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.
A STYLE FOR OUR TIMES?
NOVEMBER 2015
“The way to make good architecture – that is, to respond with dignity to the relentless jostling of theoretical positions and of the buildings themselves – can be to say very little indeed and just to enquire into what a particular place might, by way of buildings, most need”
Niall Hobhouse in Translations: Florian Beigel and Philip Christou, Christoph Merian Verlag 2014
Each year the Stirling Prize shortlist sparks debate about contemporary architectural style and it was no different this year, particularly with such a distinctive set of buildings. The prize is “presented to the architects of the building that has made the greatest contribution to the evolution of architecture in the past year” and so any building shortlisted could be considered to exemplify a style for our times.
In practicing architecture I have been conscious of past and present styles or trends and how these influence design. The offices I have worked in each have different design styles and a different set of architectural references. This variety has enriched my experience of design; as a result, I do not consider myself to have a fixed stylistic agenda or claim a particular preference for one style over another.
I have now been at NMLA for almost a year, working on one project but well aware of the rich variety in the practice’s past and present portfolio. Whilst there may be a discernible common language in the architecture, I would say this transcends any one particular style. To pick three of the most celebrated projects, the Chapel at Ripon College is very different to the Fishing Hut which is very different to Darbishire Place. Of course these buildings have different briefs but perhaps their ‘style’ is most significantly determined by the ‘place’ they inhabit (where ‘place’ refers to location and context – physical, social, historical and political).
The Chapel sits on a sensitive site. It must respond to its bucolic setting in a clearing amongst trees, the historically-significant college building stock behind and the views to and from the valley below. The Clipsham stone is in keeping with the Limestone of the other college buildings. The smooth base helps ground the building in its natural setting whilst the rough-cut dog-toothed stone alludes to the craft evident in the historic buildings nearby and has an organic quality whose textured surface perfectly captures the shadows of the trees. The clerestorey windows glow as a halo and act as a beacon on the hill when seen from the valley below. Rowan Moore described the chapel as sitting “comfortably amid Cotswold scenery and gothic revival architecture”.
The Fishing Hut is set in the landscape, between water and sky. Its simple form and construction are familiar to rural or agricultural settings but the level of craft and its quality materials make it delightful for the user, elevating it beyond purely functional. With its operable screens and shutters, it is both solid and transparent, as much about shelter, security and shade as it is about light, air and opening up to the landscape it inhabits.
At Darbishire Place the new brick block reflects the massing and characteristics of the existing Peabody estate blocks. The brick selection and white precast concrete window surrounds complement the brick and white-painted window reveals of the Edwardian buildings around the courtyard. Inset balconies enable the new façades to have a flatness akin to those of the surrounding buildings. A simple kink in building’s footprint allows the block to work with its context on both sides – a longer elevation addresses the street while a more compact elevation works with the proportions of the other courtyard façades. This kink also provides a route in from the street and so the new block can complete the courtyard without closing it off.
In terms of these three buildings, it is perhaps more difficult to identify a common architectural language than to comment on how they respond to place. I think they are all concerned with light and shadow and each display a level of craft in their execution. For me though the architecture of each project has a fineness. The fragile crown of stone fins and frameless clerestorey windows at the top of the chapel; the intricate timberwork, lightweight permeable envelope and the slight cantilevered deck hovering over the water to the front of the fishing hut; and the open corners and slender corner posts containing the inset balconies to Darbishire Place. It is these moments of finesse that unite the three buildings and other projects in the office.
Style has played an important and often polemical role in the development of architecture over the last 150 years. However, whilst we can entertain debate about a cycle of trends in design, what style is ‘now’ and what is coming next, it seems more pertinent to be aware of the wide variety of styles and take influence from sources that are most appropriate to any one project’s place.
In the same vein as the opening quotation, we should not be concerned with a particular style for a particular time, but rather a particular style for a particular place.