BIM Clash Detection: How to Prevent Costly Construction Errors

Clash detection, the process of finding geometric conflicts between different building systems in a federated BIM model, is often the first VDC workflow a project adopts. It is also the most frequently done wrong.

What Is a Clash?

In Navisworks or Revizto, a "clash" is any intersection or unacceptable proximity between two objects in the model. A structural beam running through a duct is a hard clash. A conduit running into the insulation of a pipe by 1/4" is a soft clash.

The 5-Step Clash Review Process

1. 1Federation All discipline models (structural, mechanical, electrical, plumbing, fire protection) are linked into a single federated model in Navisworks.
2. 2Clash Tests Discipline pairs are tested against each other. Running all disciplines against all others creates noise be selective. Focus on structural vs. MEP first, then MEP vs. MEP.
3. 3Grouping and Triage Clashes are grouped by location, trade, or issue type. Duplicates are merged. Irrelevant clashes (pipes clashing with walls) are filtered out.
4. 4Assignment Each clash group is assigned to the responsible trade with a clear question: who owns this, and who moves?
5. 5Resolution and Re-test Trades update their models, new models are loaded, the clash test reruns. The goal is not zero clashes it is zero unresolved clashes.

"A clash report is a communication tool, not an outcome. The outcome is a coordinated, buildable model."

Common Clash Detection Mistakes

Other common failures:

• No status tracking (new / in progress / resolved / not an issue) without it, the same clashes get re-discussed in every meeting
• No assigned owner every clash needs a trade responsible for resolution
• Treating clash count as a success metric a lower clash count means better modeling, not better coordination

LOD Requirements for Coordination

The models must be at the right level before clash detection produces meaningful results:

• LOD 200: Good for early spatial planning. Too approximate for coordination.
• LOD 300: The minimum for coordination-level clash detection. All major systems with accurate size, elevation, and routing.
• LOD 350: Includes hangers, supports, and sleeves. Required for prefabrication coordination.

The EZ-VDC Approach

Our clash management workflow is built around the principle that every coordination meeting moves issues forward not just identifies them. We use EZ Clash Manager, our own Navisworks plug-in, to streamline clash assignment, status tracking, and coordination report generation, cutting meeting prep time significantly and keeping all stakeholders aligned.

On our projects , we run weekly coordination cycles: model deadline Monday, clash detection Tuesday, meeting Thursday, updated models by Friday. That cadence keeps every trade accountable and prevents coordination from falling behind the construction schedule.