STRUCTURAL ELEMENTS The devil’s in the detailing
Alex Patrick-Smith of Ketley Brick discusses the performance considerations that need to be borne in mind when choosing increasingly popular textured brickwork facades
B
rick, which has of course been a major part of the British built environment for thousands of years, is undergoing a renaissance. The material is finding fresh audiences for the way it can add texture to buildings in exciting, innovative and contemporary ways. Not surprisingly, new generations of architects are seeing the potential of ‘hit and miss’ cladding techniques and projecting brickwork on large scale urban projects as they seek to push boundaries with more ambitious and visually striking facades, such as those seen on the 2017 RIBA National Award winning Victoria Gate in Leeds. Modern methods of construction, using digital imaging and precast concrete, have further opened up design possibilities, enabling complicated textured brickwork patterns with a complexity of detail, which would have been impossible with traditional construction, while adding the associated advantages of faster and more efficient off-site construction. However, as the design potential for more ambitious and elaborate facades grows, so do the technical and physical demands made on projecting brickwork in exposed applications. Traditionally, F2 has been the recognised standard for frost resistance of facing bricks, with ‘Class A’ engineering bricks – having high compressive strength and low water absorption – offering the highest level of durability. However, the fact that F2 certification offers the highest frost resistance classification for facing bricks in flush finished brickwork does not guarantee that the same bricks can withstand the more severe omnidirectional freeze-thaw conditions seen in exposed applications. In fact, in textured brickwork tests, many F2 facing bricks have actually experienced failures which could potentially result in the degradation of the bricks when they are projecting. In reality, the level of freeze-thawing experienced by projecting brickwork is far more severe than conventional flush
ADF MAY 2019
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© Alex Upton Photography
brickwork and closer to in fact that of pavers. As the ‘bed’ face of the headers is more exposed to the elements, there is always the potential for the rainwater to sit on the ‘bed,’ causing the brickwork to become saturated, and then be vulnerable to freezing and deterioration. Despite the need for bricks with much lower water absorption rates in exposed applications, there is currently no industry wide standard in the UK specifically for ‘hit and miss’ or projecting brickwork, unlike in Holland and parts of Europe, where tougher tests similar to paver freeze-thaw tests are beginning to be introduced.
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