According to European regulations, the construction industry supports and strives to save non-renewable natural resources, increases the share of reusable resources in production and attempts to use renewable natural resources as much as possible by creating alternative building materials, such as bio-composites. Various building materials containing hemp shives (HS) are relatively popular and are often used in practice. The properties of these materials vary widely due to the usage of significantly different binders and because the parameters of the HS can significantly affect the properties of the bio-composite. Potato starch (PS), the properties of which have not been studied extensively in the past, was used as a binder in this study. Depending on the type of manufacturing process and technology employed for hemp fibre production, the HS particle shape and size can vary widely, which leads to the following statement: the properties of bio-composites produced by using the same method, but with different HS, may differ significantly. In order to investigate the effects of HS on the properties of bio-composites, including the hydro-thermal properties, an in-depth study was conducted to examine the structure, the physical properties and the particle size of HS. It was discovered that in order to obtain a material of higher compressive strength, the HS with smaller dimensions should be used; however, if enhanced thermal properties are required, the HS with longer particles should be used.