This paper studies engineering design decision-making. We show that the decision-based design framework, which seeks to find the most profitable design, can be separated into a sequence of subproblems. This separation is similar to decomposition but does not require a second-level coordination. We identify conditions under which this separation yields an exact solution and other conditions under which the error can be bounded. This separation provides a different way to solve the decision-based design framework and indicates a way to apply the principles of decision-based design to design processes.