Mixed-use
FACT FILE
Ilona Rose House Development, London
Main client: Soho Estates
Architect:MATT Architecture
Main contractor: Sir Robert McAlpine
Structural engineer: Tier Consult
Steelwork contractor: William Hare
Steel tonnage: 2,900t
Model showing the
main elevation
“Using structural steelwork
was the obvious choice for this
project as a lightweight frame
was required.”
NSC 21
Jun 20
The cantilvering truss,
which forms the main
elevation, takes shape
and a similar long span arrangement to the
above ground levels was needed.
In the building’s south west corner, a
‘spotlight’ shaped atrium, dramatically cut
into the basement, will provide daylight
deep into the lower floors which are
designed specifically with the film and
creative industries in mind.
The circular void atrium is up to
5.8m-diameter and has been formed with a
series of 700mm × 700mm × 40mm curved
box sections set into the relevant floor slabs.
“The basement had a number of
temporary props, which could only be
removed once the floors had been installed.
We had to erect the columns, which are
typically two-storeys high, around the props
and then wait until the concrete slabs had
been installed before we could erect further
columns,” says William Hare Senior Project
Manager Richard Mosek.
Above ground, the retail areas and offices
are said to exploit the stepped massing
of the building to create over 1,100m2 of
planted external terraces for the benefit
of occupants. This means from level three
upwards, the building’s footprint gradually
decreases.
“The bulk and the massing of the
building is biased toward Charing Cross
Road, where the general height of the
surrounding buildings is greater. The
building then cascades down towards Greek
Street on its western perimeter,” explains
Tier Consult Engineer Jim Fraser.
“The need to reduce the mass on the
western side and introducing terraces led
to the use of a series of transfer structures
to support the changing perimeter column
lines.”
Radiating out from the central core,
the upper levels feature minimal internal
columns and open-plan areas are created
with numerous long span beams. The
project has 23 beams that span up to 19m or
more, with the longest being 19.6m.
According to William Hare Senior Site
Manager Ben Burns, the biggest challenge
for the steelwork programme is the main
Charing Cross Road east elevation. On this
side of the building there is a 34m-long ×
4.4m-deep cantilevered truss, weighing in
excess of 66t, positioned at first-floor level.
“It had to be broken down into sections,
no heavier than 16t each, so as not to
exceed the lifting capacity of the onsite
tower crane. To assemble the sections, we
had to use 35t of temporary support steel
and do three weeks of continuous 24-hour
onsite welding. This included a total of 64
full penetration butt welds with thicknesses
of up to 100mm, which is the equivalent of
one 5,400m-long weld.”
The cantilevering truss will create a
feature overhang above the ground floor
retail area. This architectural highlight
extends around the corner and along a
portion of the Manette Street façade. There
are no corner columns positioned at ground
floor as they would have been obtrusive to
the architectural design and so the truss was
introduced as the best option.
With no columns beneath, the truss is
effectively hung from the underside of four
plate girders positioned at the underside
of level two. The girders’ back spans are
Cellular beams have
been used throughout
the development to
accommodate building
services
Cut-out model
showing the rear of the
development and the
atrium
22
/Steel-supported_glazed_facades_and_roofs#Atrium_Roofs_and_Sky_lights
/Fabrication#Bending
/Construction#Temporary_works
/Long-span_beams
/Trusses
/Construction#Tower_cranes
/Construction#Site_welding
/Welding#Butt_welds