The refurbished Bankside Power Station became an instant icon of both the art world and the architectural profession when it opened its doors as the Tate Modern in 2000. The new extension to the gallery that opened in summer 2016 may not have the industrial pedigree of the original, but it is no less striking or prestigious in its design. Russell Drury takes a detailed look at the installation of flexible cable management within the concrete pour by REL, during construction of the Tate Modern’s new extension.
Located to the south of the existing gallery, Tate 2 was designed by globally renowned architectural practice Herzog & de Meuron and its twisted pyramid concrete structure rises 10 storeys high, matching the height of the former power station’s towers.
The building is not only designed to provide a backdrop for the artworks within, but to reflect Tate Modern’s global standing as a curator of modern art. While the new structure is very different from the Orwellian grandeur of the existing building, there is a synergy in the bare concrete finishes that characterise the interior of both.
When it came to installing the cable management for the single core that rises through the centre of the Tate Modern extension, this focus on bare concrete walls presented significant challenges. Consequently, the requirement for flush mounted electrical accessories demanded an in-situ cable containment solution with minimal exposed service box lids within these areas.
The previous installation phases for the building used the traditional in-situ galvanised conduit method, but REL immediately identified this method as being costly and, more importantly, unworkable.
REL’s solution was to install Marshall Tufflex’s ‘Supertube’ on a floor-by-floor basis as the building was constructed, with the installation on each floor carried out prior to each stage of the concrete pour.
The core rises up all 10 storeys of the building and includes staircases, passenger lifts and a goods lift. The requisite flush cable management infrastructure needed to accommodate a wide variety of cabling including power, lighting, data, fire alarm, security, access control and CCTV, creating dedicated networks comprising around 4.2km of conduit in total and 2,000 back boxes and fittings.
Supertube provides a robust cable management solution as it is pliable and durable in its construction and allows up to 30m runs between service junctions, greatly reducing installation time. The conduit construction is polyethylene internal and external layers sandwiching and sealing a welded aluminium tube within.
“The architectural vision for polished concrete walls with an industrialised finish meant that there would be no available voids for cable concealment within the core floors, walls or ceilings,” explains Steve Jamieson from REL. “From the outset of the building services design, it was clear that an innovative approach was essential as was early collaboration between the design and installation teams to ensure a successful outcome.”
With early engagement so critical to the cable management installation, the installation for this area of the building was contracted as a separate package of works, outside of the main £20m electrical installation, which was carried out following structural completion.
Steve continues: “Our client was the concrete formwork contractor, Byrne Group, with whom we had previously worked with successfully on the 2012 Olympic Village. The installation was carried out as part of the concrete formwork.
“It required close cooperation with the contractor, architect and building services consultant to ensure that accurate working drawings were prepared as no changes could be made once the concrete pour for each floor had begun.”
Although the installation took a total of 18 months to complete, just 6,000 man hours were required on site.
Steve explains: “There was an intensive design phase prior to any work taking place on site and then we were typically on site for a three week period, installing the cable management ready for the next pour. We’d then stand down while Byrne Brothers prepared the next level and be called back to site to continue the installation.
“The work was scheduled according to programme but we had to be flexible and ensure we were ready to begin each phase of the installation in line with the progress of the build.”
Steve continues: “As with all UK construction projects of this nature, inclement weather is an occupational hazard. As a result, to maintain the construction programme, the formwork operation had to be accelerated at various points to overcome the delays caused by the weather. As a contractor based close to the site, we could respond quickly and efficiently.”
The layout for the cable management was designed in 2D by the consultant in accordance with BIM level 1 and developed by REL’s design manager. A web based central portal was used for efficient collaboration across the team.
While flexibility is important for the gallery spaces, which may need to be reconfigured for new exhibitions, the core has been designed for purpose. There is no intended scope for change or future additions, so the cable management installed in the core was designed to consider the service life of the building. While the layout will not be adjustable, the system does allow for full system rewiring.
Steve explains: “The Supertube’s smooth inner surface allows cables to be inserted using a traditional draw wire, enabling cable pulls of up to 50m in length through a tube with no fittings. This minimises the risk of any cables snagging during the build or any future electrical refurbishment, which would not have been possible using a traditional galvanised conduit and fittings arrangement.”
During each stage of the core build, the cable management was measured, fabricated on the level deck, manhandled into position and guided within the steel rebar in accordance with the working drawings.
The installation team could use the local scaffolding platforms erected within the main structure to minimise any working at height requirements and the need for any lifting equipment.
Feeding the cable management through the rebar network remained a challenging process, however, because the steel bars were so closely positioned in some areas that it was difficult for installers’ hands to fit through to position the tube.
“Only a flexible cable management solution like Supertube could have been used to deliver this installation as it allowed the team to bend lengths of conduit to fit into position around the steelwork and maximised the lengths we could use without a termination,” Steve explains. “We allowed an excess of around 2m on each length of conduit to protrude beyond the concrete pour level, so that we could simply connect the next sections to the existing installation after each concrete pour had cured.”
The constricted site conditions meant that a maximum of just four REL installers worked on the job at any one time, with the same site manager and technician working on the scheme consistently across the 18 month delivery period and an additional two electrical installers available for additional resource as required.
Each length of installed conduit was secured to the steel rebar with cable ties to hold it firmly in position during the concrete pour, and the installation was signed-off by the design team prior to the pour.
An immersion vibrator was used to assist in the spread of the pour within the shutter and close attention was paid to the conduit locations to ensure no damage occurred during the pouring process. The REL team also had to ensure that no moisture from the concrete pour could penetrate the conduit.
Steve says: “Multiple layers of insulation tape were applied to each conduit connection over a 50mm width each side of the connection to ensure moisture resistance. Other proprietary tapes were found to be less effective due to less adhesive qualities. Plastic fittings were used for the connection process which were beneficial compared with their metal counterparts as they were a better fit and the solvent cement used for the joint provided additional moisture resistance.
“Although we were confident about the integrity of these conduit joints during the pour, it was inevitable that moisture would get into the accessory boxes. Attempts on previous construction phases to seal the boxes with intumescent foam had not been successful so an alternative solution was required. A high grade foam pad was cut to size and then inserted into the box. The entire box was then wrapped in insulation tape to provide further sealing. Each box pad fascia was then colour coded by service for easy future identification.”
As the next level of rebar cage was added, REL was present to ensure the existing exposed conduits for that level were not damaged. This means that no element of the cable management installation was damaged during the construction process.
Steve concludes: “This was the first installation of this kind we had ever been contracted to carry out and it may be a while before we work on another installation process of this type or such an iconic building again.
“We not only learned a lot about alternative approaches to cable management installation but we realised how valuable a flexible approach can be and the importance of interdisciplinary collaboration in addressing complex project challenges, both at design stage and through active engagement on site.”