A STONE GLOSSARY
MAY 2018
William ‘Strata’ Smith’s 1815 Geological Map, the first nationwide geological map ever published.
We are in the process of choosing the stone to be used for a new building in Cambridge. It has been an apparently exhaustive journey through marbles and limestones from the UK, Europe and beyond. We amass endless samples, and talk in detail to quarrymen, masons and engineers about bed heights, weathering, and reliability of supply, as well as the inevitable costs to quarry the stone, cut it to shape, and fix it together to form a building. One of the most fascinating elements of this process are the specialist terms used to describe building stones and their properties. Below is a list of a few favourite words, ordered to explain the material properties that have so far governed our explorations for this new project.
The Clipsham Quarry at Rutland in Lincolnshire. Clipsham Stone occurs in the Inferior Oolite of the Jurassic System, where it was laid down between 174 and 163 million years ago. Clipsham is a popular building limestone with a characteristic golden colour. We have recently worked with it at Bishop Edward King Chapel in Cuddesdon and the Sultan Nazrin Shah Centre in Oxford.
Bedding plane
Many building stones, including all limestones, are sedimentary rocks, formed by the gradual settlement and compression of underwater sediment over millions of years. The directional way in which they were formed governs their properties and how they can be used as building stones. Most UK limestones must be used ‘naturally bedded’, i.e. orientated in the building in the same way that they were formed in the ground. This means the height of the blocks is limited to the depth of the bed, rarely more than 1m in the UK. ‘Face-bedding’, when blocks are laid so their bedding planes are parallel with the vertical face of the block, can lead to rapid weathering and crumbling.
Metamorphic
A stone that began as another type of rock and changed as a result of exposure to heat and pressure over geological time. Marble was originally limestone, and is chemically identical to it. However, the metamorphic processes changed its physical properties so that it does not have bedding planes, and can be cut and orientated in any direction. This makes it ideal if tall blocks are required.
Precipitation
The chemical process by which Travertine is formed, usually when geothermally heated water is exposed to the air, causing it to degas and carbonate minerals to precipitate out from the water. Although a type of limestone, its distinctive formation means it also doesn’t have bedding planes and is workable in much longer, thinner pieces than sedimentary stones.
Oolitic
A type of limestone made from an amalgamation of individual grains called ooliths. An oolith is a tiny carbonate particle surrounded by concentric layers of calcium carbonate, which were deposited as the ooliths were rolled around on the bed of the clear shallow sea in which the stone was formed. This gives the stone an even structure so it can be cut or sculpted in any direction, a characteristic which makes oolitic stones ‘freestones’. Portland Stone is an oolitic limestone used extensively in London’s historic buildings, perhaps most famously in churches by Cristopher Wren and Nicholas Hawksmoor, including St Paul’s Cathedral and Christ Church Spitalfields.
FIAT-MIRAFIORI
NOVEMBER 2014
FIAT-MIRAFIORI, Turin, Italy
Located in a suburb of post-industrial Turin, once the ‘Fordist world’s most prototypical town’, the proposal is for a campus university sited within the endless 20m x 20m concrete grid of Fiat’s behemoth Mirafiori plant (1939). The proposed high-speed railway link between Lyon, Turin and Budapest is seen as a driving agent in re-establishing the city and its traditional expertise in manufacturing within a wider European context. The project is an exploration of the open-plan, balancing the generic with the particular by interweaving new programmes and functions into the repetitive matrix of the existing concrete frame.
The design focuses on the sectional distribution of the master plan, with workshops, offices, lecture theatres and public squares at ground level, and housing, communal facilities, nursery schools and shared gardens inhabiting the building’s roof. Occupying a site equivalent in area to Turin’s historic centre, the project envisages Mirafiori as a new city quarter articulated by the shifting presence of production, research, commerce and living.
The images above depict an installation built as a 1:500 representation of the site. Conceived as a simple armature, the model afforded a large-scale, neutral, three-dimensional surface that momentarily held the light and colour cast by a moving, digital projection. I was interested in how this plain surface could take the role of both narrative device, upon which the dynamic history of the building’s conception, construction and early operation could be retraced and re-recorded, and serve as a framework within which to test differing scenarios for the site’s re-inhabitation.
Reflecting on the experience of making this installation, I have now come to realise that what had started out as process of historic site analysis, drawn to scale and illustrated through light, had become (quite unintentionally) suggestive of a proposed architecture. Experienced at 1:1, the installation produced a dreamy environment of diaphanous surfaces, coloured light and whirring sound. Whilst the subject and intent of the installation was still historical, it no longer just retold but ‘produced’ a shifting architecture, temporary in nature and formed through the lightest touch of light, colour, diffraction and shadow. Exploring this disjunction between intent and outcome a bit further, I can now recognise that through the initial planning, fabrication and composition, activities that at the time I only understood as a means to an end, I had already made a series of decisions about the installation’s form, scale and materiality. The subsequent processes of animation, projection, filming and finally editing footage and sound together, added further faculties of decision, critique, editorship and importantly chance or accident. Each, in turn, contributed an iteration – an opportunity to reflect, develop and transform – which, slowly but surely, transformed a representation of the past into a proposal for the future.
Alastair Browning is a member of the Auckland Castle team at Niall McLaughlin Architects. His thesis project FIAT-Mirafiori, undertaken whilst studying with Unit 17 at the Bartlett and tutored by Niall McLaughlin, Yeoryia Manolopoulou and Michiko Sumi, has been selected as one of 11 highly-achieving postgraduate projects from across London’s architecture schools to exhibit at the Architecture Foundation’s Futures in the Making Exhibition.
Futures in the Making is being held at Feilden Clegg Bradley Studios, Twenty Tottenham Street, London W1T 4RF ( Until the 28th November 1.45 – 6pm)