Chilterns Hills:

Geology, Landscape, Materials and Vernacular

 

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Fig. 1. Image of the Chiltern Hills

 

The Chilterns is renowned for rolling chalk hills, steep valleys, winding roads and picturesque villages with brick and flint cottages. To many- visitors and residents alike- it is one of the finest British landscapes. Since 1965, the majority of the Chilterns has been protected by the status of ‘Area of Outstanding Natural Beauty’ (AONB), helping to conserve and protect this special landscape and its architecture.

 

However, 

    - How did this landscape come to be? 

and 

    - What has influenced the design of its picturesque villages?

 

This short article aims to reflect on the Chiltern Hills as a whole, reviewing its geology, unique landscape and vernacular architecture, in order to understand the local materials and how they are used within the Chilterns to develop the vernacular style we see today. 

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Fig. 2. Map of the Chiltern Hills area

Geology of the Chiltern Hills

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Fig. 3. Image of Chiltern Hills

 

The Chiltern Hills are a chalk ridge which cuts across Oxfordshire, Buckinghamshire, Hertfordshire, and Bedfordshire. The Chiltern Hills were formed over 65 million years ago, when chalk rocks started to be compressed and uplifted under huge tectonic forces. Flint was formed during the layering of the chalk at the base of the sea bed, some organisms are made of silica, and when these organisms die the silica is incorporated in the sediment. The silica gradually transforms into quartz (flint).

 

Then, during the glacial and interglacial periods material mostly clay with patches of sand and gravel, was deposited in layers over the chalk, by glaciers, melt waters and wind. During this period and after the ice ages, peri-glacial conditions froze the chalk and meant that it was impermeable to water, allowing surface water to erode the rock and create valleys.

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Fig. 4. Sectional drawing of the geology of the Chiltern Hills

The effect of people on the Landscape

 

People have been affecting the landscape of the Chiltern Hills since the first settlers arrived here, when they began to cut down trees and make way for ‘farming’. However it can be understood that the majority of the settlements (hamlets and villages) in the Chiltern Hills have origins between the 10th-13th century. These settlements vary in pattern, however one of the most quintessential settlement patterns can be seen where villages have built up around a focus, such as; a common, green or church. In the 18th and 19th century the landscape was further divided, with the introduction of the Parliamentary Enclosure Act, which saw a change in field pattens and the use of common land. The 20th century continued to see a change in the field patterns (some fields being sub-divided and others made larger), however a key development during the 20th century was the introduction of modern woodland and land for recreational uses (such as golf courses and playing fields). 

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Fig. 5. View across the Chiltern Hills

Case Study 1: Town End, Radnage

 

Town End, Radnage, is not recognised or highlighted as a Conservation Area, however within a square kilometre is contains; 8 Listed Buildings (including a Norman Church), evidence of historic settlement, coaxial fields (potentially dating back to bronze-age or medieval times), ‘irregular’ pre 18th century enclosures, 19th century enclosures (potentially related to the Parliamentary Enclosures Act), Prairie fields (the enlarging of historic fields to allow modern methods of farming), 20/21st century enclosures and a new build 21st century house. Analysis of this small area highlights how the Chiltern Hills has developed from the Bronze Age and how they are still developing today.

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Fig. 6. Town End, Radnage map highlighting history of the landscape

Materials 

 

The Chiltern Hills geology means that it lacks stone as a readily available building material. However building work was still undertaken with the materials which were available; bricks and tiles were produced by local brickmakers from clay dug out of the fields, flints are abundant, found in the chalk of the hills and timber was easily available from the wooded landscape. In addition clunch, a form of hard chalk has also been used for building in the Chilterns, this is found in small pockets throughout the Chilterns. Sarsen stones (sandstone blocks, similar to those used at Stonehenge) can also be found in isolated pockets near Hughendon and Prestwood, these can also be found in some of the vernacular architecture of the Chilterns. 

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Fig. 7. Image of a 17th century building which incorporates a variety of chiltern building materials

 

 

Chalk

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Fig. 8. Image of Chalk lump

 

The Chiltern Hills are primarily made up of chalk, a type of limestone which formed from marine sediment build-up under the sea over millions of years to form a sedimentary rock which is chemically calcium carbonate. Chalk has been extracted from the Chilterns since Roman times. 

