This paper addresses assembly issues in life-cycle engineering design. It outlines a method that supports the designer in making assembly considerations. The basic idea is to incorporate commonly accepted Design For Assembly (DFA) rules into the axiomatic design theory. In our approach, we represent these DFA rules as constraints and functional requirements on the design, along with suggestions on suitable physical solutions, at different levels in the functional and physical hierarchies. An example illustrating use of the method is provided. The validity and usefulness of this approach have been successfully tested in cooperation with two Swedish companies.