Influence of some wood characteristics on the variation of moisture content in outdoor exposed coated Norway spruce panels

A field test of coated spruce was exposed outdoors during three years, measuring the influence of wood characteristics on the variation of moisture content in coated panels. Wood samples had following characteristics: fast-grown or slow-grown wood, heartwood or sapwood. Three different film-forming coatings were tested and all samples were exposed above ground on racks. The measured moisture contents were evaluated using the statistical method Principal Component Analysis (PCA). The moisture content of the coated samples was clearly influenced by wood characteristics; fast-grown wood had higher moisture content and higher moisture fluctuation than slow-grown wood in each respective coating system. The choice of coating system also affects the wood moisture content. The result indicates that in order to achieve low moisture content- excluding the effectiveness of coatings, wood characteristics should also be considered.