 

Chalk/ limestone is calcium carbonate which is the key ingredient in lime mortar. The chalk is burnt to produce quick lime (calcium oxide), this is highly reactive with water. There are 3 ways of then converting the quicklime into a lime mortars; slacking, hydrating or hot mixing. However the principals all remain similar, water is added directly to the quicklime which results in calcium hydroxide forming. Depending on the method, aggregates may already be present in the mix or the calcium hydroxide will need to have suitable aggregates added to produce the lime mortar. 

 

Cement (Ordinary Portland Cement) is also produced from calcium carbonate (chalk) however this is formed by heating the chalk together with clay, to form clinker. This clinker is then ground and gypsum (calcium sulfate dihydrate) is added to the mix.

 

Although similar in how they are produced, lime and cement have differing characteristics and it is important these are understood before either is used. For example; lime is breathable and much softer so more suited as a mortar for handmade chiltern bricks. 

 

Historically lime was often burnt in the same kilns as the bricks were fired, this kiln then provided two of the key materials used in local vernacular buildings. Lime is the key ingredient in both lime and cementitious mortar, so the quarrying of lime has been continuous and is still relevant today.

Case Study 2: Chinnor Chalk Quarry

 

The largest chalk quarry in the Chilterns was located in Chinnor, Oxfordshire. This quarry began extracting chalk for lime in 1908, however in 1919 the diversification into the production of cement began. The ‘Chinnor cement and Lime co.’ was founded in 1936 and the company expanded greatly until in 1963 it became one of the six largest cement factories in the UK.  At the height of production, the quarry manufactured 5,600 tonnes per week of cement. The quarry was due to close however its life extended by a sudden need for more cement for the Channel Tunnel. In 1974 the boring machine for the channel tunnel was tested at Chinnor quarry, it is rumoured that it still remains in the hill today within a 210 meter long by 5 meter diameter tunnel. The quarry eventually closed in 2000. The land was acquired by Taylor Wimpey and the works demolished. All that remains today is a grade II listed Beehive kiln dating back to 1908 and the extremely blue water within the large quarries.

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Fig. 9. Chinnor cement works and Lime Kilns. 

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Fig. 10. Chinnor Quarry Today 

Flint

 

Flint originates in chalk (usually in the upper chalk layer). It is a hard form of mineral quartz occurring in various sizes and shapes. The flint outside is usually white with a rough texture and inside the flint has a glassy appearance and is usually dark grey, black, green or brown in colour. Often fossilised remains of marine organisms can be found in the cores of flint. 

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Fig. 11. Natural Flint Nodule

 

Flint has been used in the Chilterns since the early Stone Age for making tools (axe-heads/ arrow heads) and is believed to have been mined since the Neolithic period. However, the use of flint for building is not evident until Roman times and from then it is believed to have been in continuous use as a building material however the extent of its use and the status of buildings on which it was used has varied greatly over time.

 

Flint as a building material has limitations because of its irregular shape and size. It was traditionally used for rubble walling, with a more manageable stone or brick for the corners of buildings, and for window surrounds. In early medieval times flint was commonly rendered in lime externally. Evidence of this can be seen in areas of 12th and 13th century churches where minimal alterations and repairs have been carried out. Probably for this reason, examples are found incorporating a random mix of materials, some re-used.

Case Study 3: Fingest Church

 

Fingest Church, known as the church of St Bartholomew is a grade I listed building which can be seen from many of the surrounding hills. The church, which sits centrally in the village, is surrounded by an 18th century brick and flint churchyard wall, lined with ancient lime trees. 

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Fig. 12. Fingest Church

 

The key feature of the church externally is its huge Norman tower which was built in the early 12th century and is crowned by a twin gabled roof. The tower once held two bells, but only one of these remains, dating from 1830. The tower is built of flint rubble masonry which is rendered. It is believed this was the intended finish, and the dressings are of clunch and flint.

 

The plan of the church is unusual, with its large 12th century west tower being wider than its narrow nave of the same period. The present chancel, which is almost completely continuous with the nave, is a 13th century addition. Late in the 14th century a new window was inserted in the south wall of the nave, while those in the east and south walls of the chancel belong to the early years of the 15th century. In 1866 a large restoration project took place, when many details were renewed and the present south porch was erected.

