2 Finsbury Avenue: How sustainability reshaped McAlpine’s latest City landmark

Sir Robert McAlpine is no stranger to ambitious City of London projects.

Yet few have been so fundamentally reshaped by sustainability as 2 Finsbury Avenue (2FA), which has undergone major changes to its design, engineering and construction since the project’s conception seven years ago.

Rising 170m above Broadgate, this is McAlpine’s sixth project delivered under a long-running framework agreement with British Land. The £701m development comprises a 38-storey east tower, a 24-storey west tower linked by a 13-storey podium and winter garden, providing around 1,100,000 sq ft of mixed-use space.

Due for completion in June 2027, the scheme is targeting BREEAM Outstanding, WELL Platinum, EPC A and NABERS 5-Star ratings. It has been designed as an all-electric building, incorporates extensive material reuse and passporting strategies, and uses electric arc furnace steel for the vast majority of its superstructure.

McAlpine project director George Amy has been involved with 2FA since June 2019, joining the project during RIBA Stage 1.

“Sustainability was really coming to the fore at that time, and British Land recognised it would be even higher on the agenda when the project completed in 2027,” Amy says. “That became one of the key drivers shaping the building design.”

One of the clearest examples of this is the superstructure.

Sir Robert McAlpine worked with steelwork contractor William Hare to incorporate 95% XCarb steel manufactured by electric arc furnace using recycled steel and renewable electricity. The contractor says this is expected to save around 5,000 tonnes of CO₂e compared with conventional blast furnace steel.

However, this did mean design and engineering changes, and not just to the structure.

“This is my sixth tower in London,” Amy explains. “Previous towers I’d worked on used deep plate girders that provided highly efficient long spans. At the time we were planning this project, those sections could only be produced from plate steel manufactured in blast oxygen furnaces. However, electric arc furnaces, which use recycled steel, could only produce standard universal beams and columns.

“That decision drove the structural design. In a typical office tower, ventilation ductwork can be routed through openings in the webs of deep structural beams. But because we opted to use electric arc furnace steel sections, we were working with shallower, heavier universal beams that could not accommodate the same services strategy.

“As a result, both the structural and MEP designs changed. Instead of a typical 150mm raised floor, we adopted a 300mm raised floor and moved the air-distribution system beneath the floor.”

To ensure the project’s sustainability claims were robust, team members travelled to ArcelorMittal’s Luxembourg facilities to verify manufacturing processes and renewable energy credentials.

The same scrutiny was applied to other packages, including the aluminium facade, which has a distinctive, sawtooth profile. When one company’s recycled-content claims failed to meet requirements, the team switched suppliers.

2FA’s sustainability strategy extends to future reuse.

The project uses the Madaster platform to create a digital record of building materials, allowing future owners to identify, recover and potentially reuse components when the building reaches the end of its operational life.

“British Land wanted every component in the building digitally recorded so that, should the building be re-purposed in the future, the building materials could potentially be reused elsewhere,” Amy explains.

“We worked with Ramboll, William Hare and AJ Morrisroe on how to make future disassembly of the decking and slabs more straightforward. In conventional composite construction, metal decking and concrete slabs are connected to steel beams using welded shear studs, which makes it difficult to recover the structural steel without damaging it at the end of a building’s life.

“We developed a system using sacrificial plates bolted to the beam flanges. The floor slab could then be connected to these plates rather than directly to the beams. When the building comes to be disassembled, the bolts can be removed and the beams separated from the slab without damaging the steel, making reuse much more feasible.”

McAlpine also worked closely with William Hare to develop greener metal decking.

“Usually, William Hare would get their decking from Richard Lees, who sourced the steel coil from Tata,” explains Amy, “but Tata didn’t supply electric arc furnace coil. So, instead we went to ArcelorMittal, who were able to supply steel coil from their electric arc furnace to Richard Lees to profile for William Hare.

“That gave us a major carbon saving and produced a lighter deck, which also helped with manual handling and health and safety on site.

Work on 2FA began in July 2022 with the soft strip and deconstruction of two existing 10-storey buildings on the site.

“We worked with GXN, British Land’s sustainability consultant, prior to demolition to identify which materials had reuse potential and recover as much as possible,” Amy says.

Around 25 tonnes of structural steel beams were extracted, cleaned, tested and warrantied for reuse. Additionally, some 2,500m³ of concrete was crushed and reused within the foundations, while 9,500m² of raised access flooring was removed and stored for future reuse.

