Design Development (DD)
The phase that develops an approved concept into a defined, coordinated design.
Quick Answer
Design development is the architectural phase that follows schematic design. The team refines the approved concept by choosing materials, defining structural and mechanical systems, and dimensioning plans. The result is a coordinated design detailed enough to price more accurately and to be turned into construction documents without major changes to scope.
The Full Picture
Design development, or DD, takes the approved schematic scheme and answers the questions SD left open. What is the structural system and column grid? How will the building be heated and cooled? What does the exterior wall actually consist of? By the end of DD, the major building systems and materials are chosen and the plans are dimensioned and coordinated between disciplines.
The drawings grow noticeably. Floor plans become dimensioned, sections and wall types are developed, an outline specification lists materials and performance, and engineers provide sized systems and preliminary layouts. Code analysis is also firmed up, since life safety, accessibility, and energy decisions are much harder to change after documentation begins.
DD is where design and construction knowledge need to meet. Contractors involved at this stage review the design for constructability, flag long-lead items, and update the estimate as quantities become more measurable. Estimates at DD are more reliable than at schematic design, but still include design contingency for details not yet drawn.
A common practice is to treat the end of DD as a design freeze for scope-defining decisions. Changes after that point flow through the entire construction document set and often trigger re-pricing. Owners who approve DD with unresolved decisions typically see those decisions return later as redesign, change orders, or value engineering exercises.
Real Examples
Common Misconceptions
People assume: Design development is just schematic design with more drawings.
Actually: DD is where decisions are made about structure, systems, and materials. The added drawings reflect those decisions, not just extra detail on the same concept.
People assume: A DD set is complete enough to construct from.
Actually: DD drawings still leave out many details, coordination, and full specifications. Construction documents are needed to permit, bid, and build the work.
Frequently Asked Questions
What happens during design development?
The team selects structural, mechanical, electrical, and envelope systems, chooses major materials, dimensions the plans, develops an outline specification, and coordinates the disciplines so the design is ready for documentation.
How does design development differ from construction documents?
DD defines what the building is made of and how its systems work. Construction documents add the detailed drawings and full specifications that contractors use to price, permit, and build.
Why do owners approve design development?
Approval confirms the scope, systems, and materials before the expensive documentation phase begins, so later changes are limited to refinements instead of redesign.
Is design development included in the owner-architect agreement?
Standard architect agreements typically list it as a basic service phase alongside schematic design and construction documents, though the scope is set by the contract.
When should a contractor review a DD set?
Ideally before it is finalized. A constructability and cost review at DD lets the team adjust systems and details while changes remain inexpensive.