LIBRARY // REVIT AND BIM

IFC and OpenBIM: Sharing Models Between Platforms

Not everyone on a project uses the same software. IFC is how their models can still talk to each other.

Not everyone on a project uses the same software. Architects might use Revit or Archicad, structural engineers Tekla, and contractors Navisworks or Solibri. Industry Foundation Classes, or IFC, is the open format that lets these tools exchange BIM information.

What IFC is

IFC is an open data schema for building information, developed by buildingSMART International and published as ISO 16739. It describes building elements, their properties and relationships in a vendor-neutral way.

What openBIM means

OpenBIM is buildingSMART's term for collaborative working using open standards, such as IFC for models, BCF for issue communication and the buildingSMART Data Dictionary for definitions. The idea is that teams can collaborate regardless of software.

IFC versions

IFC has several versions in use, such as IFC2x3 and IFC4, with newer versions extending support for infrastructure. Agree which version and model view definition the project uses, as support varies between tools.

Exporting from Revit

Revit includes an IFC exporter, maintained as an open-source project. Key settings include:

• IFC version and model view definition
• Which elements and views are exported
• Property sets, including Revit and custom properties
• Coordinates and site placement
• Mapping of Revit categories to IFC classes

Save export settings so exports are consistent each time.

Mapping categories

Elements must map to the right IFC classes, such as IfcWall, IfcDoor or IfcSpace. Incorrect mapping, such as generic models exported as IfcBuildingElementProxy, makes models harder to use. Revit lets you set mappings by category and override them per element.

Coordinates

Checking IFC files

Open exported IFC files in a viewer before sharing. Check that elements, properties and locations are correct. Free viewers are widely available.

Common problems

• Missing or incorrect properties
• Proxies instead of proper classes
• Misaligned models
• Large file sizes from overly detailed geometry

BCF for issues

BCF files carry issue information, such as viewpoints and comments, between tools. They're useful for coordination when teams use different software.

When to use IFC

IFC is often required by clients for open deliverables, archives or handover. It's also used for coordination between teams on different platforms.

Agree an exchange protocol

Document IFC settings, versions and checks in the BIM execution plan, so every export follows the same rules and recipients know what to expect.

1. 01What IFC is
2. 02What openBIM means
3. 03IFC versions
4. 04Exporting from Revit
5. 05Mapping categories
6. 06Coordinates

Test exchanges early

Run a test exchange with each partner at the start of the project. Export a small sample, have them import it and report what's missing or wrong. Fixing settings at this point is far easier than discovering problems at a coordination milestone.

IFC isn't perfect, but it's improving steadily. With agreed settings and regular checks, it provides a reliable way to share information across platforms.

If your team needs extra production capacity for work like this, take a look at our Architectural production services, or tell us about your project.