London’s Mayfair exclusive Claridge’s Hotel is
more than 200 years old and has a long history of serving royalty, politicians, and celebrities.
However, after decades of underinvestment decline was beginning to show and the hotel needed
to undertake a massive renovation project to prepare for the future and compete with the other
luxurious London hotels. The problem was that the hotel is a grade two listed protected building
so structural changes were severely limited. Also, the hotel's centre London location made
it impossible to extend at street level. Another problem was the hotel owners didn’t want to
close or disturb guests during renovations so any building work would need to be done
silently and out of sight of the 5-star guests. Well, what did the hotel decide to do?
Let’s find out!!
Claridge’s Hotel wanted to add 50% to its
size by adding a 5-storey 6000 m2 (65,000 ft2) mega-basement and if that wasn’t enough,
they planned to add 4 more storeys on top to create 72 new rooms and suites including £100,000
($120,000) per night penthouse super-suite.
Back in 2007 the initial vision
for expansion was quite modest, the hotel owners explored the possibility of
adding a two-story extension to their prized property. However, with the financial crash
in 2008, those plans were put to the side.
But in 2015, the Maybourne Hotel Group dreamt
even bigger big and began discussions with their contractor. They explored the possibility of
adding a stunning five-story basement below their cherished property. The only reason the contractor
was awarded the deal was by promising to keep the hotel operational and guests uninterrupted
throughout the construction process.
The aim of the project was to delve a
basement as deep as the hotel soars high. Spanning over 6000 m2 (65,000 square feet) across
5 impressive levels, the subterranean marvel boasts a wealth of decadent amenities. It would
include the hotel's very first swimming pools, a 650 m2 (7000 square feet) spa, and an
underground wine cellar housing the finest vintage wine. Also located in the basement
would be a bakery and in-house chocolatier. And for the hotel staff, this underground haven
offers a complete experience with a full-service catering kitchen, restaurant, lounge area,
changing facilities, showers, and laundry, all designed for luxury and comfort.
The excavation and construction of the basement was carried out by a large
project team. Construction crews worked 24 hours a day in 12 hour shifts,
including miners from Donegal, Ireland. These miners were selected due to their expertise
and their knowledge in some of the world’s biggest underground engineering projects – including
the Channel Tunnel and the New York subway. Two miners worked together in one hole
and to avoid disturbing the guests above, with all the work needing to be done by hand.
The first phase involved digging a network of tunnels beneath an 80-year old concrete reinforced
slab, just two metres underneath the guest floors and across the width of the Art Deco wing of the
hotel. Then the miners began to dig vertically to create the foundations of the basement. The
miners had to hand dig down 32 meters for each of the 64 piles used, 64 times. Then they had to
remove 45,000 tons of dirt from beneath the hotel. Initially all materials going in and out of the
site had to pass through one single 2 and a half metres wide hole, at the back of the property.
Once each pile was completed, concrete foundations were poured and then 23 m deep columns
supported the hotel's original concrete slab. This new support structure needed a certain amount
of flexibility so the hotel above would not crack, bend or endanger the overall building strength.
Hydraulic jacks capable of supporting the weight of three jumbo jets, 1,100 tonnes, were added
to the top of each of the columns to maintain the hotel's level. They can adjust up to 2.8
centimeters to prevent any sinking or rising. Due to the high-stakes of the project,
the old concrete slab will be monitored continuously for three years through sensors
which will take readings every five minutes.
After two years of hand-digging and the hotel
successfully supported on the new columns, this then allowed construction workers to perform
a top-down excavation of the earth around the columns to create the new 5-storey basement.
Removing 5000 cubic metres of earth from each of the 5 levels was made easier using heavy
machinery that was assembled in the basement. After the earth has been removed, thousands of
tonnes of reinforced concrete were poured to form the floor and the ceiling of the floor below.
After only a year the excavation team were able to successfully dig to 5th underground floor.
Once the fifth and final reinforced-concrete floor was installed, the miners faced an additional task
of digging two remaining tunnels. In an effort to upgrade the hotel, the engine room that housed
the plumbing and electrical wiring was relocated from the rooftop of the Victorian wing to the
lowest level of the basement, 55 meters below.
This new central hub required connection to
the existing network of pipes located on the other side of the hotel. To accomplish this,
while they began excavation of the basement, the team simultaneously dug two 4-meter wide
vertical tunnels under the Victorian wing. The most challenging aspect of this operation
was the connecting of the vertical and horizontal shafts but thankfully the tunnel and shaft lined
up perfectly and the connection was flawlessly.
This then signalled that
basement shell was complete!
During the excavation of a basement,
encountering water is a common occurrence. This project was no exception, as water
attempted to seep through any weak points.
Many cities, including London, underwent major
changes during the Industrial Revolution. One of the consequences of the rapid urbanization
and industrialization of these cities was the diversion of many rivers underground to make
room for new buildings and infrastructure. As a result, Claridge's, like lots of buildings in
central London, sits atop an underground river.
The project engineers rerouted
this underground river with the help of vacuums and pumps before excavation
began. However, despite these measures, some groundwater continued to penetrate the basement.
The construction crews were forced to make repairs several times due to water infiltrating the
construction joints in the walls. This instability presented a challenge for the next phase of
the excavation - constructing several tunnels, each five meters in length, which would
connect to a new stairwell and lift shaft and serve as the staff entrances to the new spa.
Another problem that was discovered during the construction of the basement was the loud sounds
coming from the London Underground – The Tube. Despite the developers' belief that the hotel’s
basement was far enough from the underground train lines, the newly built basement amplified even
faint noises that traveled through the ground. As a result, the tube sounds were heard through
the walls and basement pillars. To solve the problem, a team of acoustic engineers were
hired and they came up with a simple solution: building small spa treatment room boxes within
an outer box surrounded by acoustic insulation. The smaller spa treatment rooms were then attached
to the walls using acoustic rubber springs.
The floor of these inner rooms was elevated above
the concrete floor through the use of springs. For the walls and inner roof, an acoustic
quilt was sandwiched between pieces of acoustic plasterboard. The purpose of this was to absorb
the vibrations and keep the sound from traveling, which successfully solved the problem!
In conclusion, the basement renovation of London's Claridge's Hotel was a remarkable undertaking
but seven years after the construction began, the renovation was completed in September 2021.
Faced with challenges like strict regulations and the need to maintain guest comfort,
the hotel embarked on an ambitious plan. The addition of a 5-storey mega-basement
with luxurious amenities transformed the hotel's offerings, creating an
underground haven of opulence. Skilled miners and innovative solutions overcame
obstacles, ensuring the successful completion of the basement shell. But this is only the
first part of the captivating transformation. Join us for the second part of the video, where
Claridge's Hotel's allure reaches new heights. Witness the creation of 72 rooms, including
the extraordinary penthouse super-suite. Stay tuned as this iconic establishment
redefines luxury. Thank you for joining us on this exploration. We look forward to
welcoming you back in the next video.
