I’m standing next to a massive hole in the middle of London. This is going to be the basement and
foundations of a 34-storey new skyscraper that's going to rise above my head in the years to come.
It’s experiences like this that show you
just what goes into building in the middle of a major city and the extent of the
engineering that's required to make something as incredible as a skyscraper really happen.
Rising from this underground melting pot of concrete, steel and precision engineering,
the 170-metre 40 Leadenhall Street will make a dramatic
impact on the city’s skyline - and find itself as the first in a new series of skyscrapers
that’s trying to entice people back to the workplace in the wake of COVID-19.
With a striking design, prime location and green credentials,
this could just be the landmark new development London deserves, and the one it needs right now.
The square-mile City of London has seen more than its fair share of history; weathering wars,
crises and fires, all while standing as a global hub for business through the centuries.
But the period of 2020 and 2021 ranks among its most surreal chapters:
the changes of Brexit blending with a pandemic that’s forced people out of their workplaces,
impacting companies and the buildings they’re in.
There’s no question that the normally bustling City of London has been much quieter over the
past year, but it’s not just the easing of restrictions that’s going to change that.
Post-COVID, many of us are going to need a much stronger pull back to the office
and that’s where developments like this - and this concept of “destination offices” that offer
all kinds of things to their users - is going to really coming to the fore.
40 Leadenhall Street is one of the biggest buildings to ever get planning permission in
the City of London, rising from 14 to 34 storeys, with two basement levels.
The new complex in the heart of the insurance district will extend over
84,000 square metres of space, mostly dedicated to new offices, with retail units at street level.
While its size will automatically make it a prominent feature on the skyline,
it’s the building’s design that will ensure it really stands out.
Conceived by Make Architects, 40 Leadenhall’s styling was inspired by the Bauhaus movement,
as well as the skyscrapers that rose across Chicago and New York in the early 20th century.
Fearing the dark canyons that might be created by this new tall building phenomenon, American
cities introduced step-back rules that would ensure daylight could reach down to street-level.
The measure also enabled buildings to better manage wind-loads, meaning they could be built
taller. Countless skyscrapers emerged in this style throughout the 1920s and 30s,
but the most notable was undoubtedly the Empire State.
This neo-gothic style of architecture also influenced DC Comics’ vision for Batman in
the late-1930s and many people have likened the design of 40 Leadenhall Street to the franchise,
leading to it become dubbed ‘Gotham City’.
It consists of several stepped blocks that all fit with the surrounding massing, with the
highest point to the North and the rest gradually terracing downwards towards the River Thames.
The clever, staggered design allows it to blend in with the surrounding tall buildings
while preserving protected views or sight lines to St Paul’s Cathedral - a
rule that almost every other tall building here has had to consider.
Sitting on the western edge of the site - carefully protected and restored throughout the
works - the Grade II-listed 19-21 Billiter Street building will become part of the new development.
Sustainability and energy efficiency are also priorities.
Carbon emissions are set to be around 30% lower than current regulations
while the new building is due to meet several key energy standards.
Achieving all this on such a tight site in the middle
of one of the world’s biggest cities is not easy.
Rising to the challenge, main contractor Mace Group is working alongside WSP,
Make Architects and development manager Nuveen on the project.
Due to the building’s varying height, two cores are being constructed – one
at each end. These form the central part of each section and
give structural stability while housing the elevators and other services.
Both are side-core arrangements, which helps to create a large, open floor plate,
but the two cores are being built using different methods.
What made you make this enormous excavation to start with?
We’re currently bulk excavating the site, which is around 40,000 cubic metres of ground to take out.
The excavation is all relative to the build strategy that we’ve got. We’ve got
a top-down construction on the north core, which is the higher of the two towers
and then we’ve got a blue sky, bottom-up build strategy on the south core.
That top-down approach allows the team to work in two directions simultaneously,
with the floors above ground built at the same time as the basement levels.
Under the more conventional bottom-up method,
the lower levels are built first and work gradually proceeds upwards.
This huge excavation on the site really demonstrates the
challenges of building in a dense city centre.
With so many large buildings all exerting pressure on the ground,
an excavation of this size would take away some of the earth that their weight
is resting on - it would interrupt their so-called angle of incidence.
To avoid any risk of buildings collapsing, the team first dig and pour a series of overlapping
concrete columns in the ground, known as a continuous flight augering or CFA approach
and then cap them with a solid concrete beam - imaginatively called a capping beam.
Only then do they begin to excavate the site to construct the basement.
These enormous red steel struts help to push back the pressure of the surrounding
building’s foundations, before the solid concrete basement floors are installed.
To speed up the process and make construction easier on a restricted site,
prefabrication is being used extensively, forming a key benchmark for future Mace Group projects.
This is where building elements are manufactured under controlled
conditions in a separate facility before being transported in and assembled on site.
How is prefabrication playing a part in the project?
We’ve used offsite manufacturing as our key driver
around achieving spatial fit and the delivery and build sequence.
Has that really helped in terms of - on a
tighter sight like this - being able to lift things in pre-made?
Correct. We’ve fundamentally changed our approach to the early stages of design.
Working with Make and WSP we’ve managed to develop a design that’s fit for manufacturing
and we’ve really used that strategy, with the 3D model and the digital technology,
to deliver our prefabrication elements and the major components for the building.
Technology has played a critical role in keeping the project on
track and error-free - even during the pandemic.
Mace Group and Nuveen are using information modelling and Autodesk’s all-in-one BIM
360 software to plan and coordinate the construction of the building digitally.
This has helped to strengthen collaboration between the design and build teams.
Virtual 3D models of the entire project allow the team to stay a step ahead of
the physical build, improving efficiency and ensuring costly mistakes are avoided.
For people watching who don’t know about information modelling or have never used
it before - conventionally you would’ve coordinated the design to an extent, but the
real test was then you got here and you put the architectural and structural designs together.
But you’re doing that virtually now, so you're kind of building the building and coordinating
it in a virtual world before you do it for real out here, which cuts down on mistakes and errors.
Exactly. We’ve pretty much cleared the basement now, the cores are pretty much
done and obviously the steelworks so we’re well ahead of the construction going out on site.
When COVID hit we realised there would be difficulties with people
working on the model at the same time because everybody would be at home so
we looked at the BIM 360 Docs and Design system. It allowed all the
designers and trades to put their models on there in a live working environment.
This means that everyone - including those working from home - can track
changes to the models and ensure the right work is happening in the right areas.
Also from Autodesk, Navisworks and BIM 360 Glue were used to combine models together
and give the wider team easy access to them in the Cloud.
On the ground, BIM 360 lets the team on site verify progress by filling
out digital check sheets and attaching photos.
There’s even going to be a tag and track system, where all elements
arriving to site are given barcodes so they can be quickly located at any time.
I guess the million-dollar question is has it
made it easier? Have you had less errors on site? How has it been?
I would say - yeah we haven’t had any issues that
I’m aware of out on site at all so it’s all going well.
With its use of modern methods of construction and advanced tech, 40 Leadenhall Street is
now rapidly rising from its complex foundation and motoring towards its 2023 completion date.
Far from simply being the newest member of London’s skyscraper club,
in the wake of the pandemic the project represents the first
in a new age of tall buildings in the city - one where appeal is everything.
So that’s all from me down here at this awesome construction site.
This video was made possible by Autodesk - you can learn more about that at the link below.
And as always guys, if you want to get more incredibly cool stuff like this
make sure you’re subscribed to The B1M.