Pithwell / Timber
What we can say about a timber
A tree-ring result is one of three kinds, and which one you get depends on what survives on the wood. Here is how to tell before you send anything.
What do you need from the owner?
Where the tree grew, what the timber was used for, and a clear photograph of any cut end with a ruler beside it. Say whether any bark edge or pale sapwood survives. We would rather hear the awkward details first: they decide which of the three kinds of result is possible, and whether to go further.
A result states how many rings were measured, which reference chronologies they were matched against, the match statistic, and which of the three kinds of date it is. If a timber cannot be dated, the result says that, and why.
How many rings are enough?
More is better. A long run of rings has fewer chance matches than a short one, so short samples are treated with caution. Reports from English Heritage’s Ancient Monuments Laboratory warn against relying on one timber with fewer than 100 rings. Several timbers from the same building, felled together, make a firmer date.
Source: dendrochronology reports from English Heritage’s Ancient Monuments Laboratory, held by the Archaeology Data Service. We have quoted them as a caution, not as a fixed threshold.
What is sapwood, and why does it matter?
Sapwood is the outer, living part of the trunk, and it is the first thing lost when a timber is trimmed. Oak sapwood has a limited number of rings, so if some survives, the felling date can be estimated. Published estimates for English oak run from about 9 to 46 rings, by region and period.
| Bark edge present | The felling year, from the last ring. |
|---|---|
| Some sapwood present | A felling range, from a regional sapwood estimate. |
| Heartwood only | A “felled after” date: the last ring plus the minimum sapwood allowance. |
Does a date tell you when a building was built?
It tells you when the tree was felled, not when the building was finished. Timber was often used soon after felling, but it could be stored or reused from an older building. A date is stronger when several timbers agree on the same felling year or season, and weaker when only one does.
A cored beam gives one felling date. Ten beams from one roof that agree give a roof.