Whilst the majority of architectural precast concrete units are specified as wall panels for the external cladding of buildings, they can also be designed to bear greater loads and act as structural elements within the frames of buildings.
Some notable innovative examples include:
Each of the main structural beams running the length of the pool were designed, manufactured and delivered as a set of 3 matched-face-cast concrete units before being post-tensioned together. They were cast using a white concrete mix and their seen faces were polished, as were the matching structural columns and perimeter gutter units. This project was the winner of the 1989 Concrete Society Awards for “outstanding merit in the use of concrete”.
The perimeter beam units at each floor level were cast using a concrete mix to match the colour of the adjacent natural Jura limestone and were finished by acid etching to match their fine rubbed surface texture. The precast beams included fabricated steel boxes to which the steelwork members of the building’s main frame were bolted.
30 Finsbury Square, London
To simply describe the precast concrete units we produced for this project as stone-faced wall panels fails to convey the complexity of their unusual construction. Their nom 75mm natural Portland stone facings were supported and restrained using stainless steel dowels that firstly bridged the 50mm vented cavity behind the stone facings and secondly extended through 50mm of insulation before being set into the precast panel’s reinforced backing concrete. The backing concrete encased structural steel column sections which were incorporated into the building’s main structural frame by bolting.
The increasing demand for architectural precast concrete cladding from the high-rise residential sector since 2000 has also generated a significant requirement for cantilever balcony units. Initially as reconstructed stone finished units, they are supplied with projecting reinforcement so that they can be incorporated into the structural frame by the frame contractor as his casting of the floor slabs proceeds. The specification of the balcony units has been progressively developed to include options for cast-in balustrade fixings, cast-in rainwater hoppers, waterproofing and, in order to reduce on-site working at height, the off-site tiling of the balconies’ top surfaces.
With the architectural trend in the high-rise residential sector for balconies together with slender perimeter columns, designs have been developed for these columns to be structural precast concrete elements. They are progressively stacked and laterally restrained at each floor level through the precast balcony units and similarly incorporated by the frame contractor. For Angel Lane, the structural column and balcony units were produced with reconstructed stone finishes to resemble colours and fine rubbed surface textures of natural Portland and Bath limestones and a silver-grey Cornish granite.
Like Angel Lane, its perimeter column units are also precast concrete units that act as structural elements in the building’s frame. The units however vary in that they are brick-faced on each of their four sides. The balcony units are also brick-faced precast concrete units.