Medieval Buildings Archaeology

In Hampshire over 107 medieval timber-framed buildings survive and have been successfully tree-ring dated, between AD 1250 and 1530 (Miles et al. 2007, online); 95 of which have been surveyed as part of this project. The Hampshire Dendrochronology Project has been one of the largest and most extensive thus far undertaken in the British Isles” (Miles 2003b, 220). Key events with regard to the preservation of historic buildings and the built environment that have conserved such a rich corpus of buildings are listed below. This list refers to Hampshire and the rest of the country and includes the Town and Country Planning Acts of 1944, 1947 and 1968. These acts provide various legislations for “buildings of architectural or historical interest”, in order to provide a means to mitigate further losses (Gerrard 2003, 110), by making the owners responsible for their maintenance (OSPI 2009, online). This also grew out of a desire to keep the landscape intact, in the face of rebuilding and development, following the need to re-house and expand following the wars  (Gerrard 2003, 110).

Table 4 Key events with regard to the preservation of historic buildings and the built environment

Date

Event

Outcome

1877

Society for the Protection of Ancient Buildings (SPAB) founded

 

1885

Hampshire Field Club and Archaeological Society founded

 

1895

National Trust founded

 

1908

Royal Commissions on Historical Monuments for England, Wales and Scotland founded

 

1932

Town and Country Planning Act

Extends provision for local authorities to set up preservation schemes to protect inhabited buildings and groups of buildings including their surroundings

1941

National Buildings Record established

 

1944 & 1947

Town and Country Planning Acts

As part of a wide-ranging package of planning measures, provision made for compilation of comprehensive list of buildings worthy of preservation, the owners of which were required to give notice to the relevant authorities of their intention to alter or demolish them

1952

The Vernacular Architecture Group (VAG) founded

Regional based studies concerned initially with classification of building types, roof construction and the study of lowland and highland variants

1953

Historic Buildings and Ancient Monuments Act

The Minister of State, advised by the Historic Buildings Councils, empowered to order grants for repairs and maintenance of buildings of outstanding interest and their contents

1968

Town and Country Planning Act

Alters position so that owners of listed buildings wishing to demolish or alter them have to seek explicit permission for this, rather than serving notice of their intentions. Spot-listing introduced. Crown buildings listed for the first time

1969-1987

 

Resurvey of historic buildings for listing; interwar buildings first listed in 1970

1971

Town and Country Planning Act

Further powers granted, including compulsory purchase

1974

Town and Country Amenities Act

Toughens protection of Conservation Areas by requiring that demolition or radical alteration of buildings within them be sanctioned by relevant planning authority

1980

National Heritage Memorial Act

Appoints Trustees authorised to give financial assistance for the acquisition, preservation or maintenance of land, buildings, or structures deemed important to the national heritage

1984

English Heritage formed

They take over the role of Historic Building Councils and Ancient Monuments Boards

1990

Planning (Listed Buildings and Conservation Areas) Act

The basis of current law and legislation

1994

Planning Policy Guidance note 15 (PPG15) Planning and the Historic Environment

Major Government restatement of conservation policy, including buildings

Table based on (Hunter 1996, Appendix p191-3)

 

The study of medieval buildings has always sat between the disciplines of archaeology and art-history. This is due, in part, because both documentary evidence for buildings, especially those of a higher status, and the standing building itself, survive. The building, when studied in an archaeological context, can tell us as much about its architectural elements as of the social history of the people that built and lived in them; if we know how to read them properly (Morriss 2000, 10). This though, according to Richard Morriss, has only been acknowledged since the late 19th century (Ibid.). Prior to this, Morriss describes the study of ancient buildings as being one of ‘pure’ architectural history. That is to say people were more interested in the aesthetics of the building, than its social history (Ibid.). This changed in 1877 with the founding - by William Morris - of the Society for the Protection of Ancient Buildings (SPAB) (Anon 2009, online). Morris promoted the “link between art and society, between style and culture, between architecture past, present, and future (Crook 1984, 555). The Victorian period (1837-1901) saw the forming of many local history and archaeological societies following in the theme set by SPAB. One such group is the Hampshire Field Club and Archaeological Society. They were formed in 1885 and have “always been actively involved in the study of historic buildings” (Hantsweb 2009, online). The proceedings of the club have played an important role in providing research on various medieval timber-framed buildings and joints for this thesis. They claim “the Society was founded principally to forward the study and appreciation of Natural History, Archaeology and History within the County and to encourage the preservation of buildings and other historic remains of importance.”(Anon 1980, inside cover).

