In CSI’s project delivery / design-phase framework, the design development (DD) phase is where the emphasis shifts from big-picture concepts to more detailed, technical decisions:
Earlier phases like schematic design focus on overall relationships, general size, massing, and functions of spaces and systems.
Once the project enters design development, the team refines those schematic decisions into more precise technical solutions, coordinating architectural, structural, mechanical, electrical, and other systems, and beginning to define materials, systems, and outline specifications.
By the construction documents phase, the design is largely established and the emphasis is on fully detailing and documenting the agreed technical decisions for pricing, permitting, and construction.
CSI’s practice guides describe DD as the phase in which design decisions are “developed and refined” and more technical information is incorporated, bridging from conceptual/schematic level to the level needed to create final construction documents. That wording corresponds directly to “the emphasis shifts from overall relationships and functions to more technical issues,” which is why Design development (C) is correct.
A. Preliminary design – Not a standard CSI primary phase label; in many frameworks this term is used informally or overlaps with early conceptual planning, where the focus is still on overall functional relationships, not detailed technical issues.
B. Schematic design – Focuses on general arrangement, shape, and relationships of spaces and systems, not yet at the more detailed technical decision level.
D. Construction documents – This phase emphasizes complete, coordinated, enforceable documentation (finalizing drawings and specs), not the initial shift from conceptual to technical; that shift has already occurred in design development.
CSI-aligned references (no external links):
CSI Project Delivery Practice Guide – chapters on Schematic Design, Design Development, and Construction Documents phases.
CSI Construction Specifications Practice Guide – overview of how design phases relate to the development of specifications.
CSI CDT Exam Study/Practice materials – sections describing the purpose and focus of each design phase.
