Níall McLaughlin
Architects

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.

ASSYRIAN CARPET

MARCH 2014

At the Assyrian collection at the British Museum, set amongst the colossal gateways of winged beasts with human heads and resplendent reliefs of bloody scenes from lion hunts, there is a large gypsum alabaster stone panel that was once a decoratively carved and painted door sill made up of inter-weaving patterns and borders, in imitation of a magnificent carpet.

Now wall-mounted in its current home, its intricacies can be clearly admired. Alabaster was discovered by the Assyrians circa 879BC to be ideal for carving fine ornament detail, and huge pieces were accordingly quarried, transported and installed as panels in the internal rooms of royal palaces where reliefs or pattern befitting a king would be carved with an astonishing level of skill within a surface depth of 10-15mm.

For Niall McLaughlin Architects T1 project, carried out for Argent on the King’s Cross redevelopment site, a motif from this ancient panel is being incorporated, along with other patterns from ancient Egypt to the twentieth century, into a number of repeating pre-cast elements that will form the building’s decorative facades and bring this enigmatic piece of deracinated design a new lease of life.

We are currently working towards achieving this in a collaboration with the client and the project’s contractor and a team of architectural pre-cast specialists. After carefully interpreting the motif and integrating it into the facade scheme; the proposed design is now being taken forward by mould makers who are utilising 3D routers to form prototypes of a pattern mould. The first results, which are being awaited with no little anticipation by the design team, will be analysed and the depth and colour of the reliefs carefully calibrated. Within a short period of time the small extract of pattern from an Assyrian carpet in existence nearly three thousand years ago will have a physical presence as part of a tapestry of other pre-cast components on this distinctive building forming, part of this ambitious development in the centre of London.

Image of Assyrian carpet pattern engraved in stone from Gottfried Semper Style in the Technical and Tectonic Arts; or, Practical Aesthetics, Getty Publications, 2004

Tim Burton studied architecture at London Metropolitan University and the ETH Zürich after a previous degree in Fine Art and Art History at Goldsmith’s College and experience within the film industry. He has also worked for Gramazio and Kohler’s Research Chair for Architecture and Digital Fabrication. Tim joined Niall McLaughlin Architects in 2012.  Since joining the practice, he has worked on a Peabody housing project in Whitechapel and the T1 Building for Argent in London’s Kings Cross. The T1 Building is a large mixed use development containing a district energy centre, an indoor sports pitch, car parking, shops, bars and 80 apartments.