The impact of internal checking on the log and timber value of fire salvage ash type sawlogs

Following the Victorian wildfires of 2005/06 and 2009, sawmillers reported abnormally high levels of internal checking in the timber from Victorian Ash fire salvage logs, causing a loss in timber value due to the reduced yield of appearance quality products.

This project examined internal check development and severity throughout the air seasoning period in slabs sawn from fire salvage sawlogs compared with slabs cut from normal ‘green’ logs.

The research did not uncover any significant difference in the spatial pattern, timing and severity of checking between the samples. However, internal checking did cause a measurable difference between the timber grade yields and values. The difference was due to a very large proportion of the checks in the green timber samples closing up in the last stages of air drying and during reconditioning. This trend was observed to a much lesser extent in the fire salvage samples. This points to the possibility that the ability for internal checks to recover is inhibited or damaged in timber sawn from fire killed trees.

The research shows that block stacking and plastic wrapping for two months to retain and equalise moisture content significantly reduced the incidence of internal checking, compared with normal open yard air drying. If the cost can be kept under $100/m3 then the increased value of the timber should outweigh the cost. Even without time in plastic wrap, air drying in more controlled conditions would increase the value of the finished timber by $48/m3.

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