Dendrochronology
Scientists and scholars of various disciplines have been using recent advances in dendrochronology, or tree-ring dating studies, in the Northeast along with the development of regional master chronologies for various species of trees to promote the dating of timber framed buildings and other buildings that have timbers somewhere in their construction. Although the science of dendrochronology was first formulated about 1905, it has only until very recently, perhaps since 2000, that the science has gained much popularity with private homeowners. Before that time, the science, art and philosophy of dendrochronology – aka – dendro-dating – was mostly limited to the determination of ages of buildings under the control of certain public and some private institutions. However, the home owner is becoming more and more interested in knowing the exact dates of construction of both their houses and their barns.

The oak slice from the Taylor stone Lancashire style ground barn located just west of West Chester in Chester County, Pennsylvania was dendro-dated to 1752. This date established the structure to be the earliest basically intact and scientifically verified barn in all of Pennsylvania.

The oak slice from the Tredyffrin double log crib English Lake District style bank barn located near Devon in Chester County, Pennsylvania was dendro-dated to 1779. This barn type is an extreme rarity in Pennsylvania.

Dendro-dating can be a very effective although not foolproof way of creating data that can often lead to discerning the age of construction of various buildings and structures in the northeast and beyond. There are, however, certain criteria that must be satisfied or met in order that a wood testing on any particular building will yield good to even excellent but not guaranteed results.

This small 3 by 5 inch hemlock brace from a barn in western Massachusetts has a remarkable 270 annual growth rings making the average width of each ring extremely narrow. (Photo courtesy of Shaun Garvey.)

The field grown Sacred Oak in the Oley Valley in Berks County, Pennsylvania has been connected to Native Americans for hundreds of years. Fully intact slices of tree trunk would yield hundreds of annual growth rings. The tree is called a chinquapin or yellow oak. The tree is now thriving under the wonderful care of a new owner.

Criteria for Wood Samples as Good Candidates for Dendrodating
Not all wood samples from timber frames or other beams in various buildings and structures are good candidates for dendrodating. There are four basic criteria that must generally be met. They are the following:

The first criterion is that a waney edge must be present in the obtained wood sample – either a core of wood or slice of wood. Wane is the area of wood that was immediately adjacent to the bark in a tree. Wane is significant as this was the last annual growth ring to be deposited, so to speak, before the tree was felled. If, by using the method of dendro-dating, it can be determined when the outermost ring was formed the possibility exists that the construction date of a timbered building might be determined.

The second criterion is that the wood sample can not be so infested with powder post beetle that the proper “bulk” of wood is not present. In addition, the wood can not be so deteriorated by other destructive agents that the wood bulk is affected. Ultimately, what must be present in the wood sample is a “clear path” of good wood (often straight path) from the waney edge to the center of the tree or pith. This path can theoretically be as little as about one-half inch in width. Beyond the pith the condition of the wood is immaterial. In fact, the wood sample can be cut off just beyond the pith and not affect the dendro-dating work.

The third criterion is that the wood sample must cross date well. An explanation of this phenomenon is very involved. Suffice it to say it is related to a number of environmental factors. Not all wood samples with good waney edges and that are not infested turn out to cross date well.

The last criterion is seen where dendro-dating is used so that a timber framed building may be dated, that is, when the construction occurred – where there is the assumption that the timber or tree the wood sample came from was felled the year (or perhaps one to two years) before the structure was erected. The other requirement was that it was used in the original construction of the building, that is, not recycled.

If all of these basic criteria are faithfully met, then it may be said that the building was very likely constructed the year (or possibly the second year) after the timber or tree was felled. Again, there is no guarantee that the science of dendro-dating will absolutely yield or reflect a time of original construction of any timbered building.

           

Costs of Doing Dendrochronology
Eastern Barn Consultants will determine what costs are involved in the dating of a particular building and this information will be given to a prospective client. It is imperative to know that the stated costs will be in full effect assuming that good and proper wood samples may be obtained. In the process of extracting wood samples in the past there would have been occasions when a good sample could not be obtained. This may be for a number of reasons. Good cores, and not too often wood slices or sections may be extracted in their “full form.” Occasionally a few attempts are made to extract cores or slices from the same beam. If this is the case, other attempts are made to extract cores or slices from other beams in the same building. Some buildings do not yield good cores even if a prior determination has been made that a certain beam or beams in a specific building is (are) likely good candidate(s). In this eventuality, Eastern Barn Consultants must still charge for the effort to obtain a good sample. If more than one building is to be dendro-dated on the same day, that is, cores or slices to be obtained, then there will be charges for the first building. If attempts fail for the second building then there will be a separate charge. This charge applies to certain geographic areas. Areas beyond about 50 miles from the home base will dictate different charges depending on the area.

Proviso
Eastern Barn Consultants specifically does dendro-dating work for purposes of general information only – that is – for the general interest and curiosity of its clients. The company can not assume responsibility for any subsequent damages of any kind that may result from the determinations of establishing a supposed felling date for a timber or timbers that were incorporated into a building. The felling date or dates, determined by a lab deemed reputable by Eastern Barn Consultants are then used for a likely date of construction of a building within about 1 to 3 years after the date of felling. However, and most importantly, there is no absolute guarantee that the “apparent” date of construction determined by dendro-dating was the actual construction date of the building or structure in question. A client may or may not at his own discretion base a historic restoration or renovation of a building on the determined dendro-date of a building. Therefore, the client is expressly told by Eastern Barn Consultants that they should consult a professional architect versed in historical buildings and their construction techniques what era of construction should be the basis of a restoration or renovation. Eastern Barn Consultants can not be held liable for any subsequent damages of any kind at any time that involves any work by anyone hired directly or indirectly by the client of Eastern Barn Consultants who may rely on the “established dendro-date”.

Gregory D. Huber