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.

The paper describes a method of structural repair to damaged elements of protected timber houses. Emphasis is laid on minimum intervention in the valuable material that needs to be preserved to the maximum possible extent, especially without larger interventions in the visible parts. The designs will find application in situations where it is not possible or appropriate to use common building methods, and it is necessary to carefully fill out or substitute bio-damaged parts of structural elements. The material for the production of fillings of structural elements corresponds to the originally used wood species; in the case of contact with the ground, oak is the choice due to its durability. Small caverns are filled with earth-based mortar with lime, casein, and chopped wheat straw. Such mortar mixtures were subjected to laboratory tests, which have shown that earth-based mortar (E) and earth mortar with lime putty modification (EL) have very similar physical, mechanical, and hygric properties. The properties significantly changed when curd cheese/casein was added to fresh mortar (ELC): the mechanical strength of hardened mortar increased substantially, and the diffusion of water vapours dropped, which is very beneficial for careful repairs of timber elements. The combination of timber and mortar filling provides a suitable means of repairing locally decayed timber members.

The goal of the work was to evaluate mechanical performance of full-scale timber beams containing scarf joint with a dowel. Work focused on standard testing using modular system to obtain effective stiffness and strength of the beams with and without the joint. The work further researched a contact zone between two timber parts of the joint – at the scarf face. This was carried out using non-destructive optical technique – digital image correlation (DIC) and newly developed algorithm. The joint was made of Norway spruce, dims. 6×0.2×0.24 m and was loaded by two modes: a) 3-point bending and b) 4-point bending. During the loading, a sequence of images was acquired for further investigation of contact zone using the proposed algorithm. The joint with scarf and dowel provided enough effective stiffness, ie. 73–93% for 3-point bending test and 71% for 4-point bending with respect to MOE measured on reference solid beams. Effective strength of the joint was also relatively high and in a range of 55% and 60% with respect to reference solid beams in both 3-point and 4-point bending tests. Contact length differed for loading modes. Mean contact length in symmetrical 4-point bending was about 40%, for asymmetrical 3-point bending test, it was approx. 20% on face closer to support and 44% on a face closer to loads.