Moisture transport through wood coatings: The unanswered questions

Abstract

For years there has been debate about the optimal permeability characteristics for the many types of wood coating now available. Some coatings stand accused of 'trapping' moisture; others make claims of allowing 'breathing' but may not control movement. The question therefore stands, 'is there an optimal band for moisture transport, for a given set of conditions?'. This paper reviews the evidence of past and more recent work and sets out to consider whether the issue can yet be resolved. A new Performance Standard for wood coatings is now nearing completion. It is thus vital that the question be answered to enable realistic performance criteria to be included in the specification. [This review is adapted from a paper first presented at the PRA Symposium 'Advances in Exterior Wood Coatings and CEN Standardisation' October 19-21 1998].