landscaping & external works
Casting the ideal contender for restoration roles
Conservation and architectural drivers are leading to an increased use of cast stone as a substitute for quarried stone. Simon Scott of Haddonstone compares the materials options for specifiers.
stone. Looking at the two types of materials available, it is clear that cast stone is the preferred choice for architects. There have been more imitations of stone than any other
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natural building material and the incredibly versatile cast stone is a prime example. The ability to mould cast stone to almost any shape means you can create new designs or faithfully reproduce replicas that are virtually indistinguishable from an original. The cast stone material matures and weathers like natural stone yet costs significantly less than quarried stone –making it an ideal solution for a restoration project.
Scarborough fair A fine example of the use of cast stone for restoration is demon- strated on the restored Scarborough Spa, a Grade II listed build- ing built in the 19th century. The architectural stonework detail of the building was subject to exposure of salt water from the North Sea. Therefore a robust material was required in order to restore the building to its former glory. Following strenuous salt crystallisation and water absorption tests conducted by the BRE laboratories, it was decided to commission a cast stone manu- facturer for the restoration.
n appreciation of the past and the need to conserve historic buildings and architecture has led to an .increased use of case stone as a substitute to quarried
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Production techniques: getting the mix right
The finest forms of cast limestone are manufactured using a semi-dry mix that creates a surface texture similar to Portland stone or natural limestone. The principal materials of semi-dry cast stone are limestone, white cement, sand and a very small amount of water, giving the mix a damp feel. A reputable manufacturer will ensure that every single batch
of raw material is quality checked to ensure complete control of the production process and enable a high quality end product. The semi-dry cast material is gradually packed into moulds using pneumatic hand tools. The material is usually left overnight to cure before the stone can be revealed in all its glory. Again, reputable manufacturers will employ a curing system
to prevent water loss and ensure that the product achieves optimum strength in excess of relevant British standards. This would ensure that architects, developers and private clients can have every confidence in the durability of the product for their restoration project. There are alternatives to the dry cast mix in the form of
wet-cast and fibre reinforced stonework production. The unique wet cast production technique produces a denser cast
Cast stonework restored to its former glory at Scarborough Spa
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