This study develops a decision method for the implementation and assessment of standardisation in order to improve the Replacement & Renovation process of hydraulic structures. Possible improvements in the Replacement & Renovation process and the implementation of standardisation were identified by conducting semi-structured interviews. A general decision method results from combining the identified improvement points and the basic design principle. This general decision method is further developed by describing the required steps, decisions, input, and generated output. This decision method is a starting point for asset management organisations that want to start with implementing standardisation into the Replacement & Renovation process. A potential benefit of using the decision method is increased efficiency of the design process, as a learning curve is expected, saving time and money. Furthermore, the results can be used for an in-depth discussion about the feasibility of standardisation in the considered management area.