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Fig. 13. Plan of Fingest Church

 

As this practice ceased, the quality and appearance of flintwork became more important.  By the 14 century flint began to be knapped (pieces or nodules split to explode the internal flat smooth surface). As time went on flint work became more decorative and towards the end of the 14th century into the 15th century flint work was carefully selected, coursed and graded with flint nodules being fully knapped (shaped) into squares to fit together like bricks. However this was a highly skilled and costly process some reserved for finer buildings, such as churches. However by the 16th century church building had declined and flint began to be used more widely in domestic buildings. Chequerwork, used on churches in the 15th century percolated down into domestic buildings.

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Fig. 14. Unknapped Flint

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Fig. 15. Knapped Flint 

 

Towards the end of the 16th century and into the 17th century timber-frame construction began to go out of fashion and brick construction was favoured. Timber framed buildings then began to be encased in brick and flint, with brick being the predominate material and often being used alone on the front elevation.  

 

In the 18th century, landowners favoured high quality flint work, particularly knapped and squared flints for their estate buildings and structures in landscape garden designs. 

Case Study 4: West Wycombe Park; The Mausoleum

 

West Wycombe Park, owned by the Dashwood family and often known as the Dashwoods Estate has a number of estate buildings and landscape structures constructed of flint. The mausoleum is a particularly interesting example of 18th century knapped flint work.

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Fig. 16. Exterior view of the Dashwood Mausoleum

 

The grade I listed mausoleum, which sits on the summit of West Wycombe Hill, was built in 1765 and houses the urns of the Dashwood family. The mausoleum is an unroofed hexagonal structure, formed by a series of linked triumphal arches. The structure is built almost entirely of local flint, which has been knapped with dressings in Portland stone. The main body of the mausoleum is not coursed flint, however careful control of the flint provides detail and dressings especially around the openings and then as the flint rises above the string course, it courses to provide clear bands and a neat topping to the structure. 

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Fig. 17. Interior view of Dashwood Mausoleum 

 

The use of flint here is flamboyant and can be read as a statement of the possibilities of using flint as a decorative and structural material. It is structures like these on the West Wycombe Park that inspired the other nearby estates to utilised knapped flints. 

In the late 18th and early 19th century, brick production increased, and the emergence of unknapped flints being used in conjunction with brick rose for modest domestic buildings. This is because thick beds of flints overplayed the brick earths, therefore the material was abundant.

 

The 19th century was the heydey for flint, and flint-with-brick became the predominant Chilterns ‘style’ that we know today. There was however an emerging contrast between ‘polite’ and ‘vernacular’ buildings. Many smaller houses, cottages and farm buildings were built with rubble flint facings tied to backings of brick. 

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Fig. 18. Image of traditional 19th century brick and flint building

 

 

Clay

 

Brick and tile-making in the Chilterns is known to date back to the 13th century. Extensive deposits of clay-with-flints overlay the chalk bed rock of the Chilterns. In places, this clay has been eroded to form a marly composition (a lime-rich clay soil). This marly soil is ideal for brick-making; its wide distribution throughout the Chilterns is reflected in the large number of historic brickworks. Locally produced chiltern bricks were nearly all red because of iron oxide in the clay, however differences in clay type and impurities affect the characteristics and colour of the bricks ranging from those with orange tinges  in the south-west of the Chilterns to nearly purple bricks in the north-east. 

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Fig. 19. Chiltern bricks and tiles

 

Generally Chiltern bricks were handmade, with rounded edges, rather than the sharp and hard edge of modern machine made bricks. It was common to use bricks of slightly different colours to provide ornamental detail. Burnt headers (achieved by burning high potash fuels such as bracken or gorse in the kiln) were used to create patterned or chequer effects.

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Fig.20. Chequered pattern house 

 

By the 16th century, brick was also appearing in a supplementary role to other materials, for example in plinths to timber-framed buildings or as infill panels. Some buildings in the Chilterns have employed bricks as infill panels from the outset, however in the 16th and 17th century, they also increasingly replaced former wattle and daub panels with brick. Relatively narrow panels could employ herringbone patterns, but wider spans would tend to opt for more conventional coursed brickwork.

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Fig. 21. The Wards Radnage, Timber frame with brick infill. 

 

Into the 17th century disastrous fires in towns prompted a change from timber-framing to brickwork due to its fire-resistant qualities, (a trend no doubt accelerated by the Great Fire of London in 1666.).

