How to fix clash errors in IFC models exported from Revit
Coordination · 8 min · 2026-08-05
A practical guide to understanding and fixing the most frequent clashes in IFC models exported from Revit: real causes, export settings and coordination workflow.
If you coordinate models in IFC format, this has surely happened to you: you export from Revit, open the model in your coordination tool and hundreds of clashes appear that you did not see in Revit. Before writing off the model, it is worth understanding that many of those interferences are not design errors, but a consequence of how the IFC was exported.
In this guide we review the most frequent causes of clashes in IFC models exported from Revit and how to fix them, from export settings to the coordination workflow.
1. Understand what a "clash" in IFC really is
A clash is the geometric overlap of two elements that should not occupy the same space. In practice there are three types:
- Hard clashes: two solids physically intersect (a pipe crossing a beam).
- Soft clashes / clearance: no intersection, but the required minimum clearance is invaded (for example the maintenance space of a piece of equipment).
- Workflow clashes: sequencing or duplication problems that are not geometric but management-related.
Much of the "false clashes" that appear when exporting from Revit fall into categories you can filter or fix at the source.
2. Check the export geometry (cause #1)
Revit lets you export geometry in different ways, and this directly affects clash detection. In File → Export → IFC → Modify setup, pay attention to:
- Tessellation vs. BREP: tessellation approximates curved surfaces with flat faces. If the level is too coarse, curved pipes and ducts become "faceted" and generate apparent intersections. For coordination, prefer a representation that preserves geometry better.
- "Export only elements visible in view": if your 3D view has sections or filters, you will export an incomplete model and the clashes will not be representative.
- View detail level: exporting from a view set to "Coarse" reduces the geometric detail of many families.
3. Mind the base points and origin coordination
One of the quietest causes of miscoordination is the origin point. If each discipline exports relative to a different origin (Project Base Point vs. Survey Point vs. Internal Origin), the models will not line up when federated and you will see whole offsets interpreted as thousands of clashes.
Agree with the whole team on a single shared-coordinates criterion and check, in the IFC export settings, the coordinate option ("Current shared coordinates" is usually correct in federated projects).
4. Classify elements correctly (correct IfcClass)
If a family is exported with the wrong IFC class (for example a furniture element
mapped as IfcWall), your coordination tool will group it wrong and the
clash rules between disciplines will produce nonsense. Review the category-to-IFC-
class mapping (export mapping file) so each element has its correct
IfcClass. This is also a model-quality requirement, not just a
coordination one.
5. Filter before reporting: not every clash matters
Reporting 5,000 unfiltered clashes is counterproductive. A healthy coordination workflow:
- Define realistic tolerances (for example, ignore intersections of a few millimeters caused by tessellation).
- Group by discipline pairs (ARC vs. STR, STR vs. MEP...) to attack the relevant conflicts first.
- Discard "expected" clashes (elements hosted in one another, such as a recessed light in a ceiling).
- Prioritize by severity and construction impact.
6. Fix at the source and re-export
The clash is resolved in the native model, not in the viewer. Once the design is adjusted in Revit, re-export with the same settings and compare the new version with the previous one to confirm the interferences actually dropped. Keeping version traceability is key to demonstrate the improvement to the client.
Quick checklist before coordinating
- Do all disciplines use the same coordinate origin?
- Was the geometry exported with enough detail (not faceted)?
- Does each element have its correct
IfcClass? - Did you define tolerances and filters before counting clashes?
- Does the exported model include all elements (no view filters)?
Automate your IFC quality control
Many clashes originate from model-quality problems (classification, naming, coordinates) that can be detected before coordinating. With BIMaudit you can audit your IFC model against a public standard aligned with ISO 19650 and detect those gaps in minutes, 100% deterministically and with a traceable report. So you arrive at coordination with a much cleaner model.