Tate Modern Gallery's Ultra-Futuristic Extension - page 5 of 6
The Tate Modern rear of the present building, scaffolding. © Photo: the wub
This is tied to the concrete frame and both structures are founded on piled foundations to ensure continuity through the two buildings.
A storey-height truss was required at the level 02 west elevation to span over UK Power Network’s assets and long span transfer beams were installed to achieve the entrance openings.
At level 05 of the Switch House, the sloping north elevation of the tower meets the roof of the level 04 gallery. With no possibility of continuing the north elevation into the gallery space, a 1.8 m deep spreader beam was installed.
This distributes the loads from the perimeter structure into the roof beams which, in turn, transfer the load to the core and northern Switch House columns.
In order to distribute the loads effectively, whilst not allowing any deflection to occur, the spreader beam was supported on a series of 16 jacks. These were closely monitored during the construction of the north elevation, and jacking operations undertaken at strategic times to minimise impact on the construction above.
Once the final brick was installed, the jacks were grouted with maximum differential movement between roof beams having been limited to the required 2 mm.
To achieve the tolerances required for installation of the glazing and brickwork it was essential that the deflection of the structural frame to the perimeter of both the tower and Switch House buildings was limited. Although complicated by the geometry of the tower and the various types of transfer structures, deflection limits of 1 in 1000 were achieved.
A Unique Brick Façade
Truly an architectural wonder, the building’s unique perforated brick façade envelopes the structural frame, acting as a rain screen.
The corners and creases are column free, emphasising the continuity of the surface, whilst providing ‘open views’ to the exterior.
In total 336,000 bricks in 212 different types were installed between August 2014 and February 2016, using a new system that could be installed in ‘all-weather’.
The architectural intention was for the wall to be ‘movement joint’ free and this was a key consideration in developing the most suitable brickwork system.
Accommodation of the relevant tolerances in the façade, manufacture and installation were critical to achieving a successful building envelope.
Bespoke 3D setting out tools were invented for the project, to ensure that tolerances of +/-2 mm were maintained over the 65 m high façade.
Detail Specification and Testing
The masonry selected for the façade was carefully specified to ensure its long term behaviour and performance.
The brickwork underwent three rounds of testing. This extreme testing regime was carried out by James and Taylor to determine that this challenging brief could be effectively delivered. James & Taylor supplied the 40,000 bricks, 11,500 corbel fabrications and more than 3 million dowel and elastomeric components.
The specified bricks are 215 mm square and 69 mm high engineering bricks and have varying colours in order to be similar to the existing building.
The brick pattern is based on a Flemish bond, also similar to the existing building, with bricks stacked in pairs and prebonded with polymerised mortar, creating a block of 215 x 215 x 145 mm high, and the header bricks omitted, creating a ‘perforated’ screen of bricks.