|Stone has been commonly used as a construction material across the world for several thousand years. Its inherent strength and durability made it an essential part in construction. As construction has evolved globally and man made products have become more suitable to modern building design, the use of stone has shifted away from a structural role and more into the realms of cladding and aesthetic detailing.|
Stone veneers are common in western Europe, particularly the UK whereby man-made stones are usually fixed over existing brick walls. The practice was common in the 1960’s and the 1970’s. Although stone cladding has been in New Zealand since the 1960’s it is fairly rare, but as building design diversifies it is likely to become a more common alternative to mainstream cladding systems. New Zealand systems include Natural Stone, the Firth Stone range and natural stone systems, such as Schist. Split Stone produced by Firth was originally used on State houses in the 1960’s.
Split stone is a man made product of regular size and uniformity. The stone is cast in blocks which are then split vertically to create two blocks with a rough, irregular, natural looking stone face. As this product is man-made, a range of colours and consistencies are available. The split stone cladding is usually installed as a brick veneer over a 40 to 70 mm cavity with a rebated concrete floor slab providing support to the heavy cladding. Due to the additional weight of the split stone cladding (as opposed to a typical brick veneer), engineering assistance should be sought for seismic restraint and cladding lintels.
The split stone cladding is a porous product and as such should be designed with a drained and ventilated cavity system as moisture ingress beyond the outer face of the cladding is inevitable. Other installation methods for split stone cladding have been tried including adhering split stone to a fibre cement backer with additional mechanical support at intermediate courses. When designing such a system, thought should be given to the durability of the components, including the backer and the adhesive used to bond the split stone. This cladding installation is beyond any Building Code acceptable solution and should be approached with caution.
The split stone cladding can be installed with a brick-like stretcher bond layout, or stack bonded to create consistent horizontal and vertical grid lines. The mix of a rough natural looking face block and unnatural square shape can be very appealing in the right environment. This type of cladding will no doubt appeal to those looking for a contemporary style of architecture whilst maintaining a natural feel.
Further information on split stone cladding can be obtained from the manufacturers of the blocks at www.firth.co.nz.
By Jake Woolgar