Portland Stone was traditionally used as a loadbearing masonry material, but at the turn of the 19th century the steel frame was introduced and the structure no longer relied on stone for its support. The stone could be reduced in thicknesses particularly where it clad the steel columns and the beams, thereby saving costs.
The pleasing aesthetic qualities of the stone ensured its continuing use, but now only as a non-load bearing facing bonded to brickwork. This method of construction relied on the strength of the bond for its stability and it was unusual to find any fixings being used. This style of construction was at its peak in the inter war period of the 1920's and 30's.
Following the Second World War and the shortage of steel, the steel frame was replaced with concrete and in an attempt to save costs, the stone was further reduced in thickness, although usually bonded with or built tight against the infill brick backing walls.
As construction techniques improved and materials used for the backing structure was changed to concrete blocks, the stone became true cladding relying entirely on the fixings, originally copper alloys but subsequently replaced by stainless steel for its support and restraint. This style of cladding became the most common way to fix Portland Stone, and is described in the technical section of this website as 'Traditional Cladding'
Along with the traditional, hand fixed, cladding, is the stone on pre-cast. Large concrete panels became popular from the 1950's, the techniques being imported from the USA. Stone used in this way is subject to little or no load, relying on its attachment to the concrete using a series of metal pins.
Further changes in the style of cladding during the 1980's and 90's has resulted in the introduction of rainscreen and stone faced curtain walling. This method of cladding often allows for the stone thickness to be reduced further as each individual stone is tied back to the backing structure. The backing structure is often a metal framework system.
Albion Stone provide recognised specifications equivalent to the industry standard: NBS specification. Available free issue assisting design teams compile RIBA Stage E & F documentation ready for tender.
For advice or assistance, please feel free to contact us.