Although earth block construction (EB) is supported by numerous scientific works, there is a lack of confidence in its constructive viability, aggravated by the lack of specific technical training. In view of this uncertainty, which is widespread in Spain, it is necessary to provide well-founded technical responses. This article, considering these aspects, presents the design and validation of a tool to assess the constructive viability of EB. For this purpose, 29 case studies are chosen in Spain, which establish the constructive use determinations and indicators to assess a degree of technical suitability. This parameter, as a result of the proposed tool, acts as a support for decision-making, the improvement of the design and, the efficiency of the solutions that use EB. It concludes by validating the tool, demonstrating its reliability and adaptability to any situation. Finally, the case analysis shows how the quality of the product combined with adverse external conditions, even with correct construction designs, defines a common situation where the degree of suitability of the solution is reduced. Therefore, it is also necessary to demand products with guarantees and prescriptions that ensure and offer sufficient technical safety.