Architect and Builder January/February 2016 | Page 39

ABOVE: STRUCTURAL WORK CARRIED OUT ON THE ORIGINAL FAÇADE

piles placed just inside the façade, in positions chosen to suit the
parking bays below. Holes were left in the slab for the main internal
structural columns which are not connected to the structure at
this point.
In places, RC lintols had been provided over wide door openings
formed during a previous renovation. Permanent steel columns were
placed on either side of these openings, on top of the new slab, to
support the RC lintol and brickwork above.
Somewhat fortuitously, there was a shallow basement below
the entrance foyer. Support for the existing basement foundations
was temporarily maintained by encasing an ‘island’ of sub-soil
material below them on three sides (with temporary gunite cladding
and anchors) as the surrounding parking garage basement was
excavated. New foundations and columns were cast on either side

TYPICAL OFFICE LEVEL

Touchstone House

of the ‘island’ to support an RC beam and slab grillage which was
constructed in the existing shallow basement space under the
entrance foyer. The entrance foyer walls are supported on yoke
beam elements of the grillage structure.
The ‘island’ of material under the entrance foyer was subsequently
excavated away and the load transferred onto the new structure.
Feasibility
The challenge was to maintain the heritage façade and foyer and
to create space for the parking bays required for the development,
at feasible cost.
It is testament to the boldness of the client, innovative engineering and cooperation between designers and constructors that
this goal was achieved at minimal cost.

15TH FLOOR PLAN

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