From about 1760 to the end of the 19th century the structural timber used in UK and Irish buildings was mostly Scots pine (Pinus sylvestris) imported from the Baltic region of northern Europe. This timber came from trees that were several hundred years old when felled, and is generally considered to have a superior durability to the younger growth Scots pine now available.
The Conservation Wood project was devised, in partnership with the Office of Public Works in Dublin, to investigate this belief by evaluating the durability of home-grown pine for conservation repair and replacement. Home-grown timber is of interest because the trees will grow more rapidly than they will in colder northern latitudes, and there is often an available source close to the conservation project.
Durabilty of Scots pine
Early research with Scandinavian Scots pine seemed to demonstrate that core timber (juvenile wood) did not have the durability of the mature heartwood. If this was true then younger trees would always have a reduced durability because the proportion of juvenile wood (first 20 - 30 years growth) is going to be greater in a 50 year old tree than it is in a 300 year old tree. This problem was investigated by taking samples of sapwood, heartwood and juvenile wood from two different heights in each of three Irish trees of the same age (60 years) and subjecting them to controlled decay.
Analytical method
Samples were placed in chambers containing active dry rot (from an international culture strain and from a wild strain), and weight loss over three months was calculated. The results indicated that there was too much variability, both within the wood and within the rate of fungus colonisation, to draw any useful conclusions. Statistical comparisons could perhaps have been supported by a greater number of samples, but small trends have no practical value.
Wood chemistry
The effects of wood chemistry were investigated by cutting small samples from 200 year old tree trunks, analysing the variation in the phenolic chemicals thought to confer decay resistance across the trunk, and subjecting samples of known chemistry to dry rot. The chemistry was compared with samples of historic Baltic wood of known provenance. The results are still being evaluated.
