How to Import CAD into Revit?

Importing or, more commonly, linking CAD files into Revit is a fundamental process for integrating existing design data, such as site plans, floor plans, or detailed drawings, into your Building Information Model. This tutorial will guide you through the recommended method of linking CAD files, which keeps your Revit project file size manageable and allows for easy updates if the original CAD file changes.

Introduction

Integrating CAD drawings into your Revit project can serve various purposes: using existing floor plans as a base for modeling, referencing site information for context, or incorporating specific details that might not be modeled directly in Revit. While the term "import" is often used generically, Revit offers two distinct methods: "Link CAD" and "Import CAD." Linking is generally preferred as it maintains a connection to the original CAD file, allowing for updates, whereas importing embeds the CAD data directly into your Revit project, increasing file size and losing the live link. This tutorial will focus on the more flexible "Link CAD" method.

Prerequisites

• Revit software is installed and running.
• A CAD file (e.g., DWG, DXF, DGN) ready for use.
• (Recommended) Ensure your CAD file is "clean" (purged of unnecessary layers, blocks, and linestyles), drawn to scale, and preferably has its origin (0,0,0) at a logical and known point.

Steps

1. Open Your Revit Project and Target View

1. Launch Revit and open the project where you intend to bring in the CAD file.
2. Navigate to the specific view where you want the CAD file to appear, such as a floor plan, site plan, or drafting view.

2. Access the "Link CAD" Tool

1. Go to the Insert tab on the Revit ribbon.
2. In the Link panel, click on the Link CAD button.

3. Browse for Your CAD File

1. An "Import/Link CAD Formats" dialog box will appear.
2. Navigate to the folder where your CAD file is stored.
3. Select the desired CAD file (e.g., a .dwg file).
4. Do not click "Open" yet. First, adjust the settings at the bottom of the dialog box.

4. Configure Link CAD Settings

Carefully review and adjust the following settings, as they are crucial for how the CAD file will appear and behave in your Revit project:

• Colors:
  • Preserve: Keeps the original colors from the CAD file.
  • Black & White: Converts all CAD colors to black and white lines. This is often preferred for clarity in Revit.
  • Invert: Inverts the colors (useful if your CAD has a black background and you want it on Revit's white background).
• Layers/Levels:
  • All: Imports all layers from the CAD file.
  • Visible: Imports only the layers that were visible in the CAD file's last saved state.
  • Specify: Allows you to choose which specific layers to import after clicking "Open." This is excellent for keeping your Revit model clean.
• Import Units:
  • Auto-Detect: Revit attempts to determine the units from the CAD file.
  • Custom Units (e.g., Millimeters, Meters, Inches, Feet): Manually select the units. This is critical for correct scaling. Always verify or manually set this to match the units the CAD file was drawn in. If your CAD was drawn in meters, select "Meters." Incorrect units will result in an incorrectly scaled CAD link.
• Positioning: This determines where the CAD file will be placed in your Revit project.
  • Auto - Center to Center: Revit centers the CAD file's extents to the center of your current Revit view. Good for quick, rough placement.
  • Auto - Origin to Origin: Aligns the CAD file's World Coordinate System (WCS) origin (0,0,0) with the Revit project's internal origin. Ideal if your CAD file is precisely located relative to a known origin.
  • Manual - Center: Allows you to manually place the CAD file by clicking its center point in your Revit view after clicking "Open."
  • Manual - Origin: Allows you to manually place the CAD file by clicking its origin point in your Revit view after clicking "Open."
• Place at:
  • Current View: Places the CAD file only in the active view.
  • Select Level: Places the CAD file on a specific level, making it visible in all views associated with that level. This is generally preferred for floor plans and site plans.
• Orient to View: If checked, the CAD file will rotate to align with the current view's orientation.

5. Execute the Link

1. After configuring all desired settings, click Open.
2. If you selected a "Manual" positioning option, you will need to click in your Revit view to place the CAD file. Otherwise, it will appear automatically based on your "Auto" positioning setting.
3. The CAD file will now appear in your Revit project.

6. Pin and Adjust (Optional)

1. The linked CAD file will typically be pinned by default to prevent accidental movement.
2. To move, rotate, or scale the CAD link, select it, then click the "Unpin" icon (or type UP) on the Modify panel.
3. Use the "Move" (MV) or "Rotate" (RO) tools to precisely position the CAD file.
4. Once the CAD file is correctly positioned, it is good practice to re-pin it to lock its position and prevent accidental changes.

7. Manage Linked CAD Files

1. To manage all linked CAD files in your project, go to the Insert tab > Manage Links button.
2. In the "Manage Links" dialog box, navigate to the CAD Formats tab.
3. Here you can:
   • Reload: Update the CAD link if the original file has been modified.
   • Unload: Temporarily hide the CAD link from all views without removing it from the project.
   • Remove: Permanently remove the CAD link from the Revit project.
   • Change Path: Update the file path if the original CAD file has been moved.

Conclusion:

Linking CAD files into Revit is a powerful way to leverage existing data and enhance your BIM workflow. By understanding the various settings, particularly "Import Units" and "Positioning," you can ensure your CAD data integrates seamlessly and accurately into your Revit project. Remember that linking is generally preferred over importing for better project performance and easier management of external data.