A protective coating is often used on the cladding of wooden facades to limit the absorption of moisture. Low wood moisture content (MC) is essential to obtain satisfactory durability performance. Wood density is known to influence the water sorption and crack formation of uncoated wood. However, the effect of density on the aforementioned behaviors of coated spruce is not yet fully understood. Six-years of data on the crack formation and the MC variation of outdoor exposed panels are analyzed in this article. The outdoor test was complemented by a subsequent laboratory experiment, wherein the MC variation was monitored at different depths on the board during artificial water spraying. The aim of this research was to increase the knowledge about how wood density and aging affect the water sorption of coated spruce through the crack formation. The results indicated that wood density had an impact on the overall sorption behavior of coated spruce. Low-density spruce contributed to faster water absorption and desorption processes than coated samples with higher density. However, the observed correlation to density was limited to a condition with an intact coating. High-density characteristics contributed to more crack formation, and the density–sorption relationship reversed with a cracked coating. A cracked coating caused a strong local increase in the MC of the wood at the location of the cracks. Weather-exposed replicates without cracks had a higher MC in the core of the board compared with the value beneath the coating. The higher MC is probably due to the water sorption of the uncoated backside of the panel. Such an occurrence raised awareness for future studies to account for multidimensional sorption behavior from all sides of the panel. The local difference in MC also raises awareness for future studies to investigate local MC variations (as opposed to the global average of the panel) in research on the durability of coated wood.

The use of wood contributes to the global transformation into a bio-based community. There are, however, challenges. The growth of mold, rot fungi, and algae on the coated surface is of major concern due to decreased aesthetic service life and shorter maintenance intervals. The colonization of a coated surface requires the presence of spores, nutrients, and a sufficient amount of water. This work studied the influence of using heartwood and sapwood on the moisture content (MC) and growth of microorganisms on the surface of coated Norway spruce boards [Picea abies (L.) Karst.]. The results revealed a relationship of heartwood samples having a lower MC and a lower or equal degree of biological growth on the coated surface than sapwood samples. The relationship was valid through a range of densities (309–548 kg/m³) and two different coating systems based on either an alkyd or an acrylic resin. Furthermore, the choice of coating color (red compared to white) affected the MC as the red-colored samples had a lower MC, combined with no growth of microorganisms.

A multicycle Wilhelmy plate method was applied to study the water and octane sorption behaviour of small Norway spruce veneers. Dry heart- and sapwood samples of varying density were investigated. The results showed a correlation between the porosity and the sorption of octane for all samples, i.e. a higher wood porosity resulted in higher octane sorption. However, no difference in octane sorption was found between heart- and sapwood samples of similar density. The water sorption behaviour was difficult to interpret, probably due to the influence of surface-active wood extractives. It is suggested that the presence of such extractives, particularly in the sapwood samples, increases the sorption of water due to a significant decrease in its apparent surface tension. Hence, the results indicate that the liquid water sorption of spruce heart- and sapwood is strongly influenced by variations in the extractives content rather than by the micromorphology.

Conventional chemical wood preservatives have been banned or restricted in some applications due to human and animal toxicity and their adverse impact on the surrounding environment. New, low-environmental-impact wood treatments that still provide effective protection systems are needed to protect wood. Thermal modification of wood could reduce hygroscopicity, improve dimensional stability and enhance resistance to mold attack. The aim of this study was to investigate if these properties enhanced in thermally modified (TM) wood through treatments with oils. In this study, TM European aspen (Populus tremula) and downy birch (Betula pubescens) wood were impregnated with three different types of oil: water-miscible commercial Elit Träskydd (Beckers oil with propiconazole and 3-iodo-2-propynyl butylcarbamate, IPBC), a pine tar formulation and 100% tung oil. The properties of oil-impregnated wood investigated were water repellency, dimensional stability and mold susceptibility. The treated wood, especially with pine tar and tung oil, showed an increase in water repellency and dimensional stability. However, Beckers oil which contains biocides like propiconazole and IPBC showed better protection against mold compared with pine tar and tung oil. To enhance the dimensional stability of the wood, pine tar and tung oil can be used, but these oil treatments did not significantly improve mold resistance rather sometimes enhanced the mold growth, whereas a significant anti-mold effect was observed on Beckers oil treated samples.

Användandet av materialet trä i produkter är ett lån från naturen som förr eller senare genom nedbrytning av vedsubstansen ska återföras till det naturliga kretsloppet. Avseende användningen av solitt trä i produkter bestäms tidsperioden innan återföringen till naturen av produktens konstruktion och trämaterialet i sig självt i relation till den omgivande miljön samt användningen och hanteringen av produkten. En produkts förmåga att motstå, eller behålla sina egenskaper trots dessa yttre påfrestningar benämns dess beständighet.

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.

Wood material has advantages, it comes from a renewable source and it is easy to manage. But one disadvantage when used outdoors is biological discoloration of the material. Some impact on the discoloration is the presence of moisture and nutrients, necessary components for the microorganisms to grow and start a colonisation. Samples made of Norway spruce (Picea abies (L.) Karst) heartwood or sapwood coated with two different film forming paints was studied. The paints had a binder formula made of alkyd or acrylate. Additional parameters related to study the influence of moisture content on discoloration were high and low density material, with and without impregnation oil. Outdoor exposure was made during five years in the southern part of Sweden. The samples were hung with 45 degree inclination, facing south direction. Visual differences in biological surface discoloration were observed for samples within the same paint, which could be explained by differences in heartwood and sapwood.

From a legislative point of view it has been possible to build timber buildings with arbitrary number of storeys in Sweden during almost two decades. Several buildings up to eight storeys have been completed during that time, but the competence for planning and building such structures are limited to a handful of actors. This fact has been recognized by funders of research/education and an educational program for spreading the knowledge within the industry led by Linnaeus University is financed since about two years. Particularly interesting in the programme is that the courses are developed in cooperation between the industry and the academia. The courses are to fulfil needs with respect to knowledge, but also with respect to format so that the main target group, skilled engineers within the industry, can find the motivation to follow a course or lager parts of the program.

Storm-felled trees left in the forest for a shorter or longer period, affect the quality of the logs. The change in quality ismainly because of attack of fungi and insects, which in turn depends on the moisture content (MC) of the sapwood. Thepurpose of this study was to receive more knowledge about drying of storm-felled trees by investigating how fast winterstorm-felled Norway spruce and Scots pine dried when left in the forest. Sixteen storm-felled spruces with part of the rootsstill in ground contact were selected from three stands and in addition to 10 pines from one of the stands. The trees wereexamined for MC in the sapwood until 21 months after the storm. This study indicates that wind-thrown trees with rootsstill connected to the soil can survive one summer without any value loss caused by draught, fungi and insects. The standconditions can be of importance as the storm-felled trees in the stand, with scattered windthrow, were in best condition afterone year, as they were shadowed by the trees still standing. Comparing spruces and pines with the stand with scatteredwindthrow, pines were more sensitive to drought and reached critical MC earlier.