A design change now
means 18 Hanover
Square has a sixth-floor
atrium
NSC 17
June 19
consist of an adjacent six-story steel-framed
building at 1 Medici Courtyard that features
a retained façade along its main New Bond
Street elevation. This building will also
accommodate six lower ground and first
floor flagship retail units, with more than
3,100m2 of offices on the upper levels.
At the junction of New Bond Street
and Brook Street, a concrete-framed
structure will house further retail space
with six residential apartments above, while
abutting 18 Hanover Square, number 20 is
a listed Grade II Georgian house, which is
being restored to accommodate offices and
a restaurant.
“The success of this project has relied on
us continually liaising with the Crossrail
team, who are working directly below
our site,” explains Mace Project Manager
Stephen Wells.
“This has been crucial right through our
programme, from the demolition of the
site’s previous buildings to the erection of
the new structures.”
Discussing the use of steelwork, Mr
Wells adds that the material was chosen
for the project’s two biggest buildings (18
Hanover Square and 1 Medici Courtyard)
because of its speed of construction and
efficiency.
“Steel has also helped us logistically,
as this is a very tight site surrounded by
occupied buildings and with limited room
for storage. Steelwork is fabricated offsite
and delivered just-in-time, which means
less traffic on the already busy central
London roads.”
There is also another significant
advantage associated with using a steelframed
solution as WSP Director Steve
Miller explains: “A steel frame solution is
relatively lightweight compared to a solid
concrete solution.
“We had restrictions on loading of the
Crossrail structure, while the ability to
incorporate large clear spans and minimal
internal columns was also an advantage in
providing Grade A office space.”
1 Medici Courtyard was similar in
concept, with large clear spans and minimal
slab construction with downstand beams
for services to pass through. This frame is
founded on a raft which is located directly
over the Crossrail running tunnels and
escalator shaft. Keeping the new frame
light to match the previously demolished
building loads is said to have helped keep
the ground movements within acceptable
limits.
Steelwork contractor Severfield began its
erection programme with the 18 Hanover
Square building during October 2018. This
structure is based around a 12m x 10.5m
column grid pattern, but with the perimeter
structure columns set at approximately 3m
centres to align with the cladding design;
all of the columns are founded on the ticket
hall’s concrete roof.
The layout changes slightly for the three
uppermost levels, as the columns along the
main Hanover Square elevation are set back
to form a sixth-floor terrace and atrium
space.
The desire to minimise floor-to-floor
height in both steel-framed buildings led
to the use of shallow beams, which were
designed as plate girders in many cases, due
to the long spans involved.
“Modern fabrication techniques make
these more economic than they might
have been previously. Careful attention
to detailing was required to achieve the
complex ceiling services distribution
system which was usually in the same
plane as the beams; a mixture of circular
and rectangular holes was used to route
the services, with the latter requiring the
addition of stiffeners,” explains Mr Miller.
The use of steel also allows better
flexibility for tenants to provide openings
through the slab and other alterations
with reduced effect on the main framing
compared to a concrete solution. An
example of this is the sixth floor of 18
Hanover Square which incorporates an
atrium that extends up to roof level and
creates extra circulation space between the
three upper levels.
“The inclusion of the atrium at the
upper levels of 18 Hanover Square was a
design change requested by the client to
suit the tenant’s requirements,” explains Mr
Wells. “An advantage of using steelwork
was the fact that Severfield were able to
re-design this part of the frame during their
fabrication programme without any delays
to the overall scheme.”
The development will be completed
with a phased handover of the individual
elements, beginning with the residential
apartments on Brook Street late this year.
The entire scheme will be finished by late
2020.
Mixed-use
FACT FILE
18 Hanover Square,
London
Client: GHS Limited
Partnership (a joint
venture between Great
Portland Estates and
Hong Kong Monetary
Authority)
Architect: Lifschutz
Davidson Sandilands
Main contractor: Mace
Structural engineer:
WSP
Steelwork contractor:
Severfield
Steel tonnage: 2,450t
The project will create a
new public courtyard
/Braced_frames
/Facades_and_interfaces#Facade_retention_in_building_renovation
/Construction#Steel_erection
/Multi-storey_office_buildings#Speed_of_construction
/The_case_for_steel#Offsite_fabrication_for_precision_parts
/The_case_for_steel#Take_a_load_off_your_foundations
/Concept_design#Floor_grids
/Facades_and_interfaces
/Steel-supported_glazed_facades_and_roofs#Atrium_Roofs_and_Sky_lights
/Steel_construction_products#Plate_girders
/Fabrication
/Service_integration
/Multi-storey_office_buildings#Flexibility_and_adaptability
/The_case_for_steel