Vernacular architecture is defined by Brunskill as being that of a more local style, built by local craftsmen from local materials; as opposed to the politer form of national styles (Brunskill 1993, 21-4). Brunskill gives vernacular the alternative title of ‘folk’ housing and polite he classes as being ‘academic’. He suggests that whereas the former follows local tradition and needs, the latter tends to pursue “academic styles understood by a cultural few whose home is wherever an international cultural movement is accepted” (Ibid., 22). To paraphrase Brunskill, it could be said that vernacular architecture represents the working classes who build utilitarian architecture based on function. Polite, however, tends to be the preserve of the elite and powerful and is built in formal architectural styles that promote conformity, power and wealth (Ibid.). Richard Harris takes the definition further, suggesting that architecture is similar to grammar and, that although the people of England tend to speak English, there exist regional ‘vernacular’ dialects, within the umbrella of the parent language (Harris 1989, 1). He also suggests that both vernacular grammar and architecture are “cultural activities devoted to a practical end” (Ibid.). In Figure 3, Brunskill has set out a map showing what he believes are the various regions of Britain sharing vernacular traits, with area 1 representing the south east, of which Hampshire is a part (Brunskill 1993, 133). Because the aim of this thesis is to ascertain any changes in carpentry styles, between 1250 and 1530, in Hampshire, the study has drawn on evidence from both types of architecture to more fully understand how carpentry evolved, and why, over this period. Therefore, any differences between social levels could also be observed. This could help answer the question: Did the academically trained architects influence the local builder?

 

vernacular distributions

Figure 3 A map showing Brunskill’s "vernacular divisions of Great Britain"
(Brunskill 1993, 133)

 

Some important publications relevant to this research include the works of Nikolaus Pevsner (1951-74, and published more recently by John Newman (various dates)) and the joint works of Cyril Fox and Lord Raglan on Monmouthshire Houses (Fox and Raglan 1951, 1953, 1954). Of particular note here is Pevsner and Lloyds’ Hampshire publication, of 1967, in which they describe some of the more polite and religious buildings of Hampshire that were surveyed as part of this research (Pevsner and Lloyd 1967). In the introduction to the Hampshire book, Pevsner writes “in a county so poor in good building stone, it is odd that no major use was made of TIMBER. There are no really interesting timber-framed houses at all” (Pevsner and Lloyd 1967, 29-30). This research suggests otherwise, with several key buildings located in Hampshire including the earliest known hammerbeam roof – The Pilgrims’ Hall, Winchester (1295) – and the earliest known Wealden type house – 35 High Street, Winchester (1340) (Roberts 2003, 251 & 250 respectively). Such volumes demonstrated the value of detailed comparative studies, on a regional level, to understand the evolution of plan forms and structural techniques (Sheppard 1966). This was also the primary reason for the founding of the Vernacular Architecture Group (VAG) in 1952, to promote the study of the “lesser traditional building” (VAG 2009a, online). The group began publishing a peer reviewed journal, Vernacular Architecture, in 1970. This journal is still published annually and has proved an invaluable resource during this research project. The journal covers the whole of the British Isles and has, more recently, switched focus from general studies to a more regional one, including many articles relating to buildings of Hampshire.

One of the first academics of note to write a general review of buildings during this period,  was W. G. Hoskins, in his book The Rebuilding of Rural England, 1570-1640 (Hoskins 1953). Hoskins suggested that many of the buildings of the Middle Ages were rebuilt in the Elizabethan and Jacobean periods, based on the decline of the open hall and the insertion of a fireplace (Hoskins 1953; Platt 1994, 229; Quiney 1994). More recently the work of Edward Roberts has shown that Hoskins’s dates of 1570 to 1640, for the demise of the open hall, is not the case in Hampshire (Roberts 2007, 17). Roberts was able to use dendrochronology, not available to Hoskins, to create a precise chronology of buildings which show the last house built in Hampshire with an open hall was in 1533 at 56-8 Winchester Street, Overton (Roberts 2003, 242). Roberts’s work clearly illustrates the need for accurate chronologies and the reinvestigation of past theories, in the light of recent advances in dendrochronology, a sub aim of this thesis.

