This article proposes an object knowledge environment to support manufacturing systems layout design, as an alternative to classical functional softwares. It justifies this transition to an object-oriented paradigm by the advantages in openness of the system, as well as increased flexibility and modularity, and higher potential for abstraction and hierarchical structure formation. the implemented environment uses the SMALLTALK-80 language. It supports hierarchical classes of objects such as cell, aisle set, facilities structure, flow, set, relationship set, flow networks, independent objects, evaluators, and optimizers. the layout designer can interact directly with all defined objects through the use of individual model-view-controller triads.