What Is Clash Detection?

Clash detection is the process of finding places where two building elements, usually from different disciplines, occupy the same physical space or otherwise conflict in a way that would prevent the building from being constructed as drawn.

Hard Clashes vs Soft Clashes

A hard clash is a direct physical collision: a duct routed straight through a structural beam, a pipe running into a wall where there's no penetration shown. These are usually unambiguous once found, the elements literally can't occupy the same space.

A soft clash, sometimes called a clearance clash, is different. It's not that two elements physically overlap, but that they're placed too close together to allow for proper access, maintenance, or code-required clearance. A panel that technically fits next to a wall but doesn't leave enough clearance to open it is a soft clash. These require more judgment to catch because nothing is technically overlapping on the drawing.

How Clash Detection Has Traditionally Worked

Before dedicated software, clash detection meant physically overlaying drawings, historically on a light table, later by toggling CAD layers on and off, and looking for places where elements from different disciplines conflicted. BIM software introduced automated clash detection within a single coordinated model, which was a major step forward, but it depends on every discipline actually modeling in that shared environment at a compatible level of detail. A lot of real-world coordination still happens across separate 2D drawing sets that were never modeled together in the first place.

Where Clash Detection Tends to Break Down

Even with BIM tools available, clashes often get caught late, at a coordination meeting, during shop drawing review, or worse, in the field, because the drawings being compared weren't actually aligned and checked systematically earlier in the process. Manual overlay work is slow and easy to get wrong, especially when drawings from different disciplines are at different scales or use different reference points, which makes the alignment step itself a source of error before any clash comparison even starts.

How AI Changes the Process

Structured AI's Overlay feature finds every sheet and detail covering the same area of a building and overlays them automatically, architectural over structural over MEP, aligning views even when they're drawn at different scales. That removes the manual alignment step that used to eat most of the time in a coordination review, and it means the comparison happens on every relevant sheet, not just the ones someone remembered to check.

The same AI agents that run this overlay process also perform the underlying clash checks, and the overlays themselves get surfaced to the team, so what a reviewer sees is the actual evidence the system used, not a separate visualization built afterward.

FAQ

What's the difference between clash detection and coordination review? Clash detection is usually the specific, mechanical process of finding overlaps or clearance issues between elements. Coordination review is broader, encompassing clash detection along with other checks like making sure notes, specs, and drawings across disciplines all agree with each other.

Does clash detection only apply to MEP versus structural? No, though that's a common source of clashes. It applies to any two disciplines whose work occupies the same physical space, which can include architectural finishes conflicting with structural elements, or civil utilities conflicting with foundation work.

Can clash detection be run on 2D drawings, or does it require a 3D model? It can be run on 2D drawings. Structured AI works across .pdf, .dwg, .rvt, and .ifc files, so overlay-based clash detection doesn't require a fully coordinated 3D model to be useful.