‘The dating of timber-framed buildings was revolutionised from the early 1960s by Cecil Hewett’ (Gibson and Andrews 1998, online). Cecil Alec Hewett (1926-98) is widely regarded as the key name in joint chronology and typology and his work will form a major focus for this thesis (Gibson and Andrews 1998, online). His two major publications, The Development of Carpentry 1200-1700: an Essex study (Hewett 1969) and English Historic Carpentry (Hewett 1980a), have been the starting point for this research. As the titles suggest though, Hewett’s main area of research has been, primarily, in the South-eastern county of Essex. Even so, his work is still the main starting point for anyone undertaking research into the field of timber framed buildings; reflected in the bibliographies of those that follow him. In the introduction to both books (Ibid.) Hewett gives credit to a Frenchman, Henri Deneux (1874-1969) as being the true pioneer of joint typologies (Hewett 1980a, 1). Although Deneux’s work focused on French ecclesiastical buildings, rather than English ones, his work was really the start of such investigations (Gibson and Andrews 1998, online ; Hewett 1969, 21). Deneux published “L’Evolution des Charpentes du XIe au XVIIe Siẻcle”, in the French journal L’ Architecte, July 1927 (Deneux 1927) and, it is his attention to detail, and creation of joint typologies, that Hewitt pays homage to in the introduction to his main work (Hewett 1980a, 1). Deneux’s work was revisited, and republished, in 2002, showing its importance and relevance in today’s world (Collectif 2002). In this republished book, modern scholars have reappraised his work, in the light of dendrochronology, and recalibrated his chronologies, similar in essence to this project with regard to Hewett’s work in Essex, following the Author’s reinvestigation of some of Hewett’s key buildings, by both physical survey and desk based research. Hewett was also involved in the dating of some carpentry styles in Hampshire, including ‘King Arthurs Round Table’, from the Great Hall at Winchester, 15-16 The Abbey, Romsey and Winchester Cathedral. The results of his research will be looked at in greater depth, in subsequent Chapters, alongside the results of dendrochronology and, in the case of the round table, also Radiocarbon dating.

Hewett’s work, along with many of his contemporaries, tends to reflect the surviving ecclesiastical and high status, politer buildings of the middle ages. This is shown by some of Hewett’s other publications, English Cathedral and Monastic Carpentry (1974) and Church Carpentry (1974); what separates his work, from theirs, is his detailed study of joint types.  J. T. Smith wrote a review on Hewett’s English Cathedral Carpentry (1975) which describes Hewett’s style of ‘3d’ illustration as being a great improvement over purely linear presentations (Smith 1978, 365). Hewett used a technique of hatching and shading to create the illusion of dimension, although Smith is unhappy about the lack of scaling from such techniques. Hewett’s aim however, was to illustrate chrono-typologies over individual case studies. This project has taken Hewett’s style of representing joints one stage further, by using 3d software to create computer generated models that allow the viewer to ‘see’ into the joint, to better understand its inner complexities as shown in Figure 4. Beyond this, as the models are solid entities, they can be animated to show the sequence of construction, as will be shown in later Chapters.

 

Hewetts scarf jointHaddleseys Scarf Joint
Figure 4 A comparison between Hewett’s line-drawn illustration of an Essex scarf and the Authors rendered 3D model of a Hampshire scarf

 

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2.1      The dating of medieval timbers

This Section will explore dating techniques available to the buildings archaeologist, from the height of Cecil Hewett’s work on historic carpentry, the 1960s and 70s, to the present. Alongside this, the evolution of such techniques and their integration into archaeological methodologies will be explored. The ability to date buildings with a high degree of accuracy has obvious advantages within building archaeology. Key events, such as the Black Death, happen over such a short period - only 2 years - that the ability to identify a buildings date of construction, before or after such an event, can have huge ramifications. J. T. Smith suggests that inscribed dates are the “surest evidence”, though warns, “they do not exist before the sixteenth century” (Smith 1970, 239). Smith also notes that documents can be unreliable, as they often relate to a plot of land rather than the building upon it, and therefore, it is difficult to identify the actual building to which the document refers (Ibid.). Alternative methods were needed in order to date buildings before the sixteenth century.

