Five clash detection mistakes we see on every second project

Clash detection is meant to catch problems before they reach site. Done badly, it generates a 9,000-line report no-one will ever read and a coordination team that ends up resenting the BIM process. After running over 200 federation workflows since 2021, here are the five mistakes we see most often.

First: not setting a clash tolerance. Hard clashes at 0mm tolerance flag every brick to mortar interface as a critical issue. Set a sensible tolerance per discipline pair (we usually run structure-vs-MEP at 25mm).

Second: skipping the soft-clash pass. Hard clashes catch geometry that overlaps. Soft clashes catch the maintenance access zone around a valve that nobody can reach. Without the soft clash pass, you're building a building that can't be operated.

Third: federating too late. If you wait until stage 4, the design teams have already committed to decisions that are expensive to undo. Run the first federation at the end of stage 3 — even with incomplete models — to surface coordination issues while changes are still cheap.

Fourth: ignoring level differences. A clash filtered by 'same level' will miss the chilled water pipe penetrating the slab into the floor below. Always run cross-level clash sweeps as a final check.

Fifth: treating the report as the deliverable. The deliverable is a coordinated design. The clash report is the diagnostic that gets you there. Move resolved clashes through 'reviewed → assigned → resolved → approved' in BIM Track or Solibri so the team can prove the model is genuinely coordinated, not just analysed.