It’s lights, camera, construction at a new TV and film production centre that promises to be the most environmentally friendly in the world. Paul Thompson reports

Scheme: Sky Studios Elstree Client: Legal & General Main contractor: Bam Construct Contract value: £192m Contract type: two-stage Design and Build Project start: November 2020 Project completion: Summer 2022

The town of Borehamwood sits in London’s commuter belt to the north-west of the capital. At first glance, you could hardly imagine a less likely location to rival Los Angeles’s Hollywood as a worldwide centre of film production. Yet this unpretentious corner of Hertfordshire, with its sprawling post-war housing estates and mid-1980s leisure centres, has done just that over many years.

Some of the biggest names in film and television have walked its streets while contributing to a film and TV production highlights reel that includes some of the biggest-grossing box-office hits in history. Star Wars, Indiana Jones, The Dam Busters, Ice Cold in Alex, Quadrophenia, EastEnders and Big Brother all have their roots in Borehamwood.

Now production giant Sky is set to underline the area’s impact on the world of entertainment with the development of a vast complex situated on a brownfield site at the eastern edge of the town.

Main contractor Bam Construct is heading the cast list under a £192m deal that will see 13 sound stages built, as well as allied offices and set-storage facilities at the Sky Studios Elstree development for client Legal & General.

Streaming services such as Netflix and Amazon Prime have helped to boost the UK’s TV production sector to achieve record revenues in recent years, according to industry body PACT. Its success has prompted a rush for more filming space.

Plans have been submitted for a 1 million square feet studio with Hertsmere Borough Council, next door to the Sky project. Bidwells put in the application in April for the 90-acre site, to be called Hertswood Studios.

On the other side of Hertfordshire, Sunset Studios has announced plans to build a 91-acre facility at Waltham Cross, its first studio lot outside the US.

Last December, Laing O’Rourke started on site to deliver a studio project at the former Littlewoods headquarters in Liverpool. That same week, the University of Reading signed a deal to build a £200m film studio at its science park campus in Berkshire.

Barking and Dagenham Council agreed a deal with Los Angeles investor Hackman Capital Partners last year to fund a studio build that will be called Eastbrook Studios London. Meanwhile, nearby Enfield Council opened new film facility on the site of its £6bn Meridian Water residential development earlier this year.

Paul Avery has landed the role of leading man for the project’s delivery. As construction manager for Bam Construct, he has watched over the scheme since its start date in November 2020, and is due to oversee the project until its completion in summer 2022.

“This is an 11-hectare site with 13 sound stages, two production-support storage warehouses, office accommodation, a dedicated reception and office building, as well as a multi-storey car park, water-attenuation ponds to dig and sustainable drainage systems to install,” he says. “There is plenty to get done.”

After inheriting a sloping brownfield site at the start of the project, the team has balanced its 2-3 metre north-to-south fall through a 56,000 cubic metre cut-and-fill regime. This has seen material reused within the project’s boundaries – first cut from the north end of the site, and then placed and compacted in-situ toward the site’s southern boundary. The team has used vibro stone column compaction techniques to help stabilise and consolidate the ground across the site (see box, below).

Other than the car park which features steel columns encased in concrete and concrete floor slabs all of the buildings are simple steel frames. Their relative light weight, coupled with the bearing quality of both the natural ground at the site’s northern end and the newly consolidated fill at the south, has meant the team has been able to avoid a site-wide piling exercise.

Instead, specialist Aarsleff Ground Engineering used a localised array of 300mm square-section precast concrete piles beneath the car park. Around 350 have been driven to depths of 14 metres into the London Clay bearing strata in total. The rest of the buildings are founded on ground-bearing reinforced concrete pad foundations, generally around a metre deep, but with localised steps and recesses.

Thanks to the lightweight nature of the bulk of the buildings across the site and the relative stability of the underlying ground conditions, the team opted to consolidate the site using vibro stone columns rather than install extensive piling.

