IFC File Format: A Complete Guide for BIM Teams

What Is IFC?

IFC (Industry Foundation Classes) is an open, vendor-neutral data format for describing building and construction data. Developed and maintained by buildingSMART International, IFC provides a standardized way to exchange BIM models between different software applications without relying on proprietary formats.

In practical terms, IFC is what allows an architect working in Revit to share a building model with a structural engineer using Tekla Structures, or with a contractor using a different platform entirely. The model geometry, spatial structure, material properties, and classification data transfer through the IFC file.

IFC is not just a geometry format. Unlike formats like OBJ or STL that carry only shapes, IFC encodes the semantics of building elements: a wall knows it is a wall, a door knows its fire rating, and a duct carries its flow capacity. This semantic richness is what makes IFC valuable for BIM workflows beyond simple visualization.

IFC Schema Structure

An IFC file follows a hierarchical structure that mirrors how buildings are organized in the real world.

Spatial Hierarchy

The core spatial structure follows this nesting:

• IfcProject — The top-level container. Every IFC file has exactly one IfcProject that defines the project context, units of measurement, and coordinate reference.
• IfcSite — Represents the physical site. Contains geographic coordinates and site-level geometry.
• IfcBuilding — A single building on the site. A project can have multiple buildings.
• IfcBuildingStorey — A floor level within a building. Elements are assigned to storeys to organize the model vertically.
• IfcSpace — An enclosed area within a storey (rooms, zones). Optional but important for energy analysis and facility management.

Building Elements

Within the spatial hierarchy, actual building components are represented by specialized entity types:

• IfcWall, IfcWallStandardCase — Walls with thickness, material layers, and opening relationships
• IfcSlab — Floor slabs, roof slabs, and landing slabs
• IfcColumn, IfcBeam — Structural framing elements
• IfcDoor, IfcWindow — Openings with hardware sets and performance properties
• IfcMember — Generic structural members (braces, struts, ties)
• IfcPlate — Planar structural elements
• IfcStair, IfcRamp — Vertical circulation elements
• IfcDistributionElement — MEP components (pipes, ducts, cables, equipment)

Each element carries geometry (how it looks), properties (what it is), and relationships (how it connects to other elements).

Property Sets

IFC elements carry properties through property sets (Psets). These are named collections of property-value pairs. Some property sets are standardized by buildingSMART:

• Pset_WallCommon — Fire rating, thermal transmittance, load-bearing status
• Pