|Client:||London Borough of Lambeth|
|Architect:||John Pelling and Partners|
|Contractor:||Collinstown Construction Ltd.|
|Material:||W.T. Lamb & Sons replacement red Architectural Terracotta and Smooth Red Facing Bricks to match existing material|
Built in the late nineteenth century Streatham Hill Mansions are typical of the period with much ornamentation particularly in Architectural Terracotta. Lambs were approached by Collinstown Construction to provide prices for the supply of Imperial Smooth red Facings to match the existing brickwork and subsequently matching Architectural Terracotta blocks.
Failure of the original terracotta units was mostly due to the rusting of non ferrous metal fixings and their expansion inside the units creating cracks and laminations.
With prices and availabilities agreed and the architect reassured that Lambs could supply to requirements Collinstown Construction placed their order just before Christmas 2003 following the earlier order for bricks. It was of great benefit to Lambs Terracotta Workshop that examples of the original terracotta units were available to be taken away for copying because this obviated the necessity of extensive site surveys.
Terracotta shrinks at two distinct stages during its manufacture so it is not possible to make moulds simply by taking casts from the original pieces. Pinnacles and intricate blocks have to have models, up to 20% bigger than the original, carved so that oversized moulds can be taken to allow for this shrinkage. Runs of string courses and simpler units can have the mould made directly bigger by copying the profile and making an enlarged profile gauge to shape the plaster mould.
Blended clays were prepared to match the original colours and the plaster moulds were carefully hand filled ensuring that no voids were left. As the clay is pressed and worked into the mould it was worked in different directions to give greater stability and strength to the finished block. After weeks of drying the units were taken to the computerised kiln and fire to program to ensure that no under fired units resulted. During firing the terracotta develops a fire skin which is important in the weathering of the block once it is in the building, it is sometimes due to the removal of this fire skin during restoration that causes later failure.
With the successful completion of this project Lambs are looking forward to opportunity to quote for further work in South London.
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