What Is Design Development?

A schematic narrative can say "steel frame and rooftop units." DD has to show the bay size, a plausible member depth, the unit capacity, and the room that holds the unit, with structure and architecture agreeing on the floor-to-floor height. Mechanical, electrical, and plumbing mains are routed far enough to prove the ceiling and the shafts work. Fire protection criteria are stated.

This is also when consultant coordination starts to cost real hours. An architect who finishes DD plans without the structural grid from the engineer does not have a DD set. The phase is interdisciplinary by nature. A single-discipline package labeled DD is a progress print.

Outline specs list systems, performance, and often a basis of design product, without the full three-part section a project manual needs. Estimators use them to stop pricing "mechanical, lump sum." If the outline says variable air volume and the estimate assumed packaged units, the gap is visible now, while the equipment can still change.

Product selections in the outline become the argument later, during submittals. A basis of design named in DD and then silently swapped in CDs creates a specification the estimate never saw. Write the substitution down when it happens.

Construction documents add the coordination, details, schedules, and general conditions that a contractor can bid and a building department can review. DD drawings are dimensioned and serious, and they still omit conditions a CD set must show. Expecting bid-day completeness at DD either inflates the fee or produces a CD set that is only a cleaned-up DD set, which bidders will punish with RFIs.

Owners who call late DD "60% CDs" should say so in the contract and attach a sheet list. The nickname does not change the standard of what a bidder is entitled to. Percent labels and AIA phase names need one crosswalk, written once.

DD approval without an updated estimate is how projects discover the budget problem during CDs, after details are drawn. The estimate at DD is the one that should trigger value engineering. Cuts made here can be drawn once. Cuts made after the project manual is written have to be chased through every section.

The architect should not start full CD production on verbal approval. DD comments that reopen the structural system or the exterior wall are SD decisions arriving late. They belong in a formal change to scope before the CD fee is spent.