Enterprise architecture software design is all about composing applications to assemble value-added solutions rather than standalone products. Yet, each product and technology may have been designed and developed separately because of software engineering practices, management control over the deliverables, or technology acquisitions. To promote efficient assembly, solutions must be architected in a similar style, adhering to fundamental design principles while leveraging capabilities available in modern environments and relevant platforms. Furthermore, business agility and cost requirements dictate the identification of common capabilities and their development as reusable components across products and solutions. The 4x6 Tiered Architecture Method presented in this paper imposes a structured design, in terms of steps to follow, structure and documentation, for the logical view of an enterprise solution. Application of the 4x6 method to the analysis of an enterprise solution yields a six-tiered architecture structure and an abstract architecture specification. This specification expresses the various components, dependencies and design patterns using a graph-based data model (or "architecture catalog") and blueprint, the latter expressed as both a diagram and XML document. The 4x6 Method has been applied in practice; this experience indicates that this method results in higher quality architecture and requires lower effort for both constructing and reviewing the architecture and its documentation.