Cinven – a 6 storey helical stair, London
The creation of a high end helical staircase through the centre of a central London building, built to look like it was part of the original structure but standing out for its subtle detailing and incredible form.
The Grade I Listed building at 21 St James’ Square was the work of The Ritz designers, Mewes & Davies, in the 1930s, who mirrored number 20 next door, a decision well justified as they were emulating the esteemed work of celebrated British architect, Robert Adam, from the 1770s. In 2018 it went through a substantial and thorough redevelopment to become an exclusive and opulent office building in the most expensive postcode in the UK.
Private equity firm, Cinven, made the upper 6 storeys their headquarters, where we designed, manufactured and installed the main staircase for the building, a helical feat of engineering from steel and stone. Property agents, Allsop, said of the fit out:
21 St. James’s Square has been designed to create a striking arrival experience, with a statement reception encompassing contemporary styling that emphasises the exceptional period design, and a concierge service that guarantees the highest level of comfort and convenience.
There is a rich history of St James’ Square, one of the most valuable postcodes in the UK with this particular address being Grade I Listed and widely regarded as one of London’s most prestigious commercial office addresses. Indeed, the previous inhabitant list reads as a ‘who’s who’ of British history, with even the Queen Mother of Elizabeth II residing there from 1906 to 1920.
The offices have been completed to a high specification, with luxurious interior finishes that complement the building’s historical significance. A revised floorplate and improvements to the layout and functionality of the building have sought to exceed the expectations of modern occupiers to create light, well configured space, whilst being sympathetic towards the building’s classical, regal architecture – Allsop
Architect
Spratley & Partners
Developer
Columbia Threadneedle Investments
Main Contractor
ISG plc
Handrails
Handrail Creations Ltd
Floor to floor height
3671mm / 3665mm / 3677mm / 3672mm / 3814mm
Treads
Folded plain plate closed riser steel treads welded between the stringers to provide support for tread finishes. Ditra Mat, Marine Ply and Silk Georgette treads and risers. Travertine to include 5 No. off brass inserts.
Balustrade
Art deco round bar wicket infill panels and plain vertical uprights constructed in panels for welding into the staircase structure with a flat bar core rail to receive the timber handrail. Inner balustrade to be formed with top plate of inner stringer as part of this element allowing a neat hidden welded connection for the balustrades.
Stringer
Staircase structure constructed in sections including inner and outer stringers with tread support plates welded between for site welding. Fabricated box section outer stringer with extended inner face including a feature lighting profile “groove” and provisions for acoustic soffit. Fabricated box section inner stringer with extended plate on outer face to extend down to soffit line to provide a clean face for site spraying. Stringer fabricated with the top plate removed.
Handrails
Ø45 French polished sapele with inner handrail connected to core rail of balustrade and outer handrails mounted directly to the wall using standard brackets both with a provision for an LED lighting strip.
Soffits
Provisions for an acoustic soffit “by others” included into the staircase structure with the wall side feature lighting groove included into the main staircase structure.
Other elements
20m2 silk georgette tiling to floor @ level 6 including ply & mat.
A feature helical stone staircase over six floors
A study in luxury, the bespoke interior has a stylish, timeless elegance celebrating its historical significance and highlighting opulence and exclusivity. The fit out could not have been any higher a specification and the result is perfection.
That is why Spiral UK were honoured to be contracted for the 6-storey helical staircase that winds its way up through the centre of the old building. A stair of that height is ambitious in itself, but this design was helical in nature, bringing with it a host of engineering and fabrication challenges. Helical stairs appear to be self-supporting, defying gravity as they arc through a space and causing tension points where they tether to a structure.
The design of this particular stair allowed for hidden support in the surrounding wall, the mild steel support structure cantilevering out from the wall leaving an atrium space down the centre of the stair, adding drama and wow factor. Gazing up from the ground floor, the dark balustrading contrasts with the white plaster work, accentuating the shape as it spirals upwards. The outer handrail is underlit by LED lighting cleverly concealed within the timber, mirroring the strip-lighting that curves around the edge of the soffits and reflecting off the brass inlaid nosing strips set into the vein cut Silk Georgette stone of the treads. It is no-expense-spared details such as these that make for such a polished finish, where these contemporary stairs look like they have always been a part of the fabric of the building yet manage to integrate modern features.
Overall, we are very proud of the outcome and pleased to have been a part of the on-going history of this iconic building.
Guide price
£700,000.00
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