The expansion of Westfield London has included the construction of a huge, complex roof and a tricky connection made between the old and new buildings.
Project: Westfield London – phase two
Contract value: £600m
Main contractor: Westfield design & construction
Roofing subcontractor: Metal Yapi
Steelwork subcontractor: Severfield and William Hare
Start date: December 2015
Completion date: March 2018
Westfield London, the first shopping centre opened by the then Westfield Group in the UK in 2008, was a substantial project to bring to fruition.
It took five years to build at a cost of £1.6bn, with Westfield carrying out the work through its in-house design and construction arm. Now, nine years after the centre first opened, the site is once again home to a large construction scheme – the biggest of its kind under way in Europe.
Set to open in March 2018, the £600m expansion of Westfield London will create 740,000 sq ft of additional retail, dining, entertainment and leisure space, bringing the total gross leasable area up to 2.6 m sq ft across the entire development.
The new build comprises three main components: the retail extension; an adjacent building to house restaurants and bars; and an office on top. The extension features a steel frame, with different parts of the project being carried out by two different subcontractors: William Hare and Severfield.
“I’m a great advocate of steel in the right place – and in a shopping centre, it’s absolutely right to do it [that way],” explains Westfield UK head of design and construction Keith Whitmore. “You can change concrete, but changing steel is so much easier – it’s much more flexible. It’s paramount to think about what might come down the track.”
One of the first elements of the scheme saw the team move a bus layover from the Dimco Buildings, the red-brick building that was used as a filming location for the Acme Factory in Who Framed Roger Rabbit? A new bus station was built around that structure when the first phase of Westfield London opened in 2008, with the bus layover now moved into a new concrete structure.
“Across Westfield London, Stratford City and Croydon, we have the potential to deliver circa 4,000 apartments, which puts us in the upper echelons of British residential developers”
Keith Whitmore, Westfield
“On phase one we did a similar exercise with the trains,” Mr Whitmore says. “Beneath where we are is a stabling yard for 16 Central line trains. We built that as a concrete box in the ground.” The Central line has also dictated the location of the new mall, with the tunnels influencing where the foundations could go.
Westfield handed over the 32 bus-capacity layover in September 2016 – and built the structure in such a way that its roof can act as a podium for a new residential development. This residential element is a new step for Westfield in the UK, with 90 affordable units currently under construction and planning permission in place for a further 1,100 once the retail expansion completes.
“It’s a relatively new venture for Westfield here in the UK, although they’ve got a much bigger portfolio [of residential] in the US,” Mr Whitmore says. “Across Westfield London, Stratford City and Croydon, we have the potential to deliver circa 4,000 apartments, which puts us in the upper echelons of British residential developers. At the moment we’re not doing it in joint venture – it’s all Westfield.”
In total, Westfield says this scheme will end up with 162 affordable housing units, with the potential to rise to 250 if it generates a “significant surplus”.
One of the most significant challenges of phase two has been the 40,900 sq ft roof – a freeform structure that is “the biggest of its kind in the world”, according to Mr Whitmore.
The original roof for phase one, constructed in 2008, featured a mixture of solid and glazed panels, framed in an undulating triangulated structural steel frame. “Today, technology has moved on so much that we can now produce a fully glazed design and the result is this stunning and sustainable freeform structure, which takes the roof seamlessly across the new extension,” Mr Whitmore says.
Westfield London expansion Westfields Roof external
The design of the single-layer steel and glass roof is a first for the UK, Mr Whitmore claims, and only the second of its type in the world. “We designed the steelwork to support mobile gantries that we could use to install the roof,” he says.
It weighs in at 197.5 tonnes, and comprises 1,429 environmentally friendly glazing units and 281 aluminium panels. The structure also contains 874 bespoke nodes that connect these units, each individually sculpted using a five-axis computer numerical control (CNC) milling machine. No two nodes are identical, with each having a dedicated position in the design.
Turkish specialist contractor Metal Yapi has installed the roof, in its first project for Westfield. Its structure is designed to connect seamlessly to the existing roof – and it’s the connection to the existing building that has presented the construction team with another challenge.
