Dendrochronology Survey

Dendrochronology dating is a process by which construction dates, for a timber-framed building, can be calculated. By extracting a series of cores from timbers, an exact year or a close range of years can be statistically determined. Adrian Gibson submitted a request to English Heritage to make a dendrochronological survey of the St. Barnabas barn with the objective of answering two questions :-
    1. What is the date of the barn? From technical details it is thought to be have been built in the sixteenth century.

    2. What is the date of a distinctive group of arcade posts with rear shores, thought to have come from an earlier phase built in the mid fifteenth century?
English Heritage commissioned Andy Moir (Tree-Ring Services) to undertake the survey. Click here to see the results.
Original bark allows us to determine when the tree was felled.
Drilling with a hollow drill to take a core sample.
Removing the core from the drill.
The set of extracted cores.
Dendrochronology, or tree ring dating, provides an indication of when a timber-framed building was constructed, through an assessment of the growth ring patterns in a cross-section of the trunks of the timbers used. Variations in the thickness of the annual growth rings give a unique pattern for each tree species within a particular geographical region. (See anatomy of oak section).

Unique core sample configurations may be likened to a product bar code. A year with favourable growing conditions will produce a wider growth ring than a year with poor growing conditions.

By cross matching a core sample of a timber from an existing building with a master or reference chronology database (of say oak trees in East Anglia), scientists are able to determine when the timber was felled. If the section of timber still retains its bark this can be used to determine the year and even the season that the tree was felled.

Historically, oak timber was trimmed and shaped for construction purposes within a year of felling as the oak became harder to work after twelve months.

Core sanded to 600 grit for analysis

Further information on the taking of core samples, the limitations of the sampling techniques and the analysis of historic timbers by dendrochronology, can be found on the Building Conservation web site and the Tree ring web site.