Chapter 3: Cover Story
Building Fifty Fenchurch Street

Where history meets innovation

Modern tall buildings are pushing the envelope in terms of design, structural efficiency, technical complexity and environmental impact. Constructing a tall office building in today’s Square Mile presents a series of technical and logistical demands which test to the limit those charged with its completion.

Take the City’s network of narrow streets and meandering lanes, most dating back to medieval times. These complicate the delivery of construction materials and the siting of cranes on space-constrained sites. Then throw into the mix working on a plot of land barely an acre in size, hemmed in by four busy thoroughfares, along with the need to protect and underpin a 700-year-old Grade I-Listed church tower, suspended in the air on 15m-tall stilts, and one can appreciate the work currently being undertaken to build the 36-storey tower at Fifty Fenchurch Street.

Building tall in the heart of one of the busiest cities in the world tests contractors and others to the limit, demanding the sort of military precision an army general might be familiar with. Here, Karl Wilkinson, Project Director at Multiplex, discusses further.

Developed by BNP Paribas AM Alts and YardNine, and designed by Eric Parry Architects in collaboration with Arup, once it’s completed towards the end of 2028, Fifty Fenchurch will be an all-electric office tower, featuring extensive vertical greening with landscaped terraces accessible from almost every office floor. The first phase of construction involves an open bulk excavation of three levels below ground for a basement box, which spans the entire footprint of the site. This space will include a new livery hall for the Clothworkers’ Company, which has occupied the site since gaining its charter in 1528.

The development also includes the conservation of two listed buildings: the All Hallows Staining Church Tower and Lambe’s Chapel Crypt. These will be reinstated into 1500sqm of new ground-level public realm, with part of the basement constructed beneath the church tower. This remains in place during construction, while the crypt has been carefully removed for later reinstallation.

The logistics of success

The efficiency and success of the construction programme is underpinned first and foremost by logistics. Working on such a relatively small plot of land throws up all manner of complexities. A pre-cast composite floor solution called MegaPlank is being used across the building, which helps with slimming down reinforcement and, subsequently, lowering the carbon content when compared with a traditional composite floor plate.

The nature of these planks, manufactured off site, results in the multitude of loose components, which feature prominently in more traditional ways of working being cast into larger parts. This sees them managed more efficiently and by a smaller but more specialised workforce. This is the product of our project mantra Safety and Quality by Design where we have identified known hazards and actively removed them through the design process so that our people are not exposed to the risks in the first place.

Consequently, and with parts ‘ready to fit’, the sequencing of deliveries on such a small site is critical. For example, floor slabs are loaded onto wagons in reverse order, so that when they arrive on site, they are unloaded in the correct order and installed from the core outwards.

Construction of concrete floor planks has to start very early in the programme, meaning design work needs to be completed much earlier to drive the detailed coordination and confidence between the steelwork producer, the facade contractor and the precast manufacturer.

And because many components are ready to go, tower crane dependencies are absolutely critical for the programme’s outputs. A tower crane is no good without a suitable pick point, which, together with the necessary loading bay strategy, makes for a very tight site.

As well as overcoming logistical challenges, the need for a carbon-efficient project, both in delivery and operation, is vital. A tall tower’s carbon impact ought to be a guiding principle from the initial design brief."

When reflecting on the tall towers that Multiplex has delivered over the past decade, Fifty Fenchurch Street will have roughly half the embodied carbon per sqm of a typical tall building, and will benefit from green energy produced by our solar farm, the first of its kind owned by a major contractor in the UK, enabling us to directly offset project emissions during construction."

Introducing RoboRigger

The nature of the Fifty Fenchurch Street site means the impact of wind on material delivery, particularly at height, can be considerable. Mitigating this and ensuring the safe delivery of the concrete planks being used, requires the use of a Roborigger, which uses drone-like technology combined with a series of fans to prevent a load spinning out on its ascent. Multiplex recognised early on that the Roborigger could be a game‑changer for safety, prompting investment and hands-on involvement in testing, refinement and user feedback. It has already deployed the device on 11 developments in Australia, and as developers build more towers, its use will surely increase.

Logistics also need to address the human element. In addition to lifting essential components, construction crews need to get to where they work. Early morning sees us prioritise getting superstructure crews to the top of the workplace as quickly as possible. Once that movement of people is cleared, up go the necessary materials. Windows will exist within a planning day for hoists to be booked out for taking people back down, and up again, during work periods.

While acutely timed delivery sequences are hugely important, so is minimising the number of on-site in situ works. A cohesive vertical transportation schedule underpins the effectiveness and productivity of an overall construction programme.

Guiding principles

As well as overcoming logistical challenges, the need for a carbon-efficient project, both in delivery and operation, is vital. A tall tower’s carbon impact ought to be a guiding principle from the initial design brief. Meeting tough carbon targets flows into every aspect of the structure, from the concrete mix designs to the amount of reinforcement being used, the type of glass in the facade and so on. When reflecting on the tall towers that Multiplex has delivered over the past decade, Fifty Fenchurch Street will have roughly half the embodied carbon per sqm of a typical tall building, and will benefit from green energy produced by our solar farm, the first of its kind owned by a major contractor in the UK, enabling us to directly offset project emissions during construction.

And as innovative as a new tower can be, for such an approach to be truly effective demands repeatability. Yet this runs counter to the bespoke nature of any construction project. Add in frighteningly tight margins, and for some the cost impact of an innovative approach can be hard to justify. Standardising what’s invisible and being able to make bespoke what one can see, will become the norm.

More at: www.multiplex.global/uk