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Question time: Mace delivers BBC Television Centre revamp

Stanhope’s multi-phased redevelopment of the former television centre has tasked Mace with retaining the site’s iconic question mark appearance.

Project: BBC Television Centre redevelopment
Client: Stanhope
Region: London
Construction manager: Mace
Architect: Allford Hall Monaghan Morris
Phase one value: c£400m
Phase one start date: April 2015
Phase one completion date: June 2018
Phase two value: c£300m
Phase two start date: 2018
Phase two completion date: 2021-22

Originally completed by Higgs and Hill in 1960, White City’s historic bastion of British broadcasting is now going through something of a metamorphosis. 

“The site was home to the BBC television centre that was built in the late 50s,” says Stanhope’s Forbes Macpherson who is responsible for delivery of the scheme.

“As a masterplan, it was a factory for television and it was built around the television studios in the centre – so the shape of the development seen from the air is that of a question mark. It was eight studios around a central hub that was for administration.”

Over time, other blocks were added towards the perimeter of the site with a car park and associated infrastructure. The straight leg of the question mark was added as further administrative space.

Stanhope bought the 5.5 ha site in 2012 and has split the scheme into two main phases. The first is under way and comprises the £400m mixed-use redevelopment of the central question mark and potentially an office building at the back of the question mark (see picture, below). The redevelopment is expected to include 432 homes across both phases (for more on phase two, see box).

annotated bbc studios

annotated bbc studios

The scheme was deep into phase one at the time of CN’s September visit with the £115m, 300,000 sq ft ‘plot A’ straight leg having been demolished and now well into its commercial rebuild.

“In the previous masterplan application we were looking to reuse and repurpose the existing structure to put offices into it,” Mr Macpherson says.

“But when we put a swimming pool on the roof, the structural gymnastics involved in the core to support it meant the building really didn’t work, so we took the old one down and put the new one up.”

Plot A also serves as a home for the combined heat and power energy centre, which went live in September and will service the structures delivered during both phases one and two.

“We took down the original [structure], which was actually two buildings and revealed the existing piles,” says Mace project director Adam Conyers. “Because we couldn’t be sure that all [our] piles would miss them, we had to bore out about 10, which was a fairly long-winded process.

“It’s something we’re up against more and more as we take down buildings,” he adds. 

Superficial craftmanship

The new plot A building features a reinforced concrete frame with post-tensioned concrete floors. But on the surface, one of the aspirations for architect Allford Hall Monaghan Morris was for the prominent use internally of high-quality exposed concrete finishes, including precast columns built by the Expanded Group division of Laing O’Rourke.

“While it looks like a single doughnut, and single doughnuts can be quite stable if they’ve got their cladding on, it was built as five segments”

Adam Conyers, Mace

Mr Conyers says the intention was to slipform or use precast as much as possible on the project to create these finishes using board marked concrete created by a rubber shutter from German firm Reckli.

This sees a mould created that bears the imprint of sawn timber, which can then be transferred onto a shutter liner, which in turn transfers the timber grain look during a pour.

The ‘board marked’ look is extensively used and highly visible in areas such as the lift lobbies and the atrium face. On the flip side, being an as-struck finish means there is very little opportunity for making good, since this would be glaringly obvious where it disrupted the timber look. 

Innovation above

“One of the interesting aspects of the scheme is that you can see quite a lot of the soffit,” Mr Conyers says. “It has one of the largest chilled plasterboard ceilings that we know of and that also has exposed sections of concrete, so the focus on high-quality concrete is extensive.”

Mr Macpherson adds: “The curing system is pretty innovative, it’s not been done at this scale before in the UK. It’s a steel and aluminium sheet with a plasterboard face panel so you have a descending cool.”

He describes what will be the eventual effect as being akin to walking into a church on a hot day. “Rather than being blasted with cold air you just get this feeling of embedded cool,” he says.

