Ketton ashlar facade, Redmiles Lane
Ketton stone is a Jurassic oolitic limestone, cream to pale yellow or pink in colour which has been used as a building stone since the late medieval period.
The village lies within a narrow band of oolitic limestone which stretches from the Humber, down through the Cotswolds and into Somerset and Dorset, ending up at Portland on the south coast. This seam produces some of the best building stone in the country, which can be seen in towns such as Stamford and Bath.
Oolitic limestone is a carbonate rock made up mostly of ooliths (or ooids), which are sand-sized carbonate particles composed of concentric layers. These layers were formed around the grains of sand or shell fragments on a shallow sea floor, rather like the modern Bahamas, near the end of the Jurassic period (over 135 million years ago).
The stone has an even structure, rather like cod roe, and it can therefore be cut or sculpted in any direction. This feature, coupled with hardness, colour and durability, gives the stone its quality as a building stone. This flexibility allows the stone to be used in the following ways:
Ashlar facings: where the stone is dressed to form perfectly squared blocks. Ashlar is used for high-quality facades and for dressings such as window architraves and quoins. Ashlar facades tend to face a rubble stone wall behind and are often about 100mm in depth.
Coursed rubble stone: where stone is more roughly dressed into blocks of similar size which can be laid in courses. This is the most common building material for vernacular buildings and may be combined with ashlared dressings around windows and doors.
Carved/sculpted detail: where the stone is carved as ornamentation on buildings of high status, such as churches, stately homes, colleges and public buildings.
Ketton stone is sometimes combined with other local building stones. The early fabric of St Mary's Church is constructed from Barnack stone, which is a shelly grey limestone which was quarried from shallow pits in the medieval period. Other buildings use ironstone, which is a dark brown limestone found in western areas of Rutland.
Traditional roofs use Collyweston slates, which are split limestone slates mined at Collyweston and Easton-on-the-Hill just over the border in Northamptonshire. There is only one thatched building remaining in the village, which is the barn of Garden Cottage in Church Road. Pantiles are rare, but feature on some agricultural buildings.
The main deposits of quality stone are to the north and north east of the village and these have been extensively worked. The early hand-worked pits, as shown on the 1768 map of Ketton, have now been swallowed up by the huge quarry serving the current cement works. However, there are still good examples of early stone pits, rock piles and other features visible in the old quarry workings off Pit Lane, which are accessible to the public (see Local Walks for more information on access).
Ketton Stone has been widely used for prestigous building projects, most notably at Cambridge where it has been used in many of the colleges for over 300 years. Examples of notable buildings erected in Ketton stone include: