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October 18
Situated on a prominent site, Four
Pancras Square demanded a strong
identity that resonated with the
site’s industrial heritage. This was
encapsulated in Eric Parry Architects’
competition-winning design, which features
an expressive, exposed weathering steel
exoskeleton frame.
The building was designed as a
speculative office, aspiring to exceed the
British Council for Office specification and
it was the first office to achieve a BREEAM
2014 rating of ‘Outstanding’.
Similar to the adjacent buildings, Four
Pancras Square is an 11-storey commercial
block offering Grade A office space with
ground floor retail zones.
The steel exoskeleton forms the exterior
of the entire building, supporting all of
the internal floor slabs along each of the
four elevations. The external steelwork and
the floors are connected at key strategic
locations that allow differential movements
between the two to occur.
The main feature of this steelwork is a
storey-high Vierendeel truss that encircles
the building at first floor level.
“The main function of the steel truss is
to create a 27m-long column-free façade
along the building’s main entrance elevation,
that not only overlooks the public realm
but forms an important architectural
‘open letterbox’ between the building and
the outdoor area,” explains BAM Design
Associate Mike Hayes.
Aside from the main entrance façade,
the truss allows the other elevations to have
ground floor column spacings of up to
15.6m, which gives the building the desired
architectural long span look. Above the
truss the steel columns are aligned with the
internal concrete columns at the shorter
4.5m spacings.
Weathering steel has been used for
the entire skeleton because its hue will
subtly change over time lending itself to
the desired heritage appearance. Another
benefit of using this type of steel is the fact
that, even though it will remain exposed, it
will not need painting or any maintenance
throughout its lifetime.
“As weathering steel is only produced
in plate, all of the columns are bespoke
fabricated sections, with hidden internal
connections for a clean aesthetic
appearance,” explains Severfield Project
Manager Gary Dooley.
Erecting the steelwork began with
the installation of the storey-high truss,
beginning with the 27m-long column-free
span along the entrance elevation.
The truss was fabricated by Severfield
and then brought to site in 18 sections,
including four corner pieces. The truss
elements measured up to 17m long with the
heaviest weighing 72t.
The judges recognised the strong
technical collaboration of the entire team to
deliver the architect’s vision of an expressed
weathering steel exoskeleton without
compromise. This was achieved through
creative development of key technical details
to address thermal bridging, differential
thermal movements, fire performance and
weathering. The building’s elevations are a
celebration of steel.
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SSDA 2018 C O M M E N D A T I O N
FACT FILE
Architect: Eric Parry Architects
Structural engineers: AKT II and BAM Design
Steelwork contractor: Severfield
Main contractor: BAM Construction
Client: King’s Cross Central Limited Partnership
Four Pancras Square,
London
Featuring a weathering steel exoskeleton, Four
Pancras Square is the last of six new commercial
buildings within King’s Cross Development Zone B.
© Dirk Lindner/Eric Parry Architects
/Visually_expressed_structural_forms#Expression_of_bracing
/BREEAM
/Multi-storey_office_buildings
/Trusses#Vierendeel_trusses
/Facades_and_interfaces
/Weathering_steel
/Paint_coatings
/Weathering_steel#Plates
/Steel_construction_products#Plate_girders
/Construction#Steel_erection
/Fabrication
/Fabrication#Handling_and_transportation
/Thermal_performance#Thermal_bridging
/Fire_and_steel_construction#External_steelwork_in_fire