“There’s been two office buildings that we know of [using it] but not to this scale. It has the benefits of giving you increased floor-to-ceiling heights and energy efficiency.”

The doughnut

Work is also well advanced on the £100m centrepiece circular hub as well as the £130m outer ring of the question mark. At the end of this curl are studios one to three that are now back in the business of broadcasting with the BBC as the tenant.

There’s a certain irony in the site’s evolution that one of these – having reopened this summer – is now used to film The Jonathan Ross Show for broadcast on ITV1, after the presenter’s controversial departure of the BBC in 2010.

“The existing 1950s structure had to be removed to turn offices into apartments, which was elements of the core and bracing”

Forbes Macpherson, Stanhope

Moving clockwise all the way to the ‘straight leg’ of Plot A were studios four to eight that were demolished. With their basements deepened, they are well into their rebuilds that will provide more than 260 homes based around five separate cores.

“Sequence-wise we’ve had a series of handovers,” Mr Conyers says. “Plot B, the central helios building and the first [structural] core of plot C of the big curving building should have residents moving in before Christmas.” 

From cut and carve to rebuild

Activity-wise, plots B and C have gone through differing degrees of intervention.

Plot B is a ‘cut and carve’ structural re-engineering, with the studios of plot C having undergone a complete rebuild, albeit with all of phase one recreating the historic previous look of the site.

“Plot A looks remarkably similar even though it’s been completely rebuilt,” Mr Conyers says. “Plot B is actually the original building. We’ve re-clad most of the outside of it and extended the floorplate to create more space for some of the residential units,” referring to the outer circumference “stepping out” by about 2 m to facilitate this.

Phase two – sequence of events

Phase two is the tower to the left of the question mark, the large capital E-shaped building to the top and the silhouetted buildings further to the top that will be affordable housing (built on the footprint of the old car park), and finally 22 town houses further to the back of the question mark.

To build phase two concurrently with phase one would have been fairly demanding in terms of logistics, as the team has really only got two main entry points.

The phasings were done first of all from a construction logic point of view and secondly from a product perspective, as there’s a limit to how many apartments you want to build and then flood onto the market in one go.

“We’re progressing plans on phase two and have cleared the sites,” Mr Macpherson says. “We’ve demolished them so we’re ready to start and it’s likely we’ll start construction on phase two next year, just as construction begins to come to an end here so that there’s a seamless [continuation] of development.”

He says that while the intention is to build the capital E-shaped block and the tower consecutively, ultimately pacing and the programme for phase two will be based on by what Mr Macpherson refers to as “investor appetite”.

“Plot B was very demanding,” Mr Macpherson says. “The existing 1950s structure had to be removed to turn offices into apartments, which [meant] elements of the core and bracing. You couldn’t do that without putting in temporary bracing, otherwise the building would be unstable and you would potentially get some fairly catastrophic movements.”

Tight sequencing didn’t help matters either. “Unfortunately you have to move from one phase to the next in fairly close order,” he says. “So step one is to put in temporary bracing, then take out the old structure, put the new structure in, and lastly, take the temporary bracing out.” 

Fiendish geometrics

Mr Conyers explains a further complication. “While it looks like a single doughnut, and single doughnuts can be quite stable, particularly if they’ve got their cladding on, it was built as five segments. We didn’t have the calculations from that time and it was hard to understand how it had been analysed in those days.”

The stability measures go round the middle corridor of the building circumferentially. While these of course had to be straight to provide a brace, they were bracing against walls that are curving in what Mr Conyers describes as “a geometrical conundrum.”

stanhope mace bbc 7

stanhope mace bbc 7

It required some careful monitoring to check for untoward movements, but as work proceeded the permanent bracing went in according to plan, consisting mainly of steel-angled cross-sections placed into cross braces within bays of the building’s existing steel frame.

It hasn’t been straightforward, but work has progressed apace, meaning that Mace’s role on the job will complete with the final handover of phase one in June next year.

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