As a result, the development of secure chronological data has always been at the forefront of archaeological theory and research, and this has led to the testing of various dating methods (Truncer and M. Pearsall 2008, 1077). These methods include, among others:

  • typological dating (by style) – see Section 2.2.1
  • Radiocarbon dating (14C) – see Section 2.2.2
  • dendrochronology (tree-ring dating) – see Section 2.2.3.

These three methods will now be examined, in detail, and their usefulness in dating timber buildings analysed. On the subject of dating Hewett wrote: “[Radiocarbon dating] is a valuable but very expensive method, and [dendrochronology] is not yet available to the extent that is desirable. How useful these methods will become has yet to be established, and typological assessments that have due regard to the technological typology herein proposed are the best method available at the present time” (Hewett 1980a, 2). It is Hewett’s typological dating method that will be examined first.

 

2.1.1 Typological dating

Johnson defines typological studies “as local descriptions and classifications of house types, building materials and techniques, and decorative styles, with the intention of producing controls over dating and regional variation” (Johnson 1990, 246). Within the wider definition given above subsists joint typologies – i.e. the dating of buildings based on the timber joints used to construct them. This was pioneered in England by Cecil Hewett. When Hewett published his major work, English Historic Carpentry, in 1980, 14C dating was expensive and unreliable and, dendrochronology was yet to be established, in northern Europe, as a reliable and inexpensive alternative (Hewett 1980a, 2). Because of this, scientific techniques were not widely utilised by scholars at the time and thus, dating by type and technological progression were the only reliable techniques. This assumes that an ‘archaic’ joint is replaced by a more efficient one, and so forth and, that when a new joint is created, it is immediately employed by all carpenters introduced to it (Hewett 1962, 240). On this Hewett wrote: “in many instances different forms of the same joint are seen, and these can be arranged in such orders as give them the appearance of constituting evolutionary sequences, by way of which it may be assumed the joint has attained the form in which it is most familiar in our time”(Hewett 1962, 240). Hewett’s translation of Henri Deneux, regarding the dating by type and style, reads: “by examining all these examples of frame-work we have been able to prove, despite their great variety, that each period is characterised by definite assembly-methods” (Hewett 1968, 80).

The certainty, by which Deneux, Hewett, Smith and others date buildings, purely by style, is based on 20th century human assumptions, about work carried out over four hundred years previously: the validity and, more importantly, the accuracy of which, needs reassessing where possible, by the recalibration of such chronologies with recent scientific methodologies. These methods will now be discussed.

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2.1.2 Radiocarbon dating

Radiocarbon dating works by measuring the known decay rate of 14C (its ‘half-life’) which is known, against 12C which remains constant, following the death of an organism (Andrews and Doonan 2003, 136-7). Radiocarbon dating then measures the ratio between the known rates of decay of the 14C relative to the stable 12C; this is then used to calculate the date of death of the organism – in this case wood (Ibid.). The 14C is bombarded by 14N through cosmic radiation in the upper atmosphere. The interaction with nitrogen atoms produces 14C which is radioactive –i.e. its atoms are unstable. In the atmosphere, the unstable 14C mixes with stable 12C, present in CO2 (Radiocarbon dioxide) and is finally absorbed by the living organism, through biological processes such as eating and photosynthesis, at “a fairly constant proportion” (Andrews and Doonan 2003, 136; Baillie 1982, 223). One problem is that this form of dating, without subsequent calibration, tends to give a wide date range of approximately a century. This is due to varying amounts of 14C in the atmosphere, at different times, caused by factors such as solar flares, sun spots and the earth’s magnetic fluctuations (Andrews and Doonan 2003, 137; Baillie 1982, 224). Accurate dating can also be compromised by the presence of contaminants in the sample, when examined at a laboratory; usually caused during the collection process (Kovar 1996, 427).

