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Historic Building Investigations

Timber Stress Grading & Identification

Visual Stress Grading of Timbers

Visual stress grading allows a means of assessing the strength of a timber in situ. EBS Ltd carries out a visual grading of the timbers classifying then into GS (C16) or SS (C24) grades according to the rules described in BS 4978: 2007 (Softwoods) and BS 5756: 2007 (Hardwoods). The knot area ratio, slope of grain, growth ring spacing and defects such as splits and bark pockets are identified then a grade is assigned to the timber.  Where a timber can only be seen partially a grade is given to that section only.

Engineers and designers converting existing buildings often want to know what load the existing timbers can carry.   The process requires that the full length of the timber to be assessed is visible with no paint finishes.

Timber Species Identification

The timber strength is dependent on its species. In order to assess the timber species a small sample of the timber is removed to allow the gross anatomical features to be assessed. Microscopic inspection may also be carried out to allow inspection of the anatomical features which are compared with published literature or known samples.

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