McAlpine also incorporated around 100 tonnes of steel from the existing structures in the new development and repurposed much of the original aluminium facade as cladding for the new cycle ramp.

The project team has sought carbon reductions throughout the design and construction process.

McAlpine worked with piling contractor Cementation Foundations Skanska to rationalise the foundation design, reducing pile diameter from 2.4m to 1.8m. More electric arc furnace steel was used for around a third of the plunge column piles, which cut embodied carbon by 15%.

Also during the piling works, McAlpine pioneered the use of basalt reinforcement within guide walls. Manufactured from volcanic rock, it is significantly lighter than conventional steel reinforcement and McAlpine says it can reduce embodied carbon by up to 60%.

The facade contributes significantly to the building’s sustainability. Manufactured using aluminium produced with renewable energy, it is expected to save approximately 1,900 tonnes of CO₂e compared with a conventional product, according to McAlpine.

At final design stage, embodied carbon was reduced from 755kg CO₂e/m² to 656kg CO₂e/m². According to Amy, subsequent optimisation has lowered the figure further to around 647kg CO₂e/m².

“Considering the design originated in 2019, achieving those figures is quite an achievement,” Amy adds. “A lot of credit should go to my sustainability manager Kathryn Castledine.”

Delivering a 170m tower development in the City always means significant construction methodology considerations.

The ground engineering required installation of 280 secant piles and 78 bearing piles extending up to 60m below ground level. Additionally, the project involved construction of three basement levels.

Looking for programme savings and logistical efficiencies, McAlpine opted for a top-down construction methodology.

“We wanted to get the superstructure started as quickly as possible, so we designed the plunge columns – 60 in total – in a way that allowed us to maximise the freestanding height of the cores,” Amy says.

The approach also involved constructing the first basement slab early and using it as a permanent horizontal prop.

“Instead of large temporary steel propping systems in the basement, we used the B1 slab as a horizontal prop and excavated straight down to B3 while simultaneously building upwards,” says Amy.

The strategy allowed excavation and superstructure construction to proceed concurrently. While the towers rose above street level, below ground excavation work proceeded, removing approximately 36,500m³ of material to create the basement structure.

According to McAlpine, the approach removed around nine months from the programme.

Building safety has been another major consideration for the project as regulations continue to evolve post Grenfell, says Amy.

“For example, suppliers withdrew warranties on some drylining systems which previously could be used for smoke shafts, which meant redesigning to come up with another solution using sealed blockwork instead, and that required its own testing,” he explains.

Digital tools have supported design and construction since the early stages of the project.

“The project has been modelled since approximately Stage 3 and we employ two dedicated BIM engineers,” says Amy. “We use a Dalux 3D viewer for all the whole team to view the model ‘on the go’, plus Buildots to capture images and compare site progress against programme and identify quality issues. The 4D programming software we use is Synchro.”

Managing logistics on a constrained City site has required detailed planning.

The project occupies a unique location at the intersection of three local authority boundaries. While the site sits within the City of London, neighbouring streets fall within both Hackney and Islington, meaning major lifting operations often require engagement with multiple authorities.

To maximise use of space, the tower crane is supported by a steel grillage cantilevered from the east tower core, the precise structural analysis calculated in BIM.

“We’re fortunate to have McAlpine Design Group and McAlpine Lifting Solutions inhouse to help design and plan the temporary works and major lifting operations,” says Amy.

Supply chain resilience has also been a major focus.

“The project includes 35 lifts and three escalators,” says Amy. “To minimise risk from global shipping issues, the escalators were imported from China more than six months before they were required on site. Similarly, the unitised facade panels were manufactured and stored in Italy six months in advance of installation.

“It has helped derisk the programme tremendously.”

With completion scheduled for 28 June 2027, the project is entering its final phase.

Most of the MEP plant has been delivered and will be installed within the basement and on the roof areas. Water source heat pumps for the showers and changing rooms are being fitted in the basement with air source heat pumps on the roofs of both towers. There remains some facade infill work before the hoist and tower cranes start being dismantled. The focus will then move to MEP testing and commissioning.

2FA has changed considerably since Amy came on board seven years ago and he says the key to delivering the evolving scope has been the collaborative culture on the project.

“We’ve been working with British Land for 10 years and there is a very strong team ethos – not just the McAlpine team, but the supply chain and the client team as well,” he says.

“No individual delivers a project. When jobs go well, construction can demonstrate some of the better sides of humanity. This project is a very good example of that.”