Clay tiles - a natural product often copied, but never equalled The Chairman of the CRTC explains why genuine clay roof tiles are a cut above the rest: A look skywards today reveals many different styles and types of roofing covering our buildings. Nowadays specifiers have an enormous selection of roofing materials to choose from, but this wasn't always the case. The main reason clay roof tiles enjoy such popularity is because of the product itself. Clay roof tiles have been around since the 13th century and have proven their durability. Their colour is permanent and, unlike other materials, does not fade with time. Indeed, the elements work with the clay to produce a weathered and mellow appearance, improving their looks with age. What is more, clay tiles are fire resistant, able to withstand harsh chemicals and are not susceptible to biological degradation, they do not harbour excessive mould growth and are not affected by extremes of heat or cold. These properties coupled with the fact that clay tiles are a natural and sustainable product (qualities that are appreciated by an increasingly discerning public who care about the environment) make clay tiles an ideal roofing option for new build and refurbishment work. One of the greatest challenges to architects, planners and designers must be to consider not only how the building will look in the immediate future, but also how it will look in 10, 20, 40, 50, or 100 years time. This is the greatest legacy that they can bequeath to future generations - an architecture that is as beautiful, if not more so, in decades to come as it was when first constructed. The roof is arguably the single most exposed face of any structure! It has to withstand rain, wind, ice, ultra-violet light and, increasingly, the effects of damaging acids caused by atmospheric pollution. All the more reason for specifiers to choose a natural roofing product that is able to sustain these harsh elements and still mellow and improve with age. Not only will a clay roof tile hold an authentic time worn appeal, but its low maintenance cost will mean that its whole life cost is relatively low - a factor which specifiers should certainly consider when comparing the costs of different roofing materials. The life span of a clay tile is influenced by the type of clay, the way it is manufactured, the dampness of the atmosphere, the position of the building and the pitch of the roof. All these factors will influence the speed of the weathering process. But, the colour of genuine clay roof tiles is permanent and they are highly regarded for this attribute. A tile's colour stems from the natural occurrence of trace elements of iron, chrome and nickel found in the clay. By controlling the kiln temperature, the amount of oxygen present during the firing process and varying the amounts of manganese added to the moulding sand, the manufacturer is able to produce a spectrum of permanent natural colours ranging from almost black to bright red. Between them, the six members of the CRTC produce tiles in more than 50 colours ranging from deep reds, browns and oranges to the plum coloured hues of heather and the muted blues of the Staffordshire tiles. Despite any additives during the manufacturing process, the natural colour of a clay tile will continue to "shine through" during the weathering process and will not erode over time. If in doubt about the authenticity of a tile's colour, a quick look at the reverse of the tile will indicate its true, untainted colour. The colour of clay tiles is particularly important to specifiers who undertake refurbishment or building extension projects. It is crucial they ensure that the new tiles laid match the colour and style of the original tiles. The weathering properties of clay tiles ensure that they are able to blend in with old, original tiles and therefore make them an ideal roofing material for refurbishment projects. Where necessary, new tiles with an artificially aged appearance can be used to blend in with historic products. The refurbishment market demand for clay tiles is met by the six members of the CRTC which produce traditional handmade and machine-made clay tiles that carefully match the colour and technical specifications of original tiles dating back hundreds of years. The members have over 1,000 years experience between them and are still able to manufacture tiles using traditional methods, passed down through the ages by craftsmen, allowing the roofs of beautiful historic buildings to be restored to their former glory.       The following case studies illustrate the fact that clay roof tiles are most definitely able to stand the test of time (click the images to see bigger versions): CRTC member Dreadnought Tiles' plain clay tiles in Plum Red were used on this property, tiled in 1953 in Kingswinford, West Midlands. It might have been expected that the extra exposure suffered by the tiles on the pitched roofs would have resulted in a loss of colour compared with the greater protection enjoyed by the tiles on the vertical areas but, 50 years on, both areas are testimony to the longevity of natural burnt clay colours.     In 1988 Dreadnought Tiles supplied a mixture of tiles for the roof of Safeways Supermarket at Folkestone (above). Thirteen years later (below) the colours of the roof tiles have improved with age and are even stronger!