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King’s Cross Central, the huge regeneration project that stretches north of the station, has been a testbed for sustainable office development for some time – certainly since Bennetts Associates’ headquarters for Camden Council on Pancras Square became the UK’s first BREEAM Outstanding workplace in 2014.

Now the same architect has added another BREEAM Outstanding commercial building to the estate: a UK headquarters for Meta, owner of Facebook. There are elements in common between the two projects, not least the flexible floorplates, dramatic central atrium and expanses of exposed in-situ concrete frame. But the Meta HQ also shows how thinking about sustainable design and construction has evolved in the intervening years, particularly with regards to embodied carbon. 

The first thing to note about the Meta HQ is its sheer size. By far the largest completed office building at King’s Cross Central, it varies between 10 and 12 storeys and, at 180m, is as long as the Gherkin is tall. Even its address stretches from 11-21 Canal Reach. “It has the floor area and more of a skyscraper, but lying on its side,” says Simon Banfield, director at Ramboll, the structural engineer on the project.

The building’s unusual “groundscraper” form flanks the rail tracks out of St Pancras, and is expressed as four connected volumes that kink like train carriages turning a corner. This vast footprint accommodates more than 4,000 employees on 37,000m2 of large, open floorplates. Above it all, the roof has enough space for a 3,900m2 park, complete with trees and beds of wildflowers. 

What it doesn’t have is a basement. This was an early decision, as the scale of the site meant that sufficient floor space could be provided without one. “This sounds quite simple, but it makes a huge difference,” says Banfield. Plant has instead been mainly housed at the back of the building, facing the rail tracks and the neighbouring district energy centre, which also helped to keep the rooftop free for landscaping. 

This was partly the result of a design process in which – unusually for a scheme that began life back in 2015 – embodied carbon was measured and monitored from the outset. “It was before everyone became carbon literate,” says Banfield, “but [developer] Argent wanted to push it forward. It is a pretty early project to be completed with an embodied carbon story.”

The project undertook embodied carbon assessments from Stage 2 to completion, with a final as-built upfront total of 705kgCO2e/m2 – about 25% lower than a “current average design” for a speculative office of the same scale, estimated to be about 950kgCO2eq/m2 by the LETI embodied carbon rating system. According to calculations by Bennetts, the material-efficient design saved 10,564 tonnes of CO2.  

Much of this comes down to the structure. In order to improve the flexibility of the workspace, Argent requested long spans, so it is based on a large, regular grid of 13.5m x 9m in the eastern section of the building, reducing to 9m x 9m at the western end. Spans above 9m would usually require deeper slabs, but the use of post-tensioning has allowed depths to be limited to 350mm on the 13.5m grid and 250mm on the 9m grid. This, Banfield suggests, has lowered the amount of concrete needed by 20-25%, as well as minimising the need for reinforcement.  

Long spans and flexible spaces reflected the priorities of the commercial market at the time, as well as the fact that this was a speculative development. But they also serve to future-proof it against the shifting sands of a rapidly changing society – particularly relevant with a design life of 100 years. Banfield notes that before Meta came on board, there was a hiatus during which Ramboll explored the possibility of adapting the structure to become a life sciences centre. “We did an assessment, and the concrete spaces worked pretty well,” he says.  

On the other hand, post-tensioned concrete is rarely held up as the most adaptable of structural materials, due to the difficulty of opening up slabs without cutting through the tendons. Ramboll and Bennetts have sought to sidestep this by including a number of non-structural “soft spots” in the frame, primarily in the knuckle joints between the four main volumes.  

Throughout the structure, cement was replaced by 30-70% GGBS. Banfield points out that the low-rise linear form made a higher proportion more viable: “GGBS affects curing times, so formwork needs to be left in place for longer. If this was a skyscraper with a small footprint, the contractor would be desperate to strike it as quickly as possible to maintain the floor-to-floor cycle. But here, because the floorplates are so large and you’re not always rushing on to the next one, there is less pressure on the programme.”  

The GGBS has also lightened the tone of the concrete, which has been largely left exposed – another requirement set down by Argent at the project’s inception. “One of the carbon savings was to make the concrete the finish,” says Banfield. “It was schemed entirely without ceilings, the staircases aren't lined, the floors are exposed. The quality of the concrete allowed us to do that.” Ply-faced metal formwork was used throughout the building, leaving a controlled matt finish. 

Meta’s interior fit-out, designed by Gehry Associates, has added a layer of busyness to the pure concrete aesthetic, with timber-clad pods, pop art and thickets of indoor plants giving it a suitably big tech atmosphere. It looks like the sort of place where the fabled “metaverse” might indeed take shape. Whatever that virtual future may hold, it’s reassuring to know that so much care has gone into minimising its very physical impact on the fragile world around us. 

Project Team


Bennetts Associates 

Structural engineer

Ramboll, BAM 

Services engineer


Sustainability consultant

Sturgis Carbon Profiling 

Main contractor

BAM Construction 

Photos Matt Livey © Meta, Hufton + Crow, John Sturrock, Will Pryce