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ABSTRACT
Predictions of the expected equilibrium moisture content (EMC) for timber are frequently made by reference to previously published 'relative humidity versus temperature charts,' which often give values founded on amalgamated data for a number of species. When applying such charts to specific species of current commercial importance, discrepancies can be substantial. This paper provides a summary of the results from a series of experiments to establish the EMC on an individual basis for a range of commercially important softwood and hardwood species used in the United Kingdom.
The purpose of the research described in this paper is to help overcome the well-known fact that mismatches between the equilibrium moisture content (EMC) of timber and the surrounding en vironmental conditions can result in a range of problems including movement, distortion, and warping (1-3,5). The movement of timber components inservice as a consequence of adsorption and desorption of moisture due to the installation of timber at inappropriate MCs is a significant cause of on-site remedial action. Any work that can add to the body of knowledge and minimize the risk of in-service disruption by providing more accurate data on the behavior of timber in certain environments will result in a reduction of remedial costs and enhance the consumer perception of timber as a building material. The aim of this research was therefore to produce individual sets of EMC values for various commercially important species (Table 1) for interior use in the United Kingdom. The background to the work and the experimental procedure were discussed in detail in a previous paper (2).
There are many sources of data that provide recommended average MCs for wood and wood-based materials (e.g., (11)). However, the salient aspect of this research that makes it different to other work determining EMC values is that of species specificity. That is to say that this work devotes itself to the assessment of species of commercial importance within the U.K. construction industry. The data are intended to provide EMC evaluations for specific species in environmental conditions representative of those expected in internal environments within the United Kingdom. It should be emphasized that even a few percent deviation from the collective average EMC may cause the problems associated with MC variations.
Furthermore, shifts continue toward...