We worked very closely with the interior design architect and contractor to deliver these two stunning feature staircases in very challenging conditions.

The roof was enclosed by the time we were awarded the contract and it was no longer possible to lift these units into place by conventional means. Indeed, access for the staircases was limited to the passenger lift and hence units had to be manufactured to fit within these restrictions.

The straight staircase was manufactured with a curved and variable soffit with an incredibly slender waist and went from Level 1 to 2. A rebate was cast into one side to accept the glass balustrade. The staircase was made in 5 units with cast-in post-tensioning ducts. The elements were brought to the work area on trollies, lifted into place and propped in position. The bottom 3 elements were tensioned together and likewise with the top three elements. Precision in the formwork and installation were paramount as the staircases were to be finished with a very thin layer of polished plaster.

The top treads were rebated to accept an ultra thin 15mm specially reinforced fibre concrete tread width and riser section which contrasted with the polished plaster finish elsewhere.

With an overall length in excess of 8 metres and an active waist of less than 150mm, it is quite a feat of engineering and aesthetics despite the site constraints.

The feature helical staircase cantilevering from the curved central concrete spine beam and handrail was designed to resemble a drill bit and hence represent the client’s core business. This was located at Levels 5 to 7 and leads into the executive workspace.

Once again, the same constraints existed. The staircase compiled of central spine units, cantilevering waist units, landings at two levels combined with balustrading. After these elements were installed, curved triangular shaped treads were placed on the waist elements. Once again, the staircase was designed to be incredibly slender. Additionally, dowel and grout connections had to be very precise.

There were significant temporary works both in respect of propping the staircase in the temporary condition as well as providing a safe and constant access as the structure developed.

The soffit and strings of the staircase received a thin polished plaster finish. The final results are quite breath taking and have achieved the feature staircase that the architect desired.

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