteeing that the specification fully complies with all current legislation and Codes of Practice. In addition, by installing fully in John Mercer, technical director at Sandtoft accordance with the specification, using the products specified, the roof system is guaranteed to perform properly and remain watertight and durable. This is something that is extremely important to clients such as social housing owners who require a long period of low or maintenancefree performance. In summary – To ensure the optimum performance of the whole roof system only use fittings and accessories specified by the tile manufacturer. – Bespoke accessories and systems designed to fit particular roof tiles are generally a better fit and many are a closer match in colour and texture. – A comprehensive specification will ensure that the roof design and installation complies with Building Regulations and standards. – Reduce the potential risk from defects by adhering to a comprehensive specification – try to take advantage of specifications backed by the manufacturer’s warranty. www.sandtoft.com “For example, the introduction of modern ‘breathable’ underlays into UK roof construction has meant that careful consideration must be given to the type and amount of ventilation, as well as to the way in which the underlay is installed”


RCI June 2014
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