Revit Project Management: Interference Check for Clash Detection in CAD Teacher VDCI Video Series.

Welcome to the CAD Teacher VDCI video series for Revit Project Management. In this comprehensive tutorial, we'll explore Interference Check—Revit's built-in clash detection system. While not as robust as dedicated coordination software like Navisworks, Revit's native clash detection provides a valuable first line of defense for identifying conflicts between building systems. Today, we'll demonstrate this by running interference checks between architectural and mechanical models.

Navigate to the Collaborate tab, where you'll find the Interference Check tool positioned on the far right of the ribbon. Click on Interference Check, then select "Run Interference Check." The tool offers limited but focused functionality—you can only run clash detection between your current project and one linked project at a time. This constraint represents one of the tool's primary limitations compared to more sophisticated coordination platforms.

When setting up your clash detection parameters, you'll notice the interface presents categories from both your current project and the selected linked model. For this demonstration, we'll focus our analysis on how architectural walls interact with mechanical systems. Strategic category selection is crucial here—checking too many categories simultaneously can generate an overwhelming number of clashes that become difficult to manage and prioritize effectively.

Let's begin with a targeted approach by selecting only "Walls" from the architectural model, then choosing "Flex Ducts," "Ducts," "Duct Fittings," and "Air Terminals" from the mechanical systems. This focused selection allows us to concentrate on the most critical wall penetrations that typically require fire-rated assemblies, dampers, or other specialized treatments.

Once Revit completes its interference analysis, the results panel displays all detected conflicts organized by category. In this case, we're seeing clashes between walls and air terminals, duct fittings, and ducts, with no conflicts detected in flex ducts—which is expected given their flexible nature and typical installation practices.

The initial results view can appear overwhelming and difficult to interpret without proper context. This is where Revit's visualization tools become essential for meaningful clash analysis. The key to effective clash review lies in your ability to locate and visually inspect each conflict within the 3D model environment.

To examine specific clashes, expand the relevant category—in this case, "Ducts"—and select the first detected conflict. The interface provides detailed information about both conflicting elements, including the linked model details, category classifications, family types, and workset assignments. This metadata proves invaluable for coordination meetings and clash resolution documentation.

For spatial visualization of clashes, use the "Show" function to locate conflicts within your current view. Clicking "Show" cycles through different views where the clash is visible, helping you understand the conflict's context within the overall building design. When you identify a clash location, switch to your 3D view for the most comprehensive understanding of the spatial relationships involved.

Optimizing your 3D view settings significantly improves clash visualization. Change your visual style from "Hidden Line" to "Wireframe" to see through solid elements, though this can create a visually complex display that requires practice to interpret effectively. When selecting clashing elements, walls often provide clearer visual feedback than mechanical components, making them easier starting points for clash investigation.

Advanced visualization techniques can dramatically improve your clash analysis workflow. Use section boxes to isolate specific building areas, allowing you to focus on particular zones without visual distraction. Additionally, consider switching to "Shaded" view mode, which renders elements as solid colors and can make individual components more distinguishable within complex mechanical layouts.

Don't hesitate to modify your view's visibility settings to enhance clash identification. For instance, turning off roof categories in the Visibility/Graphic Overrides dialog can provide clearer sight lines into mechanical systems, making it easier to locate and understand specific conflicts. These temporary view modifications are essential tools for effective coordination workflows.

As you navigate through different clashes, pay attention to recurring patterns—often the same architectural elements are penetrated by multiple mechanical components. This information helps prioritize coordination efforts and identify areas where design modifications might resolve multiple conflicts simultaneously. For example, a duct that's too wide for a wall opening might indicate a need for structural modifications anyway, making it a high-priority coordination item.

Revit's clash detection includes basic reporting functionality through HTML export. However, these reports have significant limitations—they essentially mirror the interface you see within Revit but rely solely on element ID numbers for identification, making them less useful for project stakeholders who aren't intimately familiar with the model structure.

The tool's limitations become more apparent when attempting to run clash detection between two linked models, such as mechanical and structural systems. Since you can only compare your current project against one linked project, running a mechanical-versus-structural clash requires closing your current file, performing a "Save to Central" operation, then opening the structural model to establish it as the current project.

This workflow constraint represents a significant limitation compared to dedicated coordination software, which can simultaneously analyze multiple linked models. For complex projects with extensive coordination requirements, many teams use Revit's interference check for preliminary reviews while relying on Navisworks or similar platforms for comprehensive clash detection and resolution workflows.

Understanding these limitations helps you develop realistic expectations and establish appropriate workflows for your project coordination needs. While Revit's built-in clash detection serves as an excellent starting point for identifying obvious conflicts, professional coordination workflows typically benefit from more sophisticated tools designed specifically for multi-discipline clash detection and resolution.