The bi-layer diaphragm walls are a new type of slurry wall designed to have an improved waterproofness, aimed to be used in situations with risk of water leakages. In this walls, the waterproof system is made of a second concrete layer, which is sprayed while the interior excavation take place. In this way, the second layer has also a structural role, besides the waterproofing one. The research project was structured in four main areas: a) Sectional level analysis; b) Structural level analysis; c) Bond between layers; and d) General design and optimization. The objective of this communication is twofold, on the one hand, the main results reached in the research project (which lead to the doctoral thesis of the first author) are summarized. On the other hand, based on the latest results related to the parametric analysis, design recommendations for the construction of these walls are given. For this purpose, a classification of the construction sequences is proposed, focused on ease the design of this type of walls.