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Oxford Tree-Ring Labratory - Interpretation of Dates

Dating Web Site · Main · Videos; Cost of dendro dating advice So fault crowning to launch on a date, although fault bouncing port on a date. The fault in . A site which is to introduce tree-ring dating as carried out by Martin Bridge of the timbers - and therefore it is difficult to give an idea of costs for any given job. We want to measure tree ring width for growth analyzes. . In fact, with the cheap price of the software suite, is likely much better than the much more . measuring system and developed three site chronology in central Zagros, Western Iran.

The timber had a last measured ring date ofwith no evidence of sapwood, therefore an earliest possible felling date of was given. Unfortunately, this was presented on television as a felling date ofand used as evidence to suggest that the ship took part in the Armada. In reality, however, the felling date could just as well have been after During filming, it was stressed that the date was from a single timber; whatever the result was, it should be treated with extreme caution.

Regrettably, this was edited out of the final programme. The original painting was supposed to have been painted in When questions were raised recently as to whether it was painted by Rubens himself, or by a minor hand some years later, the National Gallery commissioned a dendrochronological analysis by the University of Hamburg of the oak panels upon which the painting was applied.

This was interpreted by some as supporting the claim that the painting could have been painted in What was not stressed was that the painting could just as easily have been painted in orbecause it is not really known how much of the outer heartwood had been removed from the tree in conversion.

Thus the dating neither proves or disproves a particular date after However, had the last measured ring beengiving an earliest possible felling date ofthen one could say that it was extremely unlikely to have been painted by Rubens in Alternatively, had the last measured ring date beenthen one could quite safely state that it was impossible to have been painted by Rubens in Again this illustrates some of the difficulties in dealing with samples without any sapwood. In presenting tree-ring dates, it is important to make it clear whether the timbers dated have complete sapwood, partial sapwood, or no sapwood at all.

Where a number of timbers have been dated from a phase, it is obviously those timbers which have given precise dates which are most relevant, and of those, the latest precise date is most likely to be nearest the actual construction date.

Where complete sapwood is not available and felling date ranges or felled after dates are offered, then a reference must always be given as to which appropriate sapwood estimate is used. The most important thing to remember whenever presenting a tree-ring date is that it is the felling of the tree which is being dated, not the construction of the building. This should always be made clear in any summary. Either a date can be presented as: One cannot say on dendrochronological evidence alone that a building was built in a precise year.

English Heritage is presently drawing up proposed dendro-chronology guidelines. Whilst different conventions may be required for presenting condensed results such as the Vernacular Architecture tree-ring date lists, these would be appropriate for most applications. The proposed conventions for the publication and quoting tree-ring dates are reproduced here in abbreviated form: This practice would have prevented many misquoted dates from being printed.

If the site is a particularly large and complex one, and the tree-ring dates are a fundamental part of the publication, then consideration should be given to joint authorship with the laboratory concerned.

What is Involved? - Martin Dendro

It has been considered to be a waste of resources to date buildings for which the building dates were already known. This is regrettable, for much can be learned by relating the felling date of timbers and the building accounts. Identification of the period intervening between the felling of the trees and the building date from documents should allow a greatly enhanced interpretation of tree-ring dates for other buildings.

Recent work has produced a number of tree-ring dates for which documentary dates are available. Stokesay Castle, for instance, has produced various felling dates of springspring and summerspringsummersummerand winter and spring from various parts of the Great Hall, North Tower and Solar cross-wing. Too few timbers had complete sapwood surviving to allow any trends in the phasing of the various elements of the complex to be detected, but instead suggest that all was under construction at one time.

A licence to crenellate was obtained in from Edward I, suggesting that much of the building work was under way. At Lodge Farm, Odiham, precise felling dates were obtained for both the hall and the cross-wing.

Whilst the Exchequer rolls covering the period do not differentiate the work on the Lodge from that being carried out on Odiham Castle, the rolls covering the period itemise clearly the work on the Lodge cross-wing. Analysis of the building operations suggest a construction period of about five or six months, with the rates being paid suggesting work being executed during the summer months.

Given that the two precise dates obtained indicate felling between October and Marchand that the Exchequer accounts cover the period up to Michaelmas 30 Septemberbuilding could have taken place during the summer months of or At Court Farm, Overton, we are fortunate in having both the house and the barn mentioned in the Winchester Bishopric Accounts.

The barn produced a felling date of late summer for one of the arcade posts, and a date of late spring for a joist found in the adjacent house, presumably a leftover timber from the barn. Therefore the Accounts suggest that the timber had been obtained over two different years, and it was in the first year that the principal timbers such as the arcade post which was dated to the summer was obtained.

It was not until after September that the rest of the timber was obtained, transported, trimmed and sawn, and framed. Two felling dates of summer and late spring were obtained for joists, and three struts and three collars over both ranges were all felled in the late spring of The Pipe Roll covering the period Michaelmas is missing, but the Roll for the year commencing 29 September shows payments being made for felling and trimming 30 oaks at Ecchinswell, six miles away, and for constructing six saw pits to saw the timber.

