15 Clerkenwell Close is a mixed-use six storey building with a stone facade.
What may appear at first glance as a traditional concrete frame clad in stone has a little surprise in store for the keen eye. A closer inspection of the columns will reveal ammonoids, drilled wedge holes and saw grooves indicating that part of the story has not been told. In fact concrete columns and clip on stone have been rejected in favour of a simple system of solid stone load bearing columns.
The columns are designed to minimise the size and required workmanship as far as practical. An iterative approach to the design allowed each column to be designed and sized for the specific load carried by the column i.e. a higher load leads to a larger column.
In addition the finish of the stone is left largely as it was when it was cut from the quarry. Split naturally along the bedding planes of the stone, providing a contrast between the natural rough edges and lightly worked smooth edges.
The six above ground floor plates consist of thermally broken flat slabs perched on the stone columns, with the stability largely provided by the concrete core.
The sequence of construction was key to the success of the project. The limited access, proximity of adjoining properties and small working space meant that it was not safe for the concrete slabs to be installed whilst the stone workers were installing the columns. A construction sequence was developed to allow the concrete frame to be fully constructed on props prior to installing the load bearing stone facade.
Settlement and movement analysis was undertaken to ensure the expected movements did not unduly stress the building fabric, adjoining properties or the stone columns during construction, the striking of the temporary works, and in the permanent condition.