Linked Models, Coordination, and Clash Detection Basics

Linked Models and the BIM Coordination Workflow

In real projects, a building is never designed by one person or one discipline. The architect models walls, floors, and roofs; the structural engineer models columns and beams; the MEP (mechanical, electrical, and plumbing) engineer models ductwork, piping, and conduit. Revit's linked model system lets each discipline work in its own file while still seeing—and coordinating with—every other discipline. This lesson focuses on linking an MEP model into your architectural host model and using Revit's built-in Interference Check tool to find clashes before they become expensive field problems.

What Is a Revit Link?

A Revit Link (RVT) is a live reference to an external Revit file. Unlike importing geometry, a link stays connected to its source file. When the MEP engineer updates their model, you reload the link and your coordination view updates automatically. The link does not merge the two files; it overlays them, which keeps file ownership and edit permissions clean.

To insert a link, go to Insert tab → Link Revit. In the dialog you choose a positioning method. For this lab you will use Auto – Origin to Origin, which aligns the shared origin point of both files. This is the standard method when both teams have agreed on a common project base point and survey point at the start of the project. If the model appears offset or rotated after linking, that is a sign the origins were not coordinated upstream—a common real-world problem worth flagging immediately.

After inserting, use Temporary Hide/Isolate (the sunglasses icon on the View Control Bar) to isolate levels or categories and confirm the MEP ductwork sits inside the correct floor-to-floor zone. If a duct appears in the wrong story, recheck the origin alignment before proceeding.

Managing Linked Model Visibility

Linked files appear in the Visibility/Graphic Overrides dialog under the Revit Links tab. You can expand each linked file and control visibility by category—for example, turning off architectural walls in the linked model to reduce visual clutter while still showing MEP ductwork. This does not affect the source file; it only controls what you see in your view.

What Is a Clash, and Why Does It Matter?

A clash (also called an interference) occurs when two elements physically occupy the same space in the model. The most common clash in construction is a structural beam running through a duct run. In the field, fixing this conflict may require re-routing duct, lowering a beam, or raising a ceiling—all of which cost time and money. Catching clashes in the model before fabrication or construction begins is one of BIM's highest-value contributions.

There are two types of clashes you will encounter:

• Hard clash: Two solid objects occupy the same space (beam through duct).
• Clearance/soft clash: Elements are within a defined buffer distance of each other (e.g., a duct so close to a beam that a hanger cannot fit).

Revit's Interference Check tool detects hard clashes between selected categories.

Running the Interference Check

Navigate to Collaborate tab → Coordinate panel → Interference Check → Run Interference Check. In the dialog, set the left column to Structural Framing (from your host model) and the right column to Ductwork (from the linked MEP model—select the linked file from the drop-down). Click OK.

Revit returns the Interference Check Report dialog listing every clash as a row. Each row shows the element category, the element ID, and the intersecting element ID. Clicking a row zooms the active view to the clash location. Review each clash carefully—some may be minor overlaps at model boundaries that a structural engineer would accept; others will be significant conflicts requiring redesign.

Exporting the Report and Documenting Clashes

Click Export in the Interference Check Report dialog to save an HTML file. Open it in a browser to confirm it lists each clash with element IDs, categories, and the date/time the check was run. You will convert this to PDF (or print to PDF) and then annotate it with a PDF markup tool.

For each of the three clashes you document:

1. Record both element IDs.

2. Note the categories involved and the floor level.

3. Describe where in the building the conflict occurs (e.g., "Third-floor corridor, grid line C-4").

4. For at least one clash, propose a resolution—such as lowering the duct run by a specified amount, re-routing around the beam, or requesting a structural review to use a shallower beam profile.

Your written description should be clear enough that someone not looking at the model can understand the problem and the proposed fix.

Safety and Professional Practices

Coordination work is performed entirely on CAD workstations. Standard workstation safety applies: adjust monitor height and chair so your eyes are level with the top third of the screen, take short breaks to prevent eye strain and repetitive-strain injury, and keep liquids away from keyboards. When working with large linked models, Revit can consume significant RAM; do not force-quit the application without saving, as this can corrupt the central file in a workshared environment. Always work on a local copy or a detached copy when the exercise file is not a workshared project, so you do not overwrite the class master file.