Structural Timber Testing
Historic timber raises two separate questions: how old is it, and how much of it is still doing its job. Dendrochronology answers the first by matching ring patterns against reference chronologies, often dating a roof or frame to within a year and sometimes to a season, which frequently rewrites what was assumed about a building's development. Decay and strength assessment answers the second using resistance drilling, probing and visual grading, distinguishing surface decay from loss of structural section. Both usually cost far less than the decisions they inform.
What this category covers
- Dendrochronology and tree-ring dating of historic timber
- Resistance drilling and micro-drilling decay assessment
- Visual strength grading of historic structural timber
- Species identification and conversion analysis
- Assessment of beam ends, joints and concealed timber
Tree-Ring Services
Tree-Ring Services is an independent dendrochronology laboratory based at Mitcheldean in the ...
Testing historic timber before you replace it
Establish loss of section, not presence of decay. Surface rot and beetle flight holes look alarming and frequently sit on timber with ample sound section behind them. Resistance drilling gives a profile of sound material, which is what an engineer needs to decide whether repair will serve.
Date before you alter. Dendrochronology needs suitable samples with sufficient rings and, ideally, surviving sapwood, and those samples are far easier to obtain before repair than after. A precise date frequently changes the significance of the structure, and therefore the consent position.
Understand what beetle evidence means. Old flight holes are a record of past infestation, not proof of current activity, and most treatment is applied to timber where the beetle left decades ago. Active infestation has its own indicators and, like rot, depends on moisture.
Use the results in the repair specification. Test results support minimal intervention: splicing a beam end rather than replacing a beam, retaining a member with a reduced load, or leaving historic timber in place with a discreet secondary support.
Questions to ask
How accurate is tree-ring dating?
Where enough rings survive and the sample matches a reference chronology, felling dates can often be established to within a year, and to a season where bark edge survives. Where sapwood is missing, results are given as a range with the estimate stated.
Is beetle damage in old timber a problem?
Often not an active one. Flight holes record past emergence, and infestation depends on moisture content. Assessment should establish whether beetle is currently active and whether structural section has been lost, before any treatment is considered.
Can a decayed beam end be tested rather than replaced?
Yes, and this is one of the most useful applications. Resistance drilling profiles the sound timber remaining, which frequently shows that a localised splice or a discreet support will serve where wholesale replacement had been assumed.
The business listed under Structural Timber Testing
- Tree-Ring Services Gloucestershire
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