References are also made to 39 tons of timber being trimmed and dressed at Willesley, and as no reference is made to this latter timber being felled during the period of the Accounts, it is possible that the timbers which have been dated to late spring were obtained from this source.

During the period between Michaelmas and Michaelmasthe Accounts state that the old hall was pulled down, with some timber and tiles salvaged, and that brick foundation walls were constructed. Here, we have seven timbers, six of which have been felled in spring ofwith references suggesting they were converted during the period of September and September The framing was then carried out during the early months ofwith the building being tiled and doors and window shutters hung before the end of September Overton again features in another documentary reference for a house at Winchester Street, found in the rent collectors accounts from Corpus Christi College, Oxford.

Seven precise felling dates were obtained for this building: Although we do not have building accounts per se, we do know that one of the timbers was still part of a living tree in the spring ofand that the property was habitable and occupied by the end of Septembera period of fifteen months having elapsed between the two. Another example of documentary references tying up with felling dates can be found at the Abbots House, Butcher Row, Shrewsbury.

This an elaborate three-storied, jettied and carved townhouse on a corner site. This suggests that from spring to the ceremony in April the frame was being constructed off-site, and that the ceremony related to the construction of the stone foundation, but prior to the erection of the prefabricated frame on site. These examples of comparing building accounts with felling dates are useful in that we can see that usually one if not two years intervenes between the felling of the latest trees, and the dates recorded in the accounts.

That these buildings are all minor domestic or agricultural buildings also bears more relevance to the study of vernacular architecture when compared to major ecclesiastical or Royal buildings where different methods of obtaining and storing timbers may have occurred.

But even without the building accounts, the dendrochronology sometimes can give a good indication of the timing of the framing as well as the erection of a building. With such a large group of trees cut at the same time, the evidence strongly suggests they were felled for a particular project, and that they were converted almost immediately.

So why the late date for the king post? Other, non-documentary, comparisons can be found in inscribed dates or date stones. Whilst these are often found to commemorate purchases, marriages, or other non-constructional events, it is nevertheless useful to look at those which clearly relate to felling dates obtained through dendrochronology. Alkington Hall, Whitchurch, Shropshire, produced a felling date of autumnand has a date plaque of At the Old Manor, Chawton, a date stone of compares favourably with a felling date of winter Meeson Hall, Shropshire, produced two felling dates of spring and springand a carved overmantle contains an inscribed date of The slightly longer interval here may relate either to the fact that the trees dated may have been earlier then other, undated timbers, or that the internal fittings were completed later than the main structural shell.

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Golding Hall, again in Shropshire, has a dendro date of summer for a principal rafter, and a date stone of ; again the comments above would apply. Overall, the inscribed dates would suggest that the building dates are usually within a year or two of the latest felling date. These dates have ranged between one and thirteen years apart, and in one phase as many as six different dates were detected, but certainly short-term stockpiling is the most common.

Only primary-use timbers are included in the above statistics. The histogram below indicates the spread of dates in relation to different samples: Year apart range of complete sapwood dates over instances No. Thus, many sites do have timbers which have been stockpiled to a greater or lesser degree.

This figure illustrates how important it is to date precisely as many samples as possible from a single phase to allow a better interpretation of the construction date of the building. Half a dozen samples from varying elements of a building with precise sapwood dates all ending within the same year will strongly suggest a construction period within a year of the latest felling date.

On the other hand, if only one precise date is available, then the person interpreting the results may suggest a construction period several years earlier than may in fact be the case.

This still leaves a significant proportion of examples of samples being felled over a period of four years or more. It is really a matter of chance whether the single precise date was obtained from a timber felled just before the time of construction, or from old timber which had been stockpiled. Most dendrochronologists would present such dates as "felled and used in or shortly afterwards". The only almost certain way of determining whether a precise felling date obtained is representative for a phase of building is through replication, and using various types of structural members.

However, it is not always possible for the dendrochronologist to obtain more than one precise date, short of demolishing the structure. A building may be of such high status that the entire sapwood will have been trimmed off during conversion and working of the timbers, or subsequently during repair works. The building may have suffered the depredations of time, decay and beetle attack destroying the soft sapwood, or only a handful of timbers from a phase may survive or be accessible for sampling, etc.

Nevertheless, the dendrochronologist should never be satisfied with one sample with complete sapwood where there are others capable of being sampled. Unfortunately, dendrochronology is subject to monetary budget constrictions as is any other science, and this too is a limiting factor.

Timbers with varying dates can be found in a building phase for a variety of reasons. Trees might have died within the woodland, or have lain for some time as windfalls.

Continuous sequences of buildings or phases may result in smaller members such as studs, joists or rafters being left over and used in a later phase. A good example of this can be found at Court Farm, Overton, where the barn produced a single felling date ofwhilst in the house four timbers produced felling dates ranging from towith the sole exception of one joist dating fromstrongly suggesting this timber was left over from the barn.

