The first formal stage of the design phase after the conceptual design period, where initial design concepts are re-evaluated and many early-stage design documents are produced such as early iterations of site plans, floor plans, sections, and elevations. This phase is used to verify the project is feasible, buildable, and conforms to the owner’s and design team’s vision.

Typical items studied during this phase are further function and form analysis, structural feasibility, MEP space layouts, vertical transportation, ingress, egress, generic exterior aesthetics , and floor layouts.