From Federated Model to Clean Model: A Clash Review Walkthrough

Picture a coordination meeting where the architectural, structural and MEP models finally sit together in one file. Nothing has been built yet, but the model already shows where a duct will meet a beam. This walkthrough follows that moment from the first model merge to the final sign-off, using the same stages a BIM coordinator works through on a real job.

Step one: gather and align

Every discipline brings its latest model. Architecture and MEP often arrive as Revit files, while structure may come from Tekla. The coordinator merges them into one federated model in a tool such as Autodesk Navisworks. Two checks matter before any test runs. First, all models must share one coordinate system, otherwise every result is meaningless. Second, the team fixes the required level of development, because models built to different levels return conflicts that reflect a modeling gap rather than a design problem.

Step two: look before you test

A quick visual pass through the federated model catches glaring errors. Missing or poorly modeled elements lead to false positives or to clashes that never get reported, so this short inspection saves time later. Teams that need dependable MEP content to coordinate against often rely on MEP BIM modeling services so that pipes, ducts and cable trays enter the federated model already modeled to the agreed standard.

Step three: run the tests

The coordinator picks which models to compare, for example structure against HVAC. Then they set the clash type and the tolerance and run the analysis. The result is a conflict list, often a long one on the first run.

Step four: sort the noise from the real problems

Each item gets reviewed. Non-issues are closed. Genuine clashes are grouped by status, location or system, and then ranked by severity. A main plumbing line hitting a primary beam sits at the top. A single conduit touching a non-load-bearing stud sits near the bottom. The software exports a report with screenshots, element IDs and grid locations so designers can find each item quickly.

Step five: assign and track

Every clash goes to the person who can fix it. A duct against a cable tray, for instance, goes to the mechanical and electrical engineers. Status labels such as in progress and resolved keep the whole team accountable.

Step six: re-run until clean

After the owners edit their native models, the updates are exported again and the same tests are repeated. The loop continues until the model is free of interference.

Which clashes show up

Three families appear in most reviews. Hard clashes are physical intersections, such as a duct through a column. Soft clashes break a clearance zone, such as an air conditioning unit with no room for a technician. Workflow clashes, also called 4D clashes, are scheduling conflicts, such as conduit installation planned in the same area and time as a slab pour.

The full definition, benefits and software comparison are in the article on what is clash detection in BIM, which this walkthrough condenses into a single narrative.