Alternatively, timbers might have been obtained from different sources, which often would have been felled at different times and under different circumstances. This is particularly common in town buildings where timber would have been available from intermediate sources such as timber merchants; this diverse sourcing would account for the poor intra-site matching often found in urban situations.

It is also highly probable that carpenters and timber framers kept stocks of timbers left over from previous projects for use in future work. An interesting contemporary reference strongly supporting the above explanation of differing felling dates, is found in an account by John Lancaster, agent for Corpus Christi College. During his tenure in Overton during the period to circahe was responsible for the building of several houses, and in an account from he states he had 17 pieces of timber remaining on his hands from earlier work.

No doubt many other similar accounts and inventories exist which show that timber was a valuable asset and would have been retained for future work. Only rarely has deliberate stockpiling been detected. Although Shapwick House in Somerset produced only a single precise felling date, some of the principal rafters and collars showed incontrovertible evidence of having been cut to size, but then left to season for at least 5 years before their joints were cut.

This was apparent because the collars had severely distorted, but the tenons were perfectly true, proving that the timber was dry by the time the timbers had their joints cut Figure 8. It is unfortunate that this roof had been recently defrassed the action of chopping off sapwood liable to beetle attack so that the archaeological evidence of stockpiling could not be compared with dendrochronological evidence. The quoting of estimated most likely single dates, no matter how carefully qualified the statistics, should be discouraged.

Where no indication of sapwood remains, then only a felled after date, or earliest possible felling date, can be given. When the sapwood range was produced ten years ago, it was the best that could be produced based on the data available at the time. Histograms of over sapwood ring counts now suggests that this range for the British Isles is now too wide for England and Wales and that the upper end of this range could be significantly reduced.

More detailed revisions of sapwood estimates are presently being carried out, both by this laboratory as well as by Sheffield University, using the wealth of both published and unpublished data sets now widely available, and taking into account other factors in addition to simple numbers of sapwood rings.

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From this research it is hoped to be able to produce sapwood estimates which are even more substantially reduced. Evidence obtained by this laboratory suggests that instances of multiple felling dates within a phase of building are far more common than was previously thought, and that care should be taken to obtain as many complete sapwood samples from a particular phase of building as possible to correctly identify the latest actual felling dates and allow a better interpretation of probable construction dates.

Ideally, research budgets should be broad enough to allow the sampling of at least eight to ten timbers with complete sapwood if available. Caution is needed when using single felling dates when interpreting building dates, as the likelihood of them being one or more years out is high. Clearly it is vital that sufficient and accurate recording, interpretation of the structure, and phasing of the timbers is carried out at or before the time of sampling, and that this is made available to the dendrochronologist to precisely locate individual timbers.

If the building has been wrongly interpreted, the wrong timbers could be sampled, giving earlier dates for re-used timbers, or later dates for repairs or alterations. If only one or two samples are taken from a site, then this is a very real risk.

Unfortunately, in many cases, only a few samples are available to the dendrochronologist, and the interpretation must take this into account.

Ideally, detailed recording should be undertaken whenever a building is being dated, as the additional information apart from the date such as jointing details, framing and truss design, and decorative elements such as moulding profiles, chamfer stops, and window designs would be of immense value to future studies.

Examples of comparing precise felling dates with building accounts as well as date stones show that construction usually commenced within twelve months of the latest date of felling, rarely extending to more than two years. Again it is imperative that sufficient precise felling dates are obtained to correctly identify the latest date of felling, otherwise it is best to be circumspect when proposing construction dates. Finally, when presenting tree-ring dates in any sort of document, report, or publication, the user should always consult the laboratory and the dendrochronologist who produced the date with a draft.

This would ensure that what the user might consider to be a minor expendable phrase such as "not felled before" is not omitted. It must be remembered that it is the felling of the tree which the dendrochronologist is giving, not the date of construction of a particular building or object. Sampling usually takes between hours, the analysis and results then normally take weeks although this wait can sometimes be fast-tracked at an additional cost. Dendrochronology results are presented either as PDF files or printed full colour written reports, which generally include a floor plan and photographic record of sample locations.

Building dates are normally also published in Vernacular Architecture. This means that in the unfortunate event that samples cannot be dated you will incur no further charge. The English Heritage guidelines document on dendrochronology states that "Where possible, at least eight to ten timbers should be sampled per building or, for more complex buildings per phase".

To maximise the potential of dating a building phase we preferentially take 10 samples. Our prices remain keen. Live tree, veteran tree, or woodland analysis The only precise way to determine the age of a living tree is to cross-date tree rings in increment cores that intersect the pith of the tree. Timbers are sampled using a 3-thread, 5.

While the girth of our very largest trees and hence the trees of greatest interest may make it impossible to reach their piths with hand-driven increment borers, increment sampling still offers the most accurate empiric refinement to the estimation of a tree's age.

The total cost of tree dating analysis which includes call-out is: Professional reports The full colour illustrated reports explain the methods and results, and includes interpretation, discussion, a floorplan and photographic record of sampling locations.