Feasibility
A short, inexpensive stage that answers one question: can the site do what you want it to do? Constraints, servicing and indicative civil cost are identified before significant fees are committed.
Concept and detailed design
Concept design produces the strategy that goes to planning. Detailed design produces the documents that get built. Compressing the two together is a common cause of rework.
Construction phase
Site inspections, RFI responses and work-as-executed review close out the design. Budget for this stage — it is where the compliance record is actually created.