The number of applications with thin flat, curved or double-curved elements often produced as architectural elements for façades is rising fast. If the repetition factor of the elements is limited, which is often the case in free-form architecture, the high number of unique moulds makes this type of architecture economically less viable. Furthermore, a large volume of waste is produced through milling as a consequence of the production of unique elements. The reinforcement of thin panels poses specific demands on the material selection and production process, which directly affects their structural performance. This paper discusses a flexible mould technique, which has been developed in order to produce thin double-curved elements with concrete. Fibres are added to provide strength and ductility, the degree to what was determined by flexural testing of prisms and point-loading of thin plates.