The adventures of thin bed
The design potential of brickwork can be improved using thinbed mortar, as shown at UWE Bristol's school of architecture
Thin-bed masonry has become increasingly popular on the continent in both the commercial and housing sectors.Now architects in the UK are beginning to recognise that this technique offers aesthetic and structural advantages. It is strong, durable and gives the building an almost monolithic appearance.
The UK's first large-scale project using thin-bed technology - a threestorey building at the Frenchay Campus for the School of Architecture and Planning at the University of the West of England in Bristol - has recently been completed. Designed by White Design and using Hanson Brick, thin-bed glued joints were selected as an affordable elevational treatment. The design-and-build team sought to develop a solution that would offer stack-bonded modular compositions more cheaply than conventional construction.
The project was extremely successful, allegedly due in part to the main contractor Wilmott Dixon taking a lead from former board member Sir Michael Latham's Movement for Innovation. Having sent its entire brick-laying team to Belgium for an intensive training course on thin-bed technology, for example, the contractor also informally partnered the university and built a number of demonstration panels on site.
In summary, the system is economical - it gives more for less by using less mortar and being significantly cheaper than similar cladding solutions. Socially, it promotes rather than replaces a long-established trade and offers tradesmen the opportunity to develop a new form of bricklaying expertise.
And environmentally, with higher performance, fewer components and reduced maintenance costs, the technology has positive credentials.
Jake Rolyn is a freelance writer
CLIENT University of Bristol
ARCHITECT White Design
QUANTITY SURVEYOR Turner & Townsend
STRUCTURAL ENGINEER Mander Structural Design
PROJECT VALUE £2.35 million
Depending on the kind of brick used, the joints will be between 2-6mm wide. Joints in a traditional brick facade account for approximately 20 per cent of the surface. The colour of the joint therefore plays a strong role in the finished appearance. Using thin-bed masonry, the thickness of the joint is reduced, accounting for as little as four per cent of the facade. In addition, as the glue mortar is recessed it appears as little more than a thin line of shade, so the colour of the wall is completely determined by the colour of the brick.
Laid well, with nominal glued joints and exceptionally strong adhesive, a thin-bed masonry facade is almost maintenance-free.
By virtue of its strength, it can accept tensile stresses that a traditional mortar cannot. This allows architects greater flexibility in the way they use bricks, and it is possible, theoretically, to use the frog of the brick as the facing side, making it a feature of the elevation.
After only one day the glue joint reaches the binding strength that a traditional mortar achieves after 28 days - reducing the risk of efflorescence and storm or rain damage.
Glue mortar has the advantage of being water-repellent. Provided there is a consistent application of adhesive, every brick is surrounded by a water-repelling layer and as a result the bricks can no longer exchange water with each other. This makes large concentrations of water in a gable and saturated facades almost a thing of the past.
However, this does not mean that the facade becomes totally water-resistant - water barriers and damp-proof courses have to be applied as usual.
Two strings of glue mortar are applied on the laying bed of the fresh brickwork. To create the vertical joints some bricks are put in a rack, headers up, so that the double string can be applied across the headers of those bricks.
Although efficient, thin-bed masonry is slightly more expensive than traditional brickwork. This is mainly due to the equipment and the cost of the glue mortar, but also due to it being a more exclusive technique.
Paul Rogatzki, Hanson Brick