 

Brickwork in the Chilterns tended not to be painted, throughout the Chilterns the visual and aesthetic qualities of the fired bricks were simply allowed to express themselves without recourse to further surface treatment.

 

 

Clunch/ Tottenhoe Stone

 

Where chalk has been cut from the ground and used for building stone it has come to be known as ‘clunch’. Clunch is a hard chalk material and is often used in the dressings of buildings, including churches. Clunch was mined from a seam of particularly hard chalk that ran all the way from the Chilterns of Buckinghamshire, through Bedfordshire & Hertfordshire and into Cambridgeshire. The location of the stone could be easily identified because a springline (a lie of water springs) formed where the stone occurred. The availability of clean water led to the establishment of small settlements along this line, with the Clunch being used as a building stone.

 

Totternhoe Stone is such an example of Clunch. It was extracted from the village Totternhoe in Bedfordshire, which sits on the hard seam of chalk noted above. Around Totternhoe there is  evidence of the stones use as far back as Roman times. However it seems that the use of the material halted after the Romans left until Norman times when it was once again used to the building of churches and castles. Totternhoe stone was suitable for fine carving and was highly valued for decorative work in the medieval period, and due to this can be seen in many churches around the region and in other important medieval buildings beyond the area such as Westminster Abbey and Windsor Castle. 

 

Totternhoe Stone is commonly used in combination with flint. 

Case Study 5: All Saints Church, Chalgrave

 

Church of All Saints is a Grade I listed church in Chalgrave, Bedfordshire. It is recorded that consecration of the church took place in 1219. 

 

The church is built of rubble and ashlar walls, the tower is massive with large angle buttresses and chequered walling of flint and Totternhoe stone and the chancel is built of Totternhoe stone with a chequers facing of flint and Totternhoe stone. The tower was commenced late 14th century, however due to a partial collapse of the top section in the late 19th century (which has never been rebuilt) it looks slightly strange.

 

During the 1930s a series of wall paintings dating back to the 13th century were re-discovered in the church and later conserved.  

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Fig. 22. All Saints Church, Chalgrave

Timber

 

In medieval times, woodlands were the biggest natural resource of the Chilterns. They provided construction materials for houses, carts and fences, as well as all the fuel and heating. Many medieval timber-framed buildings, built of oak or other hardwood species survive today. 

 

By the 18th century Chiltern woodlands had grown in economic importance and were being managed. They were an important source of firewood, this was cut from the smaller trees, while other trees were allowed to grow tall to provide timber for construction.

 

By the 1800s the demand for firewood from Chiltern woodlands had fallen because more people were using coal for fuel in their homes. At the same time though the local furniture-making industry was taking off, and this required a regular supply of wood. Chair-making became an important industry, especially around High Wycombe. The woods began to change in appearance as tall, narrow trees were grown to produce timber which could be handled easily by woodland workers and beech trees began to be planted, as the favoured timber in furniture making. The chair industry thrived for over a hundred years but declined at the end of the Victorian era as foreign timber began to be imported in large quantities.

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Fig. 23. 15th Century timber framed building, West Wycombe

 

Vernacular Buildings

 

The Chiltern Hills is now predominantly designated as an Area of Outstanding Natural Beauty. This means that it is controlled by the Countryside and Rights of Way Act 2000, which aims to conserve and enhance its natural beauty. The character of the Chiltern Hills comes not just from it’s rolling hills, fields and woodlands but also from its picturesque villages, farms and houses. 

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Fig. 24. Chilterns Village, Turville

 

The vernacular of an area comes from the materials used to construct the buildings, these historically would have been what was locally produced and natural found close-by. In the Chiltern Hills the materials locally available are flint, timber, bricks and clay tiles. These materials, which have a distinct ‘Chilterns’ character, allow the buildings to blend in with their surrounding and complement the countryside around them. It is this consistent use of local materials which has created the special and distinctive character of buildings and villages in the Chilterns.

Case study 6: Hambleden

 

Hambleden village is a traditional Chilterns valley bottom settlement, nucleated in form and compact due to the rising slopes on either side. The village is framed by the distant views on either side of the valley. 

 

Hambleden is one of the most attractive villages in the district, its character almost unchanged since the early 20th century with many of its traditional vernacular features retained. This is by virtue of the local authority planning and listed building control measures and the restrictive National Trust covenant which Hambleden has. The National Trust covenant seeks to protect the vernacular form of the buildings and control issues which are outside of normal planning control, the covenant means that the National Trust has control over any new buildings and external additions or alterations. Therefore the modern curse of uPVC use has not entered the village. 