Willard Libby (1908-1980) pioneered the science of Radiocarbon dating, during the 1950s, earning him the Nobel Prize for Chemistry, in 1960.  It is one of only a few scientific processes purely developed for archaeological purposes, in contrast with many other techniques borrowed from external disciplines to fit archaeological science (Andrews and Doonan 2003, 134). Radiocarbon dating is best suited for the chronological analysis of organic materials, predominantly charcoal (Libby 1961, 609), up to <50,000 years old and, therefore, is particularly useful to prehistorians (Baillie 1982, 223).

Godwin wrote about Libby’s work, suggesting that he was trying to seek the potential of using science to check historically, or stylistically dated, medieval timber architecture and to review “monuments of uncertain or controversial date for correct placement into chronology” (Godwin 1970, 71). He highlights problems in using this technique to date the timbers due to possible contaminates and the fact that tree-ring dates had to be used to calibrate the dates (Ibid.). The recalibration was based upon tree-ring dates obtained from bristle-cone pine chronologies (Libby 1970, 18). However, Godwin does suggest that a potential for its use did exist at the time, although dendrochronology has replaced any potential that Radiocarbon dating may have had in this field (Godwin 1970, 71-2). This is due to the greater accuracy and reliability possible with dendrochronology (Grenville 1999, 2). Conversely, by calibrating the Radiocarbon curve, using dendrochronological data from other trees, wood that cannot be dendro-dated can now be dated with greater accuracy by Radiocarbon dating (Haneca and Cufar et al. 2009, 1). Tree rings are also used “to confirm the veracity of other chronometric dating techniques, including archaeomagnetic, obsidian hydration and luminescence dates as well as chronologic sequences derived from seriation and stratigraphic analysis” (Nash 2002, 243).

Walter Horn, along with Ernest Born, used the Radiocarbon technique in Hampshire, in 1965, to try and date the original structures of the barns at Beaulieu-St. Leonards (Horn and Born 1965). Horn later published a recant of his work there by saying his results gave “cause for humility” (Horn 1970, 84). He went on to say: “Beaulieu-St. Leonard’s is only one of a considerable number of other buildings that could be cited to show what tricky problems this type of timber architecture poses to our efforts of dating” (Ibid., 86).

The tithe barn, that once stood at Beaulieu-St. Leonards, is believed to have been the largest of its type in England and is thought to have stood from the first half of the 13th century, until around the second half of the 17th century (Ibid., 84-5). Other examples of Radiocarbon dates obtained from timbers in Hampshire include:

  • 9 Great Minster Street, Winchester (Keene 1985a, 588)
  • Faccombe Netherton (Goodall 1990b, 92)
    • Originally 14C dated by the British Museum to the 12th or 13th century, the timbers are in fact late Saxon (c. AD 900)
  • King Arthur’s Round Table, from the Great Hall at Winchester (Biddle 2000)
  • Old Minster, Winchester Cathedral Green (Biddle and Kjølbye-Biddle 2002)
  • Winchester Cathedral choir stalls (Tracy 1993, 194-5)
  • Winchester College shutters (Biddle 2000, 217)

Some of the Winchester examples will be examined in greater detail in the concluding Section of this Chapter (Ch. 2.3).

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2.1.3 Dendrochronology

Horn was aware that for Medieval archaeology, the Radiocarbon data was flawed and suggested instead that “there can be no doubt that for ultimate precision we must turn to dendrochronology”, though he adds “in England dendrochronology was at the time of our gathering still in its beginning stages” (Horn 1970, 82-3). It is to the science of dendrochronology that the next Section is dedicated.

Dendrochronology (dendro-dating or tree-ring dating, as it is commonly called) is a combination of three Latin words: dendron = tree, chronos = time, logos = the science of, and is, therefore, the science of measuring time in trees, or “the study of tree time” (Nash 2002, 243).

