Terracotta tile MANUFACTURINGFAIENCE AND TERRAC·OTTA A view from Ibstock Hathernware, the terracotta and faience company within the Ibstock Group The two top storeys of this 1930s terracotta building in Leeds were completely destroyed by fire which also damaged the rest of the building. Jbstock Hathernware supplied replacement terracotta for its successfu,restoration. CONTEXT SY Before embarking on the various stages involved in the manufacture of terracotta and faience, it is worth first taking the following considerations into account. The manufacture of these two building materials is more akin to art than engineering. As every piece is hand made, no two pieces, even from the same mould, will be identical and this has to be borne in mind during design. Blocks will vary slightly from the design size due to the contraction factor during manufacture. There is normally an 8% shrinkage which occurs during drying and firing, and regular joints are needed to accommodate these slight discrepancies. Very large blocks should be avoided wherever possible and, at the very least, a proportional balance between length, breadth and height should be aimed for. Variation in colour shade with both terracotta and faience can be expected from block to block, which greatly adds to its aesthetic appeal. Both materials are extremely strong in compression but weak in tension. Every effort must therefore be exercised to take advantage of their load-bearing capabilities and avoid tensile stress. Similarly, it can be expected that glazes will craze at some time during their life. This is purely cosmetic and does not detract in anyway whatever from the durability of the material. Finally, it has to be remembered that after manufacture terracotta and faience expand slightly whereas concrete shrinks. When they are used in conjunction therefore, allowance for movement joints should be made. DESIGN The first stage in the manufacturing process is to prepare elevational drawings at I :20 scale or larger, based on the architect's design requirements. This would, of course, necessitate a site survey in the case of a restoration 11
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