Schedulers consider a variety of constraints when they analyze a project to schedule the construction work for it. Often they will start from some schedule that they recall from a previous project and modify it to meet the new project's constraints. In doing so, they may add, delete, or change activities and links in their working schedule. The knowledge pertaining to identifying constraints and to reapplying them is reusable planning and can be stored with the project data as cases. Besides articulating scheduling constraints to be captured in cases, this paper presents a case-based planner for construction, named CasePlan. CasePlan accumulates planning knowledge based on the causal relationship established by schedulers between constraints, project descriptions, and construction alternatives used for the project. CasePlan stores this planning knowledge as cases, and uses those cases to plan new projects. The implementation of CasePlan is under way.