Systems and methods for identifying unbuildable part pairs in product data management (PDM) systems. A method includes receiving a product structure having a plurality of nodes with variant conditions. The method includes building, by the client PDM system, a variant condition forest (VCF) corresponding to the product structure and selecting a pair of nodes in the product structure. The method includes determining, using the VCF, whether the variant conditions of each of the selected nodes are satisfiable both separately and at the same time, and if not, marking the selected pair of nodes as unbuildable. The method includes adding the unbuildable pair of nodes to an unbuildable pairs list. The method includes performing a clearance analysis process on the product structure, without processing unbuildable pairs on the unbuildable pairs list, and storing the results of the clearance analysis process.