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Technical Envelope


Three colours were developed to


“As the brickwork was coming up, we had to stay on top of the trades to make sure everything was right fi rst time. Once they were mortared there was no going back” Mike Vorster McLaren


mirror the tones of the masonry in the surrounding conversation area, including Old Sessions House. They were laid in a random pattern across the facade, although in certain areas, such as those adjoining the prefabricated lintels, the apparent randomness required meticulous planning to avoid too much repetition and to conceal vertical movement joints. These joints were required to


accommodate minor slab edge defl ections caused by the reduced number of facade columns on the ground fl oor. However, the use of lime mortar, which takes longer to set and is more fl exible than sand mortars, helped cut the number needed. The bricks that would be used during


the day were delivered early in the morning, loaded onto a hoist in the atrium and distributed to the edges of fl oorplates. A cantilevered scaffold was required on the south elevation to enable a private road to remain open. Working with handmade bricks meant


devising a method of quality control to ensure that the alignment of bricks and mortar beds remained consistent. Kolomba bricks have a tendency to


bow and twist slightly, and the mere act of pushing one out of its mould creates a thin lip around its base, so a decision was made to lay them all “lip down”. Each course had to fi t within a 47mm-deep coursing rod (37mm of which was brick, 10mm of mortar) compared with 75mm for a conventional brick. Regular inspections were made by site managers and the architect to ensure standards were met. “The challenge was understanding the


tolerances we had to deal with for these bricks, in all directions, and ensuring there was little to no effect on interfacing elements,” says Vorster. “We had a number of trades working in the same area, including internal dryliners, waterproofi ng, operatives applying mastic around windows. As the brickwork was coming up, we had to stay on top of the trades and making sure that everything was right fi rst time. Once the bricks were mortared there was no turning back.” That attention to detail has paid off,


the fi ne ribbon of buff brick and deep window reveals giving the facade angular defi nition and an organic texture, a combination that also blends happily with the grain of the busy local context. CM


Structural support


Structural support for the building is provided by an insitu reinforced concrete frame, whose columns on the façade are positioned in alternate piers between pairs of windows. The columns are enclosed within the internal layer of the rainscreen system, which comprises a lightweight metal frame, a layer of cementitious board and a layer of foil-faced insulation. A reinforced concrete “brick support


system” was hung from the slab edges of each fl oor to provide a frame for the many thousands of hand-laid bricks,


LEVEL 4 WINDOW BAY ELEVATION


and the heavy precast brick-faced concrete lintels, which were manufactured by Cheshire-based fi rm Ibstock Kevington. The support system comprised a


cantilevered reinforced concrete beam, bolted to, but thermally separate from, the concrete slab. There is an L-shaped steel tray bolted to the outer edge to provide support for bricks above. Where window openings are located, brick-faced precast lintels were bolted to the underside of the beam and brick sills installed above.


WINDOW BAY PLAN


BRICK SPECIAL TYPE FH DOGLEG BRICK SPECIAL TYPE E


IN SITU REINFORCED CONCRETE PRIMARY STRUCTURE


DOUBLE-GLAZED OPENABLE WINDOW VENT


DOUBLE-GLAZED FIXED WINDOW PANEL


SILL BRICK SPECIAL TYPE B CONSTRUCTION MANAGER | JANUARY 2015 | 33


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