Clash detection
Checking combined discipline models for elements that occupy, or encroach on, the same physical space.
Clash detection is the process of comparing the models of different disciplines — architecture, structure, mechanical, electrical, plumbing — once they have been combined into a single coordinated view, to find places where elements conflict. The aim is to catch and resolve those conflicts on screen, during design, instead of discovering them on site, where they are far slower and more expensive to fix.
Conflicts are usually grouped into two kinds. A hard clash is a solid overlap: two objects trying to occupy the same volume, such as a duct running through a beam. A soft clash (or clearance clash) is a violation of a required tolerance or access space, such as a pipe routed too close to a wall to allow for insulation or maintenance. Some workflows also flag workflow or time-based clashes, where two elements coincide at the same point in the construction sequence.
In practice, discipline models are first brought together into a federated model, then checked with rule-based tools that report each conflict as a trackable issue — often exchanged and resolved through an open format so the responsible party can act on it. Clash detection is one of the most tangible benefits of coordinated modelling: it turns coordination from a manual drawing-overlay exercise into a measurable, auditable activity, and it is the core of a BIM Coordinator's day-to-day work.
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