“We cut the side of the core, then threaded in the steelwork to support the core above”
Keith Whitmore, Westfield
Our site tour takes us to the ‘break-through’ area, where the new building has been stitched onto the old. Rather inconveniently, this area was previously home to a concrete stair and lift core, which the team has had to remove to gain access. It hasn’t disappeared completely, though. Instead, 60 tonnes of steel has been installed to support the top half of the core, with the complex’s Vue cinema sitting around it, while the bottom half was removed to make way for the connection between the malls.
“We cut the side of the core, then threaded in the steelwork to support the core above,” Mr Whitmore says, pointing to the huge steel beams that now sit overhead. Retailers located around the core had to be moved to other parts of the existing mall before work could begin.
The scheme is also notable for its extensive use of technology.
It’s the first Westfield project to take full advantage of building information modelling. “Our biggest step-change in how we operate is that we’ve embraced BIM – we did do that on Stratford City, but only to the old stage C, which is effectively concept and planning,” Mr Whitmore says.
Westfield London expansion Night View
“But on this project and [the previously completed] Kidzania, we made a decision that we’d deliver it in BIM and that we’d take it as far as possible, focusing on the main packages.”
Westfield has taken it so far that it has even re-written the BIM Protocol – the supplementary legal agreement that is incorporated into construction contracts – to make it better suit its own needs. BIM is now set to be rolled out on its pipeline of schemes: phase two of the Stratford City development, and new shopping centres in Croydon and Milan.
“Our biggest step-change in how we operate is that we’ve embraced BIM – we did do that on Stratford City, but only to the old stage C, which is effectively concept and planning”
Keith Whitmore, Westfield
The team has also worked hard to make sure its data is robust and accurate to get the most out of BIM, working with an external consultancy to validate it and make sure that consultants and trade contractors are achieving the required levels of data accuracy. “The quality of the supply chain in terms of selection is quite important. It’s more than the old-fashioned tender – you have to ask the right questions to get the right answers,” Mr Whitmore explains.
Westfield has made use of drones on the project (see video), conducting more than 100 flights over 12 months and producing 3D digital point-cloud surveys. The team has done this every two weeks to help with site briefings and inductions – as well as using this to plan work and track progress. “We can use it as a management tool – to see who did what, when,” Mr Whitmore says.
The team’s laser scanner meanwhile captures one million points per second and translates them into a cloud mesh, and then into a 3D BIM model. It is accurate to 3 mm either way and produces a virtual walkthrough, which has proved useful during the build phase. For example, Westfield’s retail delivery and leasing teams have been able to show prospective tenants exactly where their new shops will be located and what context they sit in.
The project is progressing “pretty much” to schedule, Mr Whitmore says, and will be ready for opening in March. A major target was hit when the 230,000 sq ft flagship John Lewis store was handed over to the retailer in July, ready for a 36-week fit-out process to begin.
Westfield London expansion John Lewis Building
“This represented a significant milestone for us in the construction phase,” Mr Whitmore says. “And getting the early agreement with John Lewis had also represented a key moment – it was really the trigger to the commencement of the development concept stage into the physical.”
Other retailers have continued to come on board, with the expansion set to create an additional 8,000 permanent jobs for the White City area. The project itself has been no slouch in that regard either, with 4,420 workers on site to date.
Europe’s largest retail construction project continues to inch its way towards completion, adding further to the transformation of this part of west London.
As well as the huge extension to Westfield London, the retail group has a busy pipeline of work coming to market soon.
Stratford City, the major development on the edge of the Queen Elizabeth Olympic Park, is set to get its own phase two extension, with the scheme at stage two design. There, the extension will go downwards, with the centre futureproofed for future expansion when originally built. “There’s an aspiration to get on site towards the end of this year, but that will depend on approvals,” Mr Whitmore says.
Westfield has another site at Stratford that will eventually be home to a commercial office building on Westfield Avenue, directly opposite Lendlease’s International Quarter development. That scheme is also still in design, with Westfield in negotiations with a tenant for a pre-let.
The residential element at Stratford – around 1,400 homes – has outline planning permission.
Further afield, the firm’s Milan development is progressing apace, with demolition and site clearance completed and commencement on construction set to begin in Q1 2018.
Closer to home, its scheme in Croydon is still in the planning process, with timings for construction still up in the air while a final decision is made.