Straw is a natural material, which is a by-product of cereal production in agriculture. It was often used in civil engineering, mainly as roof tile and also for the production of plaster or as insulation material. Nowadays the traditional ways of building are again gaining popularity and so the demand for straw has increased. In the same way as biotic and abiotic factors affect similar lignocellulosic materials, they also affect straw. These factors bring about various damages. In recent times, it is reported that thatched roofs are at stake when it comes to life expectancy, so solutions need to be found in order to provide their protection. One of the possible solutions is thermal modification, which is the subject of research in this article. Straw was thermally modified in vacuum at five temperatures between 170 °C and 210 °C. From the modified straw we prepared smaller wisps of straw and exposed them to three different sorts of wood-decay fungi according toa somewhat modified standard SIST EN 113. In parallel we also determined the sorption properties of the modified straw. We came to a conclusion that the thermal modification has a similar effect on straw as it has on wood. The higher the final temperature, the less intensive fungal colonisation. The similar effect was observed with sorption properties. Samples modified at higher temperatures were less moist at the same climatic conditions than the control unmodified specimens. While preparing the wisps of straw, some challenges with modified straw occurred. With the rising of the final temperature, the mechanical features of straw deteriorated, meaning that the straw was evermore brittle.
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