||Follow up charts require a list of activities, inter-dependencies between activities, and the duration of each activity as its input. This is also true to construction processes where follow up charts for complex projects can cover thousands of construction activities. The management of such a huge list requires a structure. For this purpose, project specific work breakdown structures are developed. Software tools are used in practice for the development of follow up charts, but these tools only document lists of activities and their structure. The structure of the activities is specified by a project manager. A project manager is responsible for the specification of summary tasks and the as-signment of activities to summary tasks. Of course, experts know that for instance a summary task named “structural work” should not include painting activities. However, there exists no formalism that prohibits such an assignment. As a consequence, an extensive manual checking of follow up charts is required. This checking includes the verification of the list of activities concerning completeness and correctness, the verification of summary tasks concerning their struc-ture and their assignments of activities, the verification of the inter-dependencies between activities and the verification of each activity duration. This paper is focused on a formalism to guarantee the correctness of the assignment of con-struction activities to summary tasks including a consistent structure of summary tasks, which is, from a mathematical point of view, the correctness of a structure in the set of construction activities. A mathematical formulation is pre-sented based on set theory and relational algebra. This formulation is applied to construction activities. A prototype has been implemented, and an example is presented where a revitalisation project has been modelled based on the ap-proach that is presented in this paper.