Haneca suggests that, in order for dendrochronology to be effective, the following criteria must apply:

  • There must be anatomically distinct growth rings.
  • The trees should grow under a wide ecological and geographical range. This implies that the tree species can be found over an extensive area, in different types of woodland or forest.
  • The trees should be able to adopt a (co-) dominant position in different types of woodland. Dominant trees are more likely to respond to climatological pulses that often prevail over larger areas, whereas suppressed, or shaded, trees are more influenced by the local forest dynamics.
  • The heartwood should be sufficiently durable to ensure preservation of the wood.
  • The wood of the tree species should have been extensively used over a long period of time. European oak corresponds well with these requirements and is mainly represented by pedunculate (Quercus robur) and sessile oak (Quercus petraea) (Haneca and Cufar et al. 2009, 1).

It is a multidisciplinary science that can provide:

  • behavioural information
    • it can suggest how woodland was managed (silviculture); indicated by the speed of a tree’s growth and age at felling.
      • A faster grown tree indicates human intervention and management, as does excessive re-growth of branches, which in turn affects the tree’s anatomy (Haneca and Cufar et al. 2009, 7; Howard 1995, 226)
  • chronometric data – dendroarchaeological time sequences, object and building dates
  • environmental data – climate change, rain fall, atmospheric contaminants and ground water purity (Nash 2002, 243).

Dendroprovenancing can also be added to the list as an emerging development, in dendrochronology, that enables researchers to provenance timber and, thus, infer trade links; an area of study that has benefited, recently, from a more complete European chronology (Haneca and Cufar et al. 2009, 6; Haneca et al. 2005; Sass-Klaassen et al. 2008).

 

The science

The basis of dendrochronological dating is that trees of the same species, growing during similar time frames, in localised habitats, will produce similar growth-ring patterns (Baillie 1995, 17). These patterns, of varying growth-ring widths, are unique to the period of growth, similar to a human finger print (Ibid.). Once measured they can be matched against a “master chronological sequence”, of known tree-ring dates, with 95% certainty (Millard 2002, 137). This ever growing ‘master chronological sequence’ makes oak dendrochronology, in particular, a “dynamic and constantly evolving discipline” (Haneca and Cufar et al. 2009, 1). Each year a tree gains another ring as it grows, by adding a layer of cells; the thickness of this ring depends on the amount of growth in that year. These cells grow in the cambium layer, directly under the bark (Smith 1985, 19) (Figure 5). Thus, the older rings are located toward the heart of the tree and the younger rings, in the sapwood, near the bark (Tyres 1999, 2). The heartwood is recognisable as being much darker than the sapwood (Figure 5) because it is, essentially, dead wood and much harder than the softer sapwood (Grenville 1999, 10; Wilson and White 1986, 13). English oak will take approximately 15-50 years to turn from sapwood to heartwood  (Hillam et al. 1987). Sapwood tends to remain at a constant width, as the tree grows, whilst the heartwood continues expanding in size, as the sapwood dies (Wilson and White 1986, 14). New growth takes the form of widely spaced cells, formed in the spring and, closer, smaller cells during the summer (Taylor 2005, online). During years of ideal growing conditions, trees will produce a constant sized ring, whereas in a year with poor conditions, such as too much rain, wider growth rings will form, suggesting that “European oaks prefer mild and wet winter months” (Haneca and Cufar et al. 2009, 3).

oak rings

Figure 5 The anatomy of an oak tree and its ring pattern
(Haneca and Cufar et al. 2009, 4)

Trees growing in similar regions are likely to display the same general chronological growth pattern which tends not to reflect any localised ecological variations but, rather, the climatic variations (Miles 2005, online; Taylor 2005, online). Thus, over the life of a tree, various sized rings will create a “fingerprint” unique to that tree but, common to all other trees in that area, subject to the same weather patterns (Miles 2003b, 228). As weather patterns vary across Europe it is becoming possible, with an ever increasing master chronology, to provenance the timber and shed light on its source and, subsequent, trade (Haneca et al. 2005, 269; Sass-Klaassen et al. 2008, 97). When a tree is felled, or dies, the rings no longer grow; the final year of growth recorded using the outermost ring, directly under the bark (Miles 2003b, 220). In the United Kingdom, oak (Quercus robur and Quercus petraea) provide the best examples for dating, though elm and beech can also be dated (Baillie 1982, 45; Grenville 1999, 9; Miles 2003b, 221). This is of particular use to medievalists as the majority of timber framed structures were made from oak (Miles 2003b, 221). Oak wood is valued for its mechanical properties and its durable heartwood. It has been widely used since prehistoric times and is also, therefore, the leading species in historic, and pre-historic, tree-ring research in Europe (Haneca and Cufar et al. 2009, 1). Counting the rings will give the age of the tree but, unless the rings can then be matched against a known chronology, they cannot provide a method of dating the tree (Tyres 1999, 2). It should also be noted that tree rings can only provide a date for the timber and not the artefact, building or object (Haneca and Cufar et al. 2009, 8).

