CAD Data Interoperability with IFC Format: Complete Guide for BIM Professionals

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In an increasingly digitized construction sector, the challenge of CAD data interoperability has become crucial for all stakeholders in the value chain. Multidisciplinary teams must collaborate effectively despite using different software, each saving projects in proprietary native formats (.rvt for Revit, .pln for ArchiCAD, etc.). This technological diversity creates a fundamental need for a standardized, neutral, and reliable exchange format.

The IFC (Industry Foundation Classes) format precisely meets this need by offering a CAD data exchange schema specifically designed for architecture, engineering, and construction (AEC). As an open and interoperable format, IFC facilitates communication between different software applications, allowing architects, engineers, builders, and managers to effectively share 3D model data and associated information throughout the lifecycle of a construction project.

History and Evolution of IFC Format

The development of the IFC format began in 1994, when Autodesk formed an industrial consortium to advise the company on developing a set of C++ classes that could support integrated application development.

This alliance was reconstituted as an industry-led non-profit organization, with the objective of publishing the Industry Foundation Class (IFC) as a neutral AEC product model addressing the building lifecycle. A new name change took place in 2005, and the IFC specification is now developed and maintained by buildingSMART International.

The chronological evolution of IFC versions shows the constant improvement of the format:

  • IFC 1.0 (June 1996): First official version
  • IFC 2.0 (March 1999): Significant improvements to the structure
  • IFC 2x3 (February 2006): Version widely adopted in the industry
  • IFC4 (March 2013): Major extension of capabilities
  • IFC4.3 Add2 (2024): Most recent version integrating advanced functionalities

Global adoption of the format has continued to grow, particularly due to its status as an international standard ISO 16739-1:2024. Several governments, including Denmark, Finland, and Norway, have made the use of IFC mandatory for publicly funded construction projects, thus accelerating its adoption in the industry.

Technical Characteristics of IFC

Fundamental Structure and Data Architecture

The IFC format defines an entity relationship model based on the EXPRESS language, comprising several hundred entities organized in an object-based inheritance hierarchy. These entities cover:

  • Construction elements (IfcWall, IfcFloor, IfcWindow, etc.)
  • Geometric components (IfcExtrudedAreaSolid)
  • Basic structures (IfcCartesianPoint)
  • Technical attributes and properties

IFC is designed to overcome data exchange barriers between different design and project management software. It is based on several fundamental principles:

  • Openness: Format not controlled by a specific vendor
  • Interoperability: Facilitates collaboration between different software applications
  • Extensibility: Allows the addition of new classes and properties as needs evolve
  • Domain neutrality: Covers a wide range of domains in the construction industry

File Formats and Encodings

IFC defines several file formats that can be used, supporting different encodings of the same underlying data:

  • IFC-SPF (.ifc): The most widely used, offering compact size and readable text
  • IFC-XML (.ifcXML): Suited to interoperability with XML tools, but generally 300-400% larger than the standard .ifc format
  • IFC-ZIP (.ifcZIP): Compressed version to reduce file size

Geometric Capabilities and Differences Between Versions

An important technical distinction exists between the main versions of the format:

  • IFC2X3 presents certain limitations in terms of geometric representations. This version does not support B-rep (Boundary Representation) and generally represents objects using polyhedra, sweeps, or basic CSG (Constructive Solid Geometry) shapes.
  • IFC4 removes this limitation by offering support for complete B-rep shapes, significantly improving the geometric fidelity of models. However, the geometric representations provided by IFC2X3 remain sufficient for many applications.

The geometric modeling capabilities of IFC formats are central to CAD interoperability but present certain specificities related to the building-oriented structure of the format.

Applications and Advantages of IFC in the AEC Industry

Data Exchange Between Heterogeneous Software

The main asset of IFC lies in its ability to serve as a neutral exchange format between various BIM applications. This enables:

  • Effective collaboration between teams using different software (Revit, ArchiCAD, etc.)
  • Standardized sharing of building information throughout the project lifecycle
  • Reduction of errors and data loss during conversions between proprietary formats

Multiple Roles in Construction Projects

IFC plays several critical roles in the BIM ecosystem:

  • OEM-supplier collaboration: Facilitates secure exchange of sensitive data between partners
  • CAD migration: Enables transfer of models between different platforms
  • Reusability and validation: Ensures data consistency across different project phases
  • Long-term archiving: Ideal neutral format for long-term preservation of project data

Certification and Compliance

BuildingSMART International has defined a certification process to ensure that the correct IFC data import and export processes are followed. All IFC-certified programs are capable of reading, writing, and exchanging information with other software solutions according to the data provided by buildingSMART.

