Bodmin Jail: Governor's Hall

Assessing concealed timber without destroying fabric.

SMT Associates was commissioned by C Field Construction to investigate the principal roof timbers of the Governor's Hall and areas of timber decay within the floor structure below.

Our investigation combined detailed inspection, resistance micro-drilling, timber moisture measurements and laboratory analysis of mortar samples. These techniques allowed us to assess concealed timber condition at masonry interfaces, establish moisture levels and investigate the causes and extent of deterioration.

What the evidence showed

Testing demonstrated that the principal roof timbers were generally sound, with localised decay where posts and braces contacted the masonry. Separate investigations identified significant dry rot damage to wall plates and joist ends beneath chimney breasts and defective rainwater disposal systems. The findings informed a targeted repair scheme designed to retain sound historic timber.

From diagnosis to repair

We prepared detailed repair recommendations and drawings covering local timber and resin repairs, securing opened roof-truss joints, and replacement of severely decayed wall plates and joist ends. Measures to address the underlying moisture sources included repairs to rainwater goods, investigation and repair of chimney details, and improved ventilation while maintaining fire separation.

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