Circular materials management is a key concept towards Sustainable Development. In this fashion, Transformable Design contributes to the reduction of excessive waste generated by maintenance and demolition, through the reuse of building elements and materials. Nevertheless, current building practices will only shift towards Transformable Design provided expected (mid or long term) environmental benefits and financial viability. This research aims to promote the practical implementation of dynamic design and to develop a usable assessment method considering the lifelong impacts of Transformable Design. In order to guaranty its objectivity, universality and user-friendliness, the method is implemented into a practical assessment tool compatible with Building Information Modelling (BIM). First, we define the kind of feedback provided by the tool and the way it is communicated to specific users. Then we create a method to assess the capacity to respond (and be adapted instead of demolished) to transformation and maintenance needs. On one hand, we define the factors impacting on the need for maintenance; on another, the factors defining the Transformation Capacity of a design. Then the implementation in a BIM tool, through the use of Dynamo and Autodesk Revit, allows to check the validity of the assessment on different case studies and the relevance of the feedback provided. The designer compares different maintenance and design scenarios to make better-informed design decisions.