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Assessment of Decay in Timber Beams

Feb 28, 2024

Using a RESISTOGRAPH Decay Detection Drill


This Landmark protected building structure had suffered from a long period of neglect. The lead had been removed from the gutters causing significant water penetration.  This resulted in saturation of the masonry in which the structural timbers were supported.  The structural integrity of the trusses needed to be assessed to establish the extent and type of repairs required.  

A RESISTOGRAPH decay detection drill was used to plot the extent of decay in the beams.


As can be seen from the following photographs the decay is not immediately apparent because a surface layer of sound timber hides the decay within the beam.




Decay hidden within the middle of a beam

The photograph below shows the decay in the middle of the beam, with a thin veneer of sound timber on the outer face.  This is dry rot which is very sensitive to air movement and desiccation.  It is trying to maintain the ideal environment to decay the timber away from sunlight and air movement leaving the surface veneer.  

The extent of the decay along the beam is governed by the amount of moisture available to the dry rot.  The dry rot is able to generate moisture, when digesting the cellulose, which can maintain the decay in the absence of desiccating air movement.  The decayed timber remaining is mainly Lignin.

In this case the maximum distance the decay extended was 1.5m along the beam from the wall surface.



Legal and Insurance claims

EBS Ltd has the expertise to establish the age of the decay and we are often instructed to determine this in legal and insurance claims.