The most important parts of a timber structure are usually the parts you cannot see: bearing ends buried in masonry, the hearts of large beams, plates behind finishes.
How it works
A resistance micro-drill drives a very fine needle into the timber and records the resistance it meets. Sound timber, decayed timber and voids each produce a distinctive trace, giving a profile of the member's internal condition through its full depth, from a hole little larger than a woodworm flight hole.
Why it matters
Without this evidence, decisions about structural timber default to pessimism: cut out what cannot be proven sound. Micro-drilling replaces that guesswork. Members that would once have been condemned can be shown to be sound; genuinely decayed material can be identified precisely and repaired locally.
Micro-drilling in practice
At Bodmin Jail, micro-drilling of the Governor's Hall roof demonstrated the principal timbers were generally sound, with decay confined to contact points with masonry, enabling a targeted repair scheme that retained the historic structure. At York House, micro-drilling formed part of the timber investigation within an award-winning conservation project.
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