Preventing Decay in External Joinery

The risk of decay in exterior windows and doors has been recognised for many years. However, in the late sixties and early seventies the incidence of reported cases of decay increased dramatically, particularly in five to seven-year old houses. This was seen primarily as a problem related to the change in timber quality: increasing quantities of timber that contained a high proportion of sapwood were being used by joinery manufacturers and this material was more susceptible to decay. To deal with this situation preservative treatment was introduced as a standard part of the production procedure. However, preservative treatment should not be viewed as a substitute for good design and workmanship to which special consideration should be given in order to obtain high quality and lasting performance in joinery components. This digest describes the measures that can be taken to minimise the risk of decay. It replaces Digest 73.