 

The village is centred around the church and manor with the village square bounded by cottage gardens proving an attractive nucleus to the village. The small Hambleden brook runs through the village, with an attractive bridge over the brook at the entrance to the village. 

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Fig. 25. Image of Hambleden Village

 

The cottages at the core of the village, are medieval in origin and sits tightly within small plots, they are predominately 1.5- 2 storeys, with a number of brick chimneys, dormers and gables which all add to the interest of the varied roofscape. The randomness of building plans and variety of building sizes creates diversity of facades which adds to the attractiveness of these vernacular cottages. However although the cottages are varied their material palette is similar and it is these traditional materials, techniques and architectural forms which add to the overall charm of the villages when they are read as a group.

 

The church, which sits in the centre of the village, dates back to the 12th century (although mainly rebuilt in the 14th century). It is constructed of flint with clay roof tiles.

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Fig.26. Image of Hambleden Church

 

The Manor House, which sits opposite the church at the centre of the village was built in the early 17th century and is of flint with brick dressings.

 

Hambleden is picturesque, the Chilterns geology has defined the shape of the village and the local Chilterns materials have determined the architecture of the place, making it truly a perfect Chilterns village. 

Although the design of the architecture within the Chilterns has varied over the years, the materials have remained the same since at least Norman times. 

 

Historically there was often no clear edge between town and country. The scatter of cottages and the soft interface between the village and surrounding woods and fields would have retained the sense that the village was part of the countryside and the traditional small scale buildings in the Chilterns would have enabled this blurring of the boundaries. 

 

The traditional archetypal style of the Chilterns emerged from the 17th century onwards with the combined use of brick and flint (with the occasional timber-frame). This style of houses in the Chilterns was rarely more than two storeys in height (with the upper storey partly in the attic with small plain rendered dormer windows), roofed with plain clay tiles and were often gable-ended. The buildings were rarely more than one room deep and adopted a 'T' or 'L' shape in order to minimise the span of the roof.

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Fig. 27. Traditional brick and flint chilterns cottage

 

Towards the 19th century this style developed and terraces, some of considerable length and uniformity, built of brick and flint became a common style of dwelling for estate houses. 

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Fig. 28. Bennett End, Radnage Cottages

 

The traditional materials of local brick, plain red clay tiles and flint are very durable and give a familiar character to a building. During the last 100 years the use of standardised items and non-local materials has started to become common, and in places this is affecting the character of the Chilterns.

 

However, the majority of the Chilterns still remains picturesque, with its villages and hamlets settled into the form of the landscape. I hope this article has inspired you if you live locally or have the opportunity to visit the Chiltern Hills, to take some time to explore the area and look out for its vernacular buildings and use of local materials. 

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Fig. 29. Picturesque chilterns view

Bibliography

 

Pevsner, N. and Williamson, E. (1994) The Buildings of England: Buckinghamshire. 2nd edn. London: Penguin Books. 

 

Chilterns Conservation Board, Chilterns Management Plan

 

Chilterns Conservation Board. (2006) Chilterns Buildings Design Guide-Chilterns Brick

 

Chilterns Conservation Board. (2003) Chilterns Buildings Design Guide-Chilterns Flint

 

Chilterns Conservation Board. (2007) Chilterns Buildings Design Guide-Chilterns Roofing Materials

 

Chilterns Conservation Board. (2010) Chilterns Buildings Design Guide. 2nd. edn.

 

Chilterns Conservation Board. (2019) Chalk, Cherries and Chairs; Landscape Action Plan 2019-2024

 

Chilterns Conservation Board, Buckinghamshire County Council and English Heritage. (2010) The Making of the Chilterns Landscape

 

Jackson, C. (2000) Radnage: Millennium Edition. Great Britian: Unity Print Ltd.

 

Anonymous Aston Rowant Resident (unknown) Chinnor Chalk Pits, Found At: https://astonrowant.wordpress.com/chinnor-chalk-pits/

 

Congregation and friends of All Saints Church Chalgrove, A brief guide to All Saints, Chalgrove, Bedfordshire, Revised 2002

 

Urban Design Division. (2003) Conservation area character survey; Hambleden