Tate Modern Gallery's Ultra-Futuristic Extension - page 6 of 6
Construction of the brick façade is as unique as the structure, with the bricks being used in a way never previously thought possible and acting as a veil over the structure.
As the facade is far from vertical, the usual bricklaying techniques were not possible, and mortar connections could not be used as the brick overlaps are too small.
The team developed the idea of pre-assembling pairs of bricks into blocks. The blocks loosely bear on one another through neoprene washers held in position with vertical stainless steel pins inserted through pre-drilled holes.
Stainless steel bosses cantilever from the concrete frame to provide intermittent support for the brickwork.
This method has created a flexible facade, disassociating movements in the brickwork from the frame, effectively allowing the rain screen to act as a big heavy overcoat
On site the blocks were connected together using elastomeric joints, stainless steel pins and a resin joint. The façade works in a series of arches to allow the brickwork to move horizontally and vertically and is restrained back to the façade with 11,500 corbels made up of 400 types.
Corbels are an integral part of the scheme.
Supported by the internal perimeter structure and floor beams, precast panels provide support for the corbels and brickwork and provide a thermal and moisture barrier to the building.
Sitting in empty header spots in the masonry, the corbels support the brickwork skin and offer a mechanism for reducing general frame tolerances as an interface to the more refined brickwork.
Solid brickwork is used on the lower levels. The sloping brickwork is achieved by offsetting blocks at each course to create the correct overall slope. In the vertical façades the double courses are also offset in and out of the wall plane to give a texture similar to the sloped façades.
There are 5 distinct ‘types’ of brickwork:
- Vertical perforated – stepped brick
- Sloping perforated – stepped brick
- Sloping solid – flush brick
- Vertical solid – flush brick
- Vertical solid – stepped brick
At the corners and creases additional ‘special’ blocks and site cut standard size blocks were required to suit the interface between adjoining brick elevations. A procedure was developed to maintain a consistent method of support to the brickwork and to also meet the required irregular visual appearance.
Grade ‘A’ Concrete Finish Essential
Having been awarded the contract to extend the basement of the landmark Tate Modern gallery on the south bank of the Thames river, McGee Construction required a formwork and falsework solution that could be used in the very tight confines of the site.
Due to the challenging design of the extension, which required a Grade A concrete finish, due to the concrete work remaining exposed after completion, McGee Construction put the design and supply out to competitive tender, with RMD Kwikform awarded the project.
RMD Kwikform’s southern region general manager, Neil Thomas spoke about the project challenges,:
The formwork and falsework for the project represented the first phase of the construction of an extension to the Tate Modern Gallery. Unlike standard basement extensions this also involved the redevelopment of three old oil tanks, stored in the ground.
A lot of the attractive concrete features involved in this project were peculiar rigging shore columns, constructed at various angles, so the light deflects at different degrees and casts shapes across the floor.
In addition to the formwork challenge, the RMD Kwikform project team had to work closely with McGee to overcome the logistical issues onsite. With a central London location and limited space, just in time deliveries had to be scheduled and the design team had to visit the site in order to determine how to design a workable solution.
To achieve the high quality finish, RMD Kwikform incorporated the ply layout within the falsework design, which proved very challenging. The end result is one that will impress visitors walking from the existing to the new extension, with an almost marble effect finish achieved between the old concrete and the new.