ABSTRACT
Due to the critical problems of wood rot in exterior panel structures, several research projects have been started in the Nordic countries in order to prevent damage of this kind. The moisture conditions in a panel are crucial to determining the risk of wood rot, unless impregnated wood is used.
Presented here is a laboratory computer-based method for monitoring the moisture conditions in a test panel during a specific climate cycle. The test panelling consists of five boards with nails, joints and overlaps. To measure the moisture ratio distribution, an electrical resistance method with fourteen measuring points is used. All of the probes are connected to a computer which monitors the moisture conditions at hourly intervals. The climate cycle consists of a rainfall phase and a drying phase. The method makes it possible to determine the capacity of a paint or a paint system to keep a panel in good condition.
More than forty paneled structures painted according to different paint systems have been studied by this method. Panels from old structures, painted in a way found to be inadequate, were used as references. System painting, by which a coating is built up in several layers, each with its own purpose, has given the best results. It has also been shown that treatment of the end grain with the priming system is crucial.
