The advent and early developments of reinforced concrete were related to national patenting. This paper proposes an in-depth study of the logic of reinforced concrete patents at the turn of the 20th century, based on the case of Belgium. Before the First World War, a considerable number of systems were patented by private inventors for commercial purposes. Patents on reinforced concrete constitute today a primary source of information, both for their technical content and for the assessment of the market penetration of the innovative material. The scientific reliability of these patents is variable and ranges from the rational to the unrealistic. Propagation of reinforced concrete occurred following international trends, such as Hennebique or Monier, or by local inventors, mainly building contractors. Reinforced concrete started to be considered as a structural material after the French engineering standard of 1906, adopted by Belgium. Moreover, examining these patents helps to understand the structural specificities of the early phase of reinforced concrete. Therefore, this study enhances the conservation process of such construction.