Since 1983 an environmental improvement programme has been in progress in the city of Dundee. This programme included the erection of rail and pale timber fencing throughout the city. The timbers had been pressure treated with CCA prior to painting with 2 coats of an exterior wood stain finish. However, the larger dimension timber fence posts (100 x 125 x 1500 mm3) regularly developed severe checks/shakes in service. These defects raised questions regarding the continued use of timber as a fencing material by the municipal authoritiy due to concerns relating to the long term efficacy of preservative treatment and timber durability. Statistical models generated from visual and physical measurements of aged post timbers recovered from field sites in the city indicated that a reduction in the development of structural defects was associated with lower heartwood:sapwood ratios. The sites from which posts were recovered also influenced defect development indicating inconsistent timber quality specifications and/or pronounced variation in environmental conditions at each site. This paper highlights the problem of many municipal authorities who, through lack of available information, fail to implement specifications for treated timber components tailored to their specific requirements.

Download document (604 kb)
free for the members of IRG. Available if purchased.

Purchase this document