Single-story buildings let you spread a program across one plane. Multi-story buildings force a harder question: which functions go on which floors, and how do people move between them?

Stacking diagrams answer that question graphically. They show each floor as a horizontal bar, divided into program zones, so the design team can see at a glance where public functions sit relative to private ones, where mechanical floors interrupt the vertical sequence, and where the structural bay pattern repeats or shifts. A stacking diagram is the vertical equivalent of a bubble diagram. It translates adjacency requirements into a three-dimensional strategy before a single floor plan gets drawn.

Floor plate efficiency determines how much of each floor actually serves the program. The circulation multiplier, which typically ranges from 1.3 for simple offices to 2.0 for courthouses, quantifies the gap between net program area and usable area. GSA targets an 80% usable-to-gross ratio for new federal construction. When that ratio drops, every programmed square foot costs more to build, heat, cool, and maintain.

Phasing adds a time dimension. Some projects deliver the full program at once. Others build in stages, constructing a core and shell first, then fitting out floors as tenants arrive or budgets allow. Phased construction demands structural systems that accommodate future loads, mechanical risers sized for full build-out, and stacking strategies that let early occupants function while construction continues above or below them.

On the ARE, NCARB expects you to reconcile program requirements with building configuration. That means reading a stacking diagram, calculating whether a floor plate delivers enough usable area, and judging how phasing alters system sizing and adjacency relationships.