In order to obtain a dendro-date a collection of core samples need to be taken, by skilled technicians, from several timbers within the structure (Miles 2003b, 220; Morriss 2000, 142). The core is usually extracted by drilling the timber with a hollow drill bit, approximately 10mm in diameter (Figure 6 and Figure 7). However, the original method would have been to take a slice of wood; impossible from a standing structure (Baillie 1982, 93). This produces a cylindrical core, the length of which depends on the thickness of the timber, which contains a sample of the inner heartwood, out to the sapwood (Morriss 2000, 142). When taken back to the dendro-laboratory, the sample core is mounted and sanded smooth so that the rings can clearly be seen (Figure 8). The rings are then measured under a microscope and the data entered into the computer. The computer then compares the new data with existing chronologies, from an established “master chronology” dataset, within a specialist statistical software package and, statistical analysis run, to test for significance and correlation coefficient (Baillie 1995, 20-1; Miles 2003b, 220; Morriss 2000, 142). “The correlation coefficient is calculated at every position of overlap between the specimen ring pattern and the master pattern” (Baillie 1982, 86-92; 1995, 17). Providing the cores have a good date range and, more importantly, some sapwood rings, a date range can be arrived at and, in some cases, where the sapwood rings are intact, a specific felling date can be given (Baillie 1995, 21; Miles 2003b, 220; Morriss 2000, 142).

Oak tends to be used “green”, that is to say, freshly felled, as is it still soft and easier to fashion into desired lengths and shapes, for the crafting of joints (Biddle 2000, 390; Salzman 1952, 235). Therefore; the construction phase can be dated to within several years following the felling date, providing rings from the sapwood survive (Miles 2003b, 221). However; it is also possible to form an argument for storage of timber at a merchant’s yard, especially for planks and furniture making prior to purchase for construction. As opposed to felling followed by immediate construction; though the latter is by far the most common method at the vernacular level (Biddle 2000, 390; Eckstein 2007, 54-5).

 

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History of Dendrochronology

Dendrochronology, with regards to archaeology, was pioneered in North America, by A. E. Douglass, during the first decades of the 20th century (Bannister et al. 1998, 307-8; Haneca and Cufar et al. 2009, 4). Baillie suggests that, although tree rings had been mentioned prior to Douglass, it was he who was able to “establish its techniques and procedures and to build the first long chronologies which are the backbone of the science” (Baillie 1982, 27). Initially, there was resistance to dendrochronologies, as archaeologists and palaeobotanists were fairly sceptical that a meaningful chronology could be established in an unstable maritime climate, such as the British Isles (Baillie 1982, 93; Hillam 1979).  Douglass’ initial work was in dendroclimatology, in which he established “a method of estimating rainfall by the growth of trees” (Douglass 1914). He later added to this by publishing a c. 1,200 year long pine chronology which enabled him to date around 40 Pueblos (Native American settlements) in the southwest USA (Douglass 1935). This early work, however, did not use oak (Quercus robur and Quercus petraea) but, instead used the following: Douglas fir (Pseudotsuga menziesii) ponderosa pine (Pinus ponderosa) pinyon pine (Pinus edulis) Rocky Mountain juniper (Juniperus scopularum) and the giant sequoia (Sequoia gigantean) (Ferguson 1970, 183).