Specific Application Domains

The IFC format is particularly suited to the following domains:

  • Architecture and building design
  • Structural engineering
  • Building services (MEP - mechanical, electrical, plumbing)
  • Facility management
  • Construction and project planning

CAD Interop Solutions for IFC Interoperability

CAD Interop distributes several software solutions to visualize, convert, compare, and utilize IFC files. Here are the main solutions compatible with the IFC format:

3DViewStation: Advanced Visualization and Analysis of IFC Models

3DViewStation is a powerful BIM & AEC visualization solution for desktop computers, mobile devices, browsers, and virtual reality. It offers:

  • Reading of all major BIM and construction file formats (Revit, IFC, GLTF, CPIXML)
  • Complete support for classic 2D formats (DWG, DXF, DWF, PDF)
  • Analysis features such as measurements, cross-sections, and collision detection
  • Use in VR to "experience" a construction project in real size
  • Uniform user interface for all formats, reducing training costs

This solution represents a considerable advantage compared to using multiple free viewers that often lack advanced features and interface uniformity.

CADfix: Repair and Simplification of IFC Data

CADfix is a cutting-edge software solution for translation, repair, healing, defeaturing, and simplification of CAD models. Particularly useful for IFC data, it offers:

  • Smooth translation of CAD models for improved compatibility with CAD, CAM, and CAE applications
  • Repair of geometric and topological defects in CAD models
  • Advanced geometric processing for preparing CAD models for simulation and manufacturing
  • Minimization of downstream rework of CAD models
  • Seamless integration into PLM tools or workflow automation

SimLab: Creation of Immersive Experiences from IFC Models

SimLab Composer is a visualization and VR creation software developed by SimLab Soft. For IFC models, it allows:

  • Importing, visualizing, rendering, and animating 3D CAD models
  • Sharing and collaborating on BIM projects
  • Automating and improving visualization and simulation workflows
  • Creating virtual reality experiences from construction models
  • Converting between IFC and other formats via CADVRter

Best Practices for IFC Exchanges

Successful implementation of IFC interoperability relies on several essential best practices:

Preliminary Coordination Between Stakeholders

Most projects that encounter difficulties do so due to a lack of preliminary coordination. It is recommended to:

  • Organize a BIM coordination meeting to agree on the following elements:
    • Project location and coordinates
    • Project north direction
    • Floor configuration
  • Prepare a BIM manual and share it with all stakeholders, including:
    • Stakeholders and their exact responsibilities
    • Data exchange protocol
    • Data agreed upon during the BIM coordination meeting
    • Project-specific BIM requirements

Model Optimization for IFC Export

The quality of IFC export greatly depends on model preparation:

  • Verify that the model complexity is appropriate before any IFC work
  • Use reference points (Survey Points) as a common reference point to facilitate coordination of models from different programs
  • Avoid overly complex geometries that can cause errors during translation
  • Clean the model of data that is no longer needed
  • Check all floor heights relative to models from other disciplines

Post-Export Validation of IFC Files

Before distributing models to external parties, it is recommended to:

  • Reopen exported IFC files in the original application to directly compare the model before and after export
  • Open the IFC file in another application to check its compatibility
  • Use free viewers such as Autodesk Viewer to check content and detect potential errors

ArchiCAD-Specific Configuration

For ArchiCAD users, the following tips can improve IFC exchanges:

  • For rooms not delimited by walls, use the line tool and configure it to act as a zone boundary
  • Avoid using floors as space for sketches or temporary storage for alternative design solutions
  • Consider and import levels used by other disciplines
  • Introduce quality control measures using graphic overrides or the interactive schedule

Challenges and Future Perspectives

Despite its many advantages, IFC interoperability still presents certain challenges to overcome:

Current Limitations

  • Transferring generic CAD models with shared parts and sub-assemblies can be difficult due to inherent limitations of the format
  • The IFC structure, optimized for buildings, may require conceptual reorganization when converting non-BIM data
  • Geometric representations vary between versions, with limitations in earlier versions

Promising Developments

The IFC format continues to evolve to meet the growing needs of the industry:

  • New versions such as IFC4.3 introduce significant improvements in geometric representation and exchange capabilities
  • Open-source tools like IfcOpenShell offer advanced features for reading, writing, and modifying all IFC schemas
  • Growing capabilities include:
    • Multithreaded conversion of implicit IFC geometry to explicit polygons
    • Geometric analysis via BVH trees, voxels, and 2D drawing generation
    • Conversion to other formats (OBJ, DAE, GLB/GLTF, STP, IGS, XML, SVG, H5)

IFC interoperability remains a constantly evolving field, with continuous improvements aimed at facilitating data exchange between different stakeholders in the construction industry. The solutions offered by CAD Interop play a crucial role in this evolution by providing powerful tools to visualize, convert, repair, and utilize IFC models in different professional contexts.

By adopting best practices and using appropriate tools, AEC professionals can fully leverage the potential of IFC to improve collaboration, reduce errors, and optimize workflows in their construction projects.

3DViewStation

CADfix

SimLab