The Stone Exoskeleton
As cost consultants, we’re always following construction trends. The stone skeleton of Amin Taha's RIBA award winning 15 Clerkenwell Close definitely caught our eye.
The London housing block built by Amin Taha + Groupwork features a a rugged exoskeleton of raw quarried limestone. Taha chose to use stone to reference an 11th-century abbey ruin that forms part of the neighbourhood's rich history. It certainly stands out amongst the brick-clad mid to late century buildings that surround it.
According to Taha’s interviews in Dezeen, he wanted to construct a stone exoskeleton, that ensured the use of the stone was more than just decorative. The framework on 15 Clerkenwell Close is separate from but structurally connected to the building envelope, which allows for the creation of a continuous curtain wall set back from the façade. Although many design lovers and developers will hail this project as a creative gem, it incidentally ruffled quite a few feathers in the local planning office, and even managed to escape a demolition order!
As is the case with any exoskeleton, one of the main advantages is that it can free up interior space that would otherwise be required for columns and other structural supports. This creates an extremely flexible floorplan that can be easily adapted. The residential units in 15 Clerkenwell Close feature column-free, open-plan living spaces and bedrooms all positioned around the central core.
Aside from the design, the part which really excites us as cost consultants, is that the choice of stone exoskeleton could be more cost effective! Following the success of 15 Clerkenwell Close, Groupwork collaborated with structural engineers Webb Yates to design a 30-storey stone office block. The conceptual exercise investigates how the cost and sustainability impact of a skyscraper with a stone structure compares to one with a concrete or steel structure. The research favours the stone option. It was found that large commercial buildings could be built more cheaply and with less of an environmental impact using stone, rather than concrete or steel. According to Amin Taha, "It's cheaper and enables a 90 per cent reduction of embodied CO2" when compared to typical steel or concrete frames.
This is definitely an exciting trend to look out for and an area that we will be keeping a close eye on here at Greenway Associates! The exoskeleton, and indeed, the potential of using a stone exoskeleton, could be quite attractive to the type of developer with a focus on the whole building life cycle, or with a focus on the greater saleability of a building that can more readily change use.
We could see the exoskeleton being of particular interest to long term owner operators, who are looking for sustainable developments that facilitate an easier change of use. The column free floor plates allow for more cost efficient conversion, for example, from office to residential.
In our 20+ years of experience in providing cost consultancy for hotels, the placement of columns significantly affects net usable floor area, and thus, the bottom line for hoteliers. Should this technique be adopted by hoteliers, it could resolve this most important aspect of hotel design, in addition to offering aesthetic and sound proofing benefits.