Some of the earliest work in England was undertaken by A. W. G. Lowther during the 1950s (Lowther 1951). He established a 13th century skeleton plot, spanning AD 1200 to 1300, based on oak timbers from Westminster and Hampshire (Schove and Lowther 1957, 83).  Lowther suggests that during this period “the visual matching of curves in dendrochronology is not generally acceptable, and, indeed, it is often regarded as an art rather than a science”, though it could be “found to be correct if more laborious mathematical tests were applied” (Ibid., 82). However, it was not until the late 1960s that dendrochronology came of age, as a science, in Europe, during the excavations at the Viking settlement of Haithabu, Hedeby, in Germany, by Eckstein (Eckstein 1969). The site provided one of the first opportunities to study and date oak-framed buildings, using dendrochronological techniques (Eckstein 1969; Eckstein 2007, 57; Haneca and Cufar et al. 2009, 4). Also, work carried out in Hampshire by an American dendrochronologist named Aldos Cortez Barefoot, was crucial in advancing the dating method in Great Britain during the 1970s (Barefoot 2000, 150). This, he achieved by creating a Winchester reference curve for the period AD1051-1972 (Barefoot 1975; Barefoot et al. 1978). John Fletcher then used Barefoot’s Winchester chronology, to add to his own research on oak boards to create an early chronology for the south of England (Fletcher 1977). It was not, however; until the late 1980s that the UK had its first full oak chronology. This was established by Mike Baillie in 1988, when he produced a full oak chronology in Ireland dating back to 4989BC (Baillie 1995, 11, 18). Following on from Baillie’s work David Haddon-Reece took various data sets and combined them “together with a suite of up-to-date programs [1990] and data in a computerised database” accessible to other dendro-chronologists (Barefoot 2000, 183). This fairly recent chronology is the main reason for the absence of precision dating in Hewett’s various published works, from 1962 to 1989, and one of the main reasons why this thesis aims to apply these known dates, to Hewett’s chrono-typologies, that were unavailable to him when he conducted his research. Fletcher wrote on this matter suggesting “may we not also hope that some of Hewett’s important timbers of late Saxon times in Essex barns and elsewhere can be accurately dated? Although lack of a long enough run of rings remains a limitation, the provision of samples now presents, perhaps, more problems than their matching” (Fletcher 1980, 38).

As the master chronology continues to grow, a re-evaluation of Hewett’s work is now a viable research project. This thesis aims to address this issue, as is so far possible in 2009, and to recalibrate his work, in order to shed new light on its current significance.

Dendrochronology has seen a huge increase in its accuracy and reliability, since Hewett’s initial work, and now enjoys a wide range of advocates; “…only one technological advance has really made a breakthrough in actually increasing our knowledge about the dates of buildings, and that is dendrochronology” (Morriss 2000, 142). Furthermore, Grenville suggests, dendrochronology can be used to give absolute dating and “is similar in essence to the prehistorian using Radiocarbon dating [14C] or the pottery specialist using thermo-luminescence” (Grenville 1999, 9). Clearly, dendrochronology has been one of the most significant advances in our understanding of dating timber-framed houses. As the corpus of dendrochronologically dated buildings increases, so too does the accuracy of the master chronology (Roberts 2005, 66).

 

The future

Advances in chronologies, and their dissemination coupled with advances in computing, optics and data acquisition, promise an exciting future for dendroarchaeology (Haneca and Cufar et al. 2009, 8). It is now the turn of digital archaeologists to help take the study and visualisation of these timber-framed constructions forward (Chapter 3). Now we have the science of dendrochronology at our disposal, we can couple that data with survey data and create meaningful datasets, coupled with Cartesian coordinates, to help answer theories and questions about medieval carpentry. These are the types of questions which drive the rest of this thesis.

More recently, the labour intensive method of counting and measuring rings, through a microscope by hand, has been semi-automated by a computer operated, optical imaging, device that can measure the rings and record the data directly (Conner et al. 1998; García-González and Fonti 2008). Another recent application to the science was pioneered, in Japan, which now makes it possible to undertake non-destructive, dendrochronological investigations on wood (Okochi et al. 2007). The method involves utilising images, taken by soft X-ray radiography and micro-focus X-ray computed tomography (CT scans) obtained from various wooden artefacts (Ibid., 159). The paper examines the use of both techniques, to obtain images of the rings and cell structures, without the need to physically extract samples. Their conclusion was that it was an effective methodology; however, its cost and immobility means that it is not,, presently, an economically viable alternative to drilling, though it is hoped this will change in the near future (Ibid., 162).

All text Copyright Richard Haddlesey 2011

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