Spatial construction—creating or copying spatial arrangements—is a hallmark of human spatial cognition. Spatial construction appears early in development, predicts later spatial and mathematical skills, and is used throughout life. Despite its importance, we know little about the cognitive processes underlying skilled construction. Construction tasks are highly complex but analyses have tended to focus on broad-stroke measures of end-goal accuracy. In this paper we introduce a novel behavioral coding formalism to characterize an individual’s entire construction process, examine many individuals’ processes in aggregate, and summarize patterns that emerge. The results show high consistency at certain points occurring throughout the construction, but also indicate flexibility in the interim paths that lead to and diverge from these points. Our approach offers a new method that can more precisely describe the behavioral patterns observed during construction in order to reveal the underlying cognitive processes engaged, and capture individual differences in building expertise.