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Pushing the envelope

CLADDING: Our neighbours are having fun with brick. Michael Hammett sees how it all ties up

In Britain, brick masonry has a long uninterrupted history of use since early mediaeval times and we tend to regard the structural imagery of brickwork as sacrosanct, even when we use it as a cladding to other structural systems. Our neighbours in Europe are not inhibited by such a puritan outlook and are much more adventurous. . . even outlandish!

In these three new buildings the brickwork is clad to framed structures.

Freed from the inhibitions of a structural function, the architects have responded by creating truly bizzare brickwork.

Neuer Zollhof, Dusseldorf Architect: Frank Gehry

Plain, but certainly not plane, the brickwork cladding to a reinforced concrete structure is tilted and artfully misaligned to create the distressed crumpled form of this development. The concrete structure has in situ reinforced concrete inclined wall panels which are the inner leaves of the external cavity walls. The outer leaves are of smooth red wirecut bricks.

The brickwork is jointed in cement/sand mortar and supported at floor levels on light stainless steel angles spanning between stainless steel standoff brackets at 500mm centres to provide a cavity approximately 100mm wide. Similar support angles and brackets support brickwork at the heads of window openings.

Between angle supports, lateral loads, from wind and the horizontal load component of the inclined plane of brickwork, are transferred to the reinforced concrete inner leaf by stainless steel wire ties. These are fixed into the concrete at approximately 450mm horizontal and vertical spacing and subsequently built into brickwork bed joints (see diagram, top left). The brickwork appears to be quite precariously out of plumb, but it did not require temporary support during construction and is securely stabilised.

Netherlands Openluchtmuseum, Arnhem Architect : Mecanoo Architecten b. v

Plane, but certainly not plain, the brickwork here is cladding secured to a steel-framed structure. The amazing variety of bond patterns is enhanced by a variety of bricks and the joints were pointed with different coloured mortars. Mortar joint profiles too were varied. The whole effect is redolent of rich, luxurious Kaffe Fassett knitting.

Wall-tie fixing to the steel frame allowed lateral and vertical adjustment so that the ties could be located in bed joints regardless of the irregular spacing of courses. Bed-joint reinforcement in areas of stack-bonded work compensates for the loss of bonding normally provided by overlapping bricks.

Crawford Art Gallery Extension, Cork Architect: Erick van Egeraat Associated Architects

Neither plane nor plain, this is gravity-defying brickwork and a far cry from tradition. It is brickwork built of bricks jointed in mortar, but the mortar is an innovative thin-joint adhesive formulation developed by KNB, the Dutch trade association of brick manufacturers. Its recipe is secret, but it is believed to have a high cement content and adhesive additives. It is quick setting (it stiffens within about seven minutes and sets within 30) and has a very strong bond.

The sinuous curved form of the cladding takes its shape from a 152mm-thick reinforced concrete shell cast in situ between two layers of metal decking. The inner components of adjustable two-part wall ties were resin-fixed into the concrete, stood off and masked to allow for 80mm-thick sprayed thermal insulation and bituminous waterproofing to be applied to its outside. Outer components of the ties were connected, adjusted and built into brickwork bed joints.

Allowing a 40mm clear cavity, the bricks were fixed with the special mortar, its quick-setting, high-bond adhesive properties permitting construction out of plumb without formwork. As the brickwork shell curved over the top of the structure, temporary packing pieces were used to give support while the mortar set.

KNB approved of the application and, following checks by its structural engineers of the design detail, construction method, site operatives and work in progress, it provided a warranty of satisfactory performance.

The thin joints of this new system (4-5mm) reduce the colouring influence of the mortar on the overall appearance of the brickwork and the brick colour has a correspondingly greater impact. At Cork the particular appearance of thin jointed work seems to enhance the shell-like character of the brickwork forms.

TECHNICAL NOTES

Photography Christian Richters Diagram Halfen Germany

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