Within lean manufacturing applications, its contextualization in construction processes is found as lean construction. This approach aims to reduce non-value-adding activities by optimizing processes to maximize efficiency. Thus, the objective of this research was to propose a procedure for adopting the lean construction methodology to contribute to the optimization of building projects. A mixed-method study was conducted with a cross-sectional, descriptive focus based on the case study: construction of a recreational theme park for terminally ill children. A procedure structured in six steps was designed, allowing the adoption of the lean philosophy in project management and the design of a tool to assess the project team's competencies in integrated management systems. The results enabled the definition, design, and delivery of project assets with the highest possible value generation, where lean methodology principles were applied. Likewise, the integrated project systems, stemming from incorporating lean methodology principles, optimized project productivity in building construction.