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The House History exercise – principles employed

1. Architectural surveys

As part of the Roots and development of Bingham study, funded by the heritage Lottery Fund, Trent and Peak Archaeology was commissioned to survey a number of buildings in Bingham. Each study employs the methodology developed by Trent & Peak Archaeology (TPA) for use on similar projects in the region. This methodology conforms to the standard requirements of planning authorities where consent applications are made for development, re-development, building conversion, major restoration or demolition. These follow guidelines to be found in the National Planning Procedure Framework (2012) which replaces conservation planning document Planning Policy Statement 5: Planning for the Historic Environment (PPS 5, Department for Communities and Local Government 2010).
The procedures follow closely those laid down in English Heritage’s Understanding Historic Buildings. A guide to good recording practice (2006). The methodology also accords with the Institute for Archaeologists (IfA) Codes of Conduct and Standards and the paper Standard and Guidance for the Archaeological Investigation and Recording of Standing Buildings or Structures (Institute of Field Archaeologists 2001).

2. Tree-ring dating

In most instances the building reports have been compiled in conjunction with separate dendrochronological sampling carried out by Nottingham Tree Ring dating Laboratory.

Tree-ring dating relies on a few simple, but quite fundamental, principles.
Firstly, as is commonly known, trees (particularly oak trees, the most frequently used building timber in England) grow by adding one, and only one, growth-ring to their circumference each, and every, year. Each new annual growth-ring is added to the outside of the previous year's growth just below the bark. The width of this annual growth-ring is largely, though not exclusively, determined by the weather conditions during the growth period (roughly March - September). In general, good conditions produce wider rings and poor conditions produce narrower rings. Thus, over the lifetime of a tree, the annual growth-rings display a climatically determined pattern. Furthermore, and importantly, all trees growing in the same area at the same time will be influenced by the same growing conditions and the annual growth-rings of all of them will respond in a similar, though not identical, way.
Secondly, because the weather over any number of consecutive years is unique, so too is the growth pattern of the tree. The pattern of a short period of growth, 20, 30 or even 40 consecutive years, might conceivably be repeated two or even three times in the last one thousand years. A short pattern might also be repeated at different time periods in different parts of the country because of differences in regional micro-climates. It is less likely, however, that such problems would occur with the pattern of a longer period of growth, that is, anything is excess of 50 years or so. In essence, a short period of growth, anything less than 50 rings, is not reliable, and the longer the period of time under comparison the better.
The third principal of tree-ring dating is that, until the early- to mid-nineteenth century, builders of timber-framed houses usually obtained all the wood needed for a given structure by felling the necessary trees in a single operation from one patch of woodland or from closely adjacent woods. Furthermore, and contrary to popular belief, the timber was used "green" and without seasoning, and there was very little long-term storage as in timber-yards of today. This fact has been well established from a number of studies where tree-ring dating has been undertaken in conjunction with documentary studies. Thus, establishing the felling date for a group of timbers gives a very precise indication of the date of their use in a building.
Tree-ring dating relies on obtaining the growth pattern of trees from sample timbers of unknown date by measuring the width of the annual growth-rings. This is done to a tolerance of 1/100 of a millimetre. The growth patterns of these samples of unknown date are then compared with a series of reference patterns or chronologies, the date of each ring of which is known. When a sample "cross-matches" repeatedly at the same date against a series of different relevant reference chronologies the sample can be said to be dated. The degree of cross-matching, that is the measure of similarity between sample and reference, is denoted by a "t-value"; the higher the value the greater the similarity. In turn, the greater the similarity the greater is the probability that the patterns of samples and references have been produced by growing under similar conditions at the same time. The statistically accepted fully reliable minimum t-value is 3.5.
However, rather than attempt to date each sample individually it is usual to first compare all the samples from a single building, or phases of a building, with one another, and attempt to cross-match each one with all the others from the same phase or building. When samples from the same phase do cross-match with each other they are combined at their matching positions to form what is known as a "site chronology". As with any set of data, this has the effect of reducing the anomalies of any one individual (brought about in the case of tree-rings by some non-climatic influence) and enhances the overall climatic signal. As stated above, it is the climate that gives the growth pattern its distinctive pattern. The greater the number of samples in a site chronology the greater is the climatic signal of the group and the weaker is the non-climatic input of any one individual.
Furthermore, combining samples in this way to make a site chronology usually has the effect of increasing the time-span that is under comparison. As also mentioned above, the longer the period of growth under consideration, the greater the certainty of the cross-match. Any site chronology with less than about 55 rings is generally too short for satisfactory analysis.

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