MEP clash resolution in Revit: the complete workflow

The workflow, step by step

1. Detect clashes and export the report. Run your clash tests in Navisworks or any tool that writes BCF, with sensible tolerances, and export the results as Navisworks XML or BCF.
2. Bring the report into Revit. Match each clash to its two elements in the host model or a link. Merge duplicates, set aside clashes already approved or resolved in the report, and group what is left by the run that causes it: one fix often clears several clashes.
3. Split the list by trade. Separate the clashes your trade can fix from those that need another trade or a coordination meeting. Never edit another trade's elements or a linked model to clear your clash.
4. Decide who gives way. Move the service whose change costs least: gravity drainage keeps its fall, structure is never the fix, and a small pipe usually bends around a large duct rather than the other way round.
5. Choose the fix. Pick the simplest change that clears the obstacle and respects the rules of the project: height zones, the ceiling line, clearances, walls that may or may not be crossed, and the fewest added fittings.
6. Apply it and verify it. Split the run, offset or reroute the segment, add the fittings and reconnect. Then re-test: the clash must be gone, no new clash may appear, and what the change affects (airflow, hydraulics, falls, fire ratings) goes to the engineer who owns it.
7. Keep or reject, then re-test the rest. Commit the change as one undo step or roll it back. Re-test the remaining clashes, since a kept fix can clear others, and send what you could not fix to its owner with the reason.

Who gives way: the cheaper change

Coordinators decide most clashes with knowledge that has nothing to do with geometry. Moving a large supply duct adds fittings that change its airflow and pressure drop; bending a small domestic water pipe costs two elbows. A sprinkler main is hydraulically calculated. A condensate line needs its fall. A drain's slope sets its height at every point.

So the question is not "which category ranks higher" but "which change is cheaper, all things considered": the system, its size, its insulation and what an engineer would have to re-check. A large insulated chilled-water main can outweigh a small duct; one duct crossed by many small pipes may be cheaper to move once than every pipe.

Read more in duct vs pipe clashes and gravity drainage clashes.

The rules a fix must respect

• Structure is never the fix. A beam, column or structural wall is an obstacle. If nothing clears, a beam opening is a question for the structural engineer (pipe vs beam).
• The ceiling line and clearances. A drop that breaks the ceiling void, or a route closer than the project's clearance (insulation included), is not a fix.
• Height zones. Each trade has its zone; a sideways move inside it usually beats leaving it.
• Walls. A new crossing of a non-structural wall is a last resort and needs an opening, and a fire-rated wall a damper or firestop; structural walls are hard limits.
• Falls. Gravity drainage never moves up or down; lines that need a fall stay level when they move.
• Slabs. A riser moves only within its storey, never through a new floor opening (riser clashes).
• Fittings. Every added elbow costs pressure, money and installation time; the fix with fewer is usually better.

Resolve Navisworks clashes and BCF issues in Revit

Navisworks finds clashes; it cannot fix them, because the model lives in Revit. The usual round trip is to export the clash report, find each clash again in Revit, make the change by hand and re-run the test. A BCF clash in Revit has the same problem: the issue names the elements, but someone still has to locate them, judge them and edit the run.

ClashFree imports Navisworks XML clash reports and BCF files directly into a pane beside your Revit model (several files merge into one list), matches every clash to its elements in the host and its loaded links, and groups the clashes by root cause so the first group is the one to fix first. You can also pick two clashing elements in Revit without a report.

Automatic clash resolution in Revit: what to automate, what not

Searches for "automatic clash resolution in Revit" usually mean: stop doing the same ten small jobs for every clash. That routine is worth automating: locating the clash, measuring the space around it, splitting the run, offsetting it, placing fittings, reconnecting, re-testing.

The decision is not. Which service gives way, whether a wall may be crossed, whether a duct's extra elbows are acceptable: those depend on the project and its engineers. ClashFree is not fully automatic, on purpose. It does the routine and proposes the fix with its reasoning; you keep it, reject it, or ask for something else in plain words.