Kaye Alexander examines the details of four aluminium and zinc cladding systems
Rednock School, Cube_Design
Currently on site and due for completion in 2009, Rednock School (above) in Gloucestershire is funded by the government and the Department for Children, Schools and Families, as part of the Building Schools for the Future programme.
The Learning Resource Centre (LRC) is conceived as a focal point, cantilevering over the main entrance. The main challenge was finding a material and a cladding system that could be supported from a steel-frame structure and a secondary support system that could achieve the curved form.
Euroclad manufactured bespoke 3mm powder-coated aluminium panels, which provided the best match with our design aspirations and budget, despite each panel incorporating curves in more than two directions and two planes. The joints had to be discrete and accommodate windows and glazed louvres.
The build-up also had to provide a weather-tight enclosure early on to meet the programme.
The general form was fully developed through the use of 3D CAD models. The Euroclad model was then interrogated to develop detailed two-dimensional sign-off drawings. The form of the LRC pod was refined, resulting in the double curvature of the corners linking the inclined vertical surfaces.
Jane Lock-Smith, managing director, Cube_Design
The Arc, Veretec
The Debenhams store, part of the Arc shopping complex in Bury St Edmunds, opened in March 2009. The exterior features a distinctive sand-cast aluminium cladding system that comprises approximately 3,822 custom-made diamond-shaped panels with 384 pattern shapes.
The panels are fixed to the steelwork via curved galvanised members, which have a clamp attached. These clamps can move in three directions and consequently can hold individual panels in the required position with the correct joint width (30 x 18mm). The panels are lit from behind with blue neon light.
CA Building Products designed and manufactured the panels directly from a digital model, sending files to the manufacturing floor in an almost entirely paperless process.
The structural-engineering design was also completed digitally, using finite element analysis techniques, and the on-site setting-out was driven by information from the master model.
The casting process involved creating moulds out of sand and setting these with epoxy resin. Over 50 parent shapes were created and, from these, a family table of panel variants were generated, which simplified the manufacturing process and reduced costs.
Post-casting, the panels were coated in a clear protective lacquer, similar to that used on the hulls of ships, to give a durable finish.
Keith Morgan, director, Veretec, and Nick Belden, design manager, CA Building Products
Lister Mills, David Morley Architects
The rooftop penthouse pods of this residential conversion are inspired by twisted yarn, a reference to Lister Mills in Bradford’s former function – a silk mill.
We evaluated several forms of construction and cladding. Factors taken into consideration included weight, budget, lifespan, construction programming and the suitability of the material for the scale of the development and its historic masonry.
The cladding solution selected is a zinc standing-seam roof covering, chosen for its malleability, seam alignment, lightness and prepatinated finish. The zinc sheets need to follow a sinuously curved path in order for the seams to appear straight.
The semi-monocoque timber structures comprise a stressed skin with curved ribs, constructed with a combination of plywood and oriented strand board (OSB). These cassettes form the shell that spans between the two steel-edge hoops.
There are around 15,000 computer-cut parts in the roof. The flat parts are designed to slot together into the finished form.
The 300mm-deep space between the ribs is packed with insulation. The faceted outer-panel surface is sheathed with a breather membrane and cross-lined diagonally with 100 x 25mm boarding on softwood battens. This evens out the facets and forms the double-curved surface to take the Rheinzink prepatinated roof covering and also creates a ventilated zone underneath the zinc.
Jennifer Juritz, project architect, David Morley Architects
The Cube, Make
The Cube is a 42,000m² mixed- use development in Birmingham due for completion in 2010. The Cube’s outer elevations are a geometric pattern of double-glazed louvres and anodised aluminium panels, dissolving into an open screen at the upper levels.
The thermally broken unitised cladding system plays a key role in the building’s environmental strategy, allowing inhabitants to tailor the glazing of each facade in response to solar gain.
The Cube incorporates office and retail accommodation on the lower six levels, with residential and hotel accommodation above. Each panel is 1.5m wide and supported from the top and restrained at the base. The difference in floor-to-floor heights – 3.75m for the offices and 3m for residential and hotel – disguised by a fine-grain 750mm grid that runs across the entire facade.
The distinguishing feature of the cladding is the variety of bronze and natural anodised aluminium boxes in different shapes configured from a 750mm square. The boxes are fabricated with non-visible welds and discreet open joints that ventilate, drain and ensure pressure equalisation. Each is lined to prevent acoustic drumming, incorporates a drip detail and projects 67, 133 or 200mm from the glass line.
Paul Scott, partner, Make