Dating building materials

I am not as convinced of its practicality, compared to say, a habitat for humanity store; this pile of knotty pine wall panelling is in Kansas City MO, on a site with listings from San Francisco to New York. Moving it is expensive, which is why reuse is usually a pretty local phenomenon.

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However they also do consulting. They worked with five demolition and reclamation contractors three not-for-profits and two for profit to procure and test the materials, sourcing close to the project to reduce fuel consumption and saving the project time and money. Can't get enough TreeHugger?

Sign up now and have it sent straight to your inbox. Daily and Weekly newsletters available. Email Address Email is required. Nathan Benjamin runs a dating service for materials, putting people together with the used. Related Content on Treehugger. Small carbon-neutral house in Australia built with recycled materials. Lofty eco-resort treehouse is built with locally sourced wood. Nevertheless, the laboratory was able to demonstrate many interesting properties of ring widths and their relationship with various aspects of climate and other natural phenomena and, of course, their use in the accurate dating of timber.


His laboratory is still one of the leading centres in world dendrochronology. It was not until that the science was taken seriously in Europe, mainly through the efforts of Professor Huber in Germany, and not until after World War II that such studies became established in the UK. The main centres in Britain researching this field are located at universities in Belfast, Cambridge, East Anglia, London, Nottingham and Sheffield with several freelance practitioners.

Whilst most dendrochronological research is still concerned with climatic change, where the precise dating provided by the growth rings is of vital importance, all units in this country are proficient in performing dendrochronological surveys of buildings. Oak is the species of prime interest and it is possible to date wood back to over 7, years with a precision, in appropriate circumstances, of a single year. This is most impressive and makes dendrochronology the main dating method for structures containing oak timber. The method relies upon the response of trees to the weather during the growing season, which runs from March to October.

In a 'good' growing season the trees within a large climatically homogeneous region all respond by putting on a wide growth ring within the cambium which separates the sapwood from the bark. In a 'poor' growing season the trees all respond so that only a very narrow growth ring is formed. In more typical growing seasons a ring of intermediate width is produced. It should be noted that there is no direct linear relationship between ring width and, say, sunshine, or other weather components Thus a 'good' or 'poor' growing season is defined with reference to the amount of growth produced.

For example, the year had a gloriously hot, long summer with most rainfall arriving in autumn but the trees did not appreciate it and all oaks produced a distinctively narrow ring. Again the summer of was cold and wet, quite different from , yet the trees also produced a distinctly narrow growth ring. So it will be seen that seasons that are hot and dry as well as those that are cold and wet will produce a narrow ring so that such a ring is not diagnostic of the weather.

Year by year the trees throughout the region produce a similar pattern of wide and narrow rings in response to the weather changes. It is this pattern that allows the accurate dating. The pattern of ring widths on a specimen taken from a building is matched, using a computer with a 'master chronology' often several centuries long for the particular area. This regional chronology will have been painstakingly built up from many thousands of measurements and by cross-matching many overlapping patterns of timbers.

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The youngest patterns are obtained from living trees, where the felling date of the final ring is known. Progressively older patterns are obtained from trees in recent buildings, older buildings, archaeological sites and ancient bog oaks. Because of local, non-climatic causes of change of growth width, the chronologies around the country vary somewhat, and the best dating match is always obtained from a local regional master chronology. The dendro-date is thus the year in which the final ring of the specimen grew the year in which the tree was felled, but not necessarily the year in which the building was constructed.

In order to obtain an accurate match and hence a date, it is important to have at least 80 rings on the specimen that is to he dated. With fewer rings the pattern might have repeat matches at different points in the time scale and so give rise to multiple possible dates. This has implications for some vernacular structures in which rapidly grown, wide-ringed oaks, 30 to 40 years old, were used. In such instances it might be possible to date the wall plate which often contains far more rings.

In practice it is found that or growth rings are most likely to provide a unique match. However, because of the local ecological, non-climatic effects on the tree ring, it is not possible to guarantee that any particular specimen will give a date. In order to have greater certainty it is important to obtain several samples, in the form of cores drilled from the timber, and to construct a 'site chronology' for the building. The number of cores required will depend upon the complexity of the structure, but some ten cores per building phase is preferred.

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These are normally taken by the dendrochronologist in co-operation with the historian and the position of the cores is carefully marked on the building plan for future analysis of the results. The core leaves a small hole in the timber of about 15mm in diameter which may be plugged with a timber dowel. Although this method is capable of dating to the individual year, in practice several factors conspire to reduce the precision in dating the construction, sometimes drastically, and it is important to be aware of the limitations.

Whilst in the middle ages it was the practice to use the timber 'green' - usually within a year of the felling date - in more recent times the timber is usually allowed to dry out, sometimes for decades, before use. Furthermore, carpenters, aware of the effects of insect attacks, would deliberately remove the sapwood and even some heartwood.

The number of sapwood rings may vary between 15 and 50 years, depending on the position in and the age of the tree.

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Thus the year of the last ring dated could be misleading to the construction date and be underestimated by an unknown number, possibly 60 years. Sapwood may be found on at least some of the timbers in the dendrochronological survey and the site master chronology will lead to a more reliable date than an individual core.

Whereas tree-ring dating is limited in this country to oak structures, radiocarbon dating may be used for any wood species and, indeed, for any other organic based materials found in buildings such as: The range of radiocarbon dating reaches back to 60, years. For the last few thousand years it can have a precision of a few decades and may, in certain circumstances, be comparable with tree-ring dates. The laboratory at Cambridge here in England was among the first six to be set up anywhere in the world.

There are now several radiocarbon dating laboratories in Britain including those at Belfast, Cambridge, East Kilbride, Oxford and Swansea, as well as a commercial unit near Harwell. Radiocarbon dating is based on the element carbon, the basis of all life on earth.

Planet Reuse: A Dating Service For Used Materials | TreeHugger

The atoms of this element are of three different types or 'isotopes'. They are identical chemically but have slightly different physical properties, particularly in mass. The isotopes are respectively 12, 13 and 14 times as heavy as the common hydrogen atom the base unit by which the weight of other elements is measured. The isotopes C and C are stable and make up the bulk of the element, but the C isotope, which is mildly radioactive, is extremely rare.

The instability of radiocarbon results in half of it disappearing in 5, years its 'half-life'. This instability is the basis of the dating method. All creatures have the same concentration of radiocarbon in their cells while they remain alive. This level is maintained constant by a sequence of events affecting the food web.