This paper summarizes the test recommendations for selected semi-destructive testing techniques as developed by members of the RILEM Technical Committee AST 215 "In-situ assessment of structural timber". The recommendations cover resistance drilling, core drilling, glue line test, tension micro-specimens, screw withdrawal, and several hardness tests. The paper includes a matrix of common non-destructive testing to assess structural timber. The discussion of each technique is intended to provide users with sufficient information to understand the theoretical basis, typical equipment set up, and basic capabilities and limitations

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The aim of this paper was to analyze selected properties of beech wood (Fagus sylvatica L.) treated by one-sided surface charring. Specimens were one-side charred with a hot plate using several time-temperature combinations (from 200 to 400 °C). Characteristics such as colour, discoloration, surface roughness, fire resistance, total carbohydrate content at several wood layers and decay resistance were evaluated. Surface charring was applied to the radial and tangential surfaces. Colour measurements showed that the surface of the wood turned grey due to charring. In addition to colour measurements, other experiments showed significant differences between radial and tangential specimens due to their different structures. The higher the temperature used in treating them, the lower the roughness values for radial specimens, while the trend for tangential specimens was the opposite. A smoother surface is more fire resistant, so radial specimens are generally better in this regard. Tangential specimens are more susceptible during preparation to forming cracks that impair flame resistance because a continuous protective densified layer is not formed. The determination of total carbohydrates revealed significant changes at various wood depths after surface charring. These changes were more predictable in radial specimens due to the annual ring orientation, because each layer consisted of a similar earlywood/latewood ratio. Finally, when decay resistance was assessed, weight loss was found to be lower in all specimens than in the references. The results suggest that charring at a particular combination of temperature and time improved the investigated properties of the surface-modified beech.