This technique improves weak soils or fill by installing densely compacted columns of gravel using a vibrating compaction head. This gravel column reinforces all soils in the zone and improves the density of the surrounding ground. “There have been hundreds of columns installed,” says Avery. “The bulk are across the southern side of the site where we have the bulk of the fill. They have been placed at 1 metre centres to depths of 4 metres or more.”

Along the site’s eastern periphery, a steel sheet pile wall has been installed to depths of 6 metres, with up to 2.5 metres above ground. This provides a barrier between the site and the two water attenuation ponds that, alongside the vast array of sustainable urban drainage systems and water attenuation tanks buried within the confines of the site, will hold surface water run-off before discharging it slowly to the mains drainage system.

The initial plan for the car park was to use continuous flight auger piles, boring and pouring concrete in one operation. “But that meant we would have had to deal with the arisings,” Avery says. “Using precast piles has reduced the amount of muck away and reduced costs. The steel buildings are huge – but, really, in engineering terms, just big boxes of air. The frames are relatively light in weight, which is why pad foundations are adequate.”

As light as the steel frames might be, they are enormous – almost 58,000 pieces with a total weight of 6,500 tonnes. In the sound-stage buildings, huge 4-metre-deep steel trusses will span 50 metres across the buildings to form the roof and allow gantry access for production and maintenance engineers when the buildings are in operation.

These huge trusses have been brought onto site in three sections, lifted and bolted together before being hoisted into position using three mobile cranes. Each hoisted one truss per day. At the peak of the work, steelwork fabricator Severfield had nine mobile cranes on site.

“We have worked with Severfield on several major projects,” Avery notes. “The installation of the precast concrete lift-shafts and cores in buildings around the site was also part of the steelwork package. The sections were precast by Creagh Concrete and installed at the same time as the steel frames were going up. It makes it all more convenient.”

In the sound-stage buildings, the reinforced concrete-slab floors have been poured to an extremely high specification. Moving cameras are stubbornly efficient at revealing even the slightest undulation across a concrete slab surface, which is why the team is using a laser-controlled concrete-levelling machine to hit the tolerance target, rather than self-levelling concrete and a screed surface later. A vibrating float draws batches of concrete across the slab bay, levelling and consolidating the concrete in a single pass. The concrete itself is a standard high-strength mixture rather than a specification mixed specifically for the project.

“We needed the surface to be both robust and level,” Avery says. “It was felt that a screed could pose additional, unnecessary maintenance issues. It is a standard concrete mix that we can source easily from any of the four suppliers we are using. We can be pouring 150 cubic metres per day for the sound-stage slab pours.”

With the first call of “lights, camera, action!” due to be heard within a year, the team is ready to push on with the huge volume of work that remains. This includes the delivery of the 900-space car park, which has been subcontracted out to Watford-based car parking design-and-build specialist Huber, and the Cat B fit-out of the office buildings.

For now the key role is to stay on script, finish the job, and make way for the stars.

Billed as the ‘most sustainable film and TV studios in the world’, the new Sky Studios will include a host of features that will help the team to deliver on that promise and hit its BREEAM Excellent target.

Although there are 14,400 square metres of photovoltaic cells across the project, which will help to offset some of the energy demands from the completed scheme, much of the sustainability measures are founded around the acoustic and air-leakage requirements of the buildings.

High performance in these areas is fundamental for TV and film production – no one wants the drone of an aircraft passing overhead to ruin a take on a costume drama – but they are also vital in making the buildings as energy-efficient as possible.

The walls are constructed using a cladding system with a total build-up of 750mm thickness. On the outside of the steel frame is a beefed-up traditional two-layer system with outer cladding, a 250mm-thick layer of insulation and a liner system. The cladding on the inside of the steel frame is similarly built up with insulation and cement particle board. Where internal walls divide the sound stages, the design team has developed a detail that breaks the floor slab directly beneath. The slabs are cast into bays with each bay at the internal-wall gridline sitting 25mm off one another. This enables the team to fill the gap with flexible soundproofing material before installing the internal acoustic wall directly above.

“They are acoustically independent slabs,” Avery says. “It means there is no chance of any sound flanking between the sound stages.”

Note: this article was amended on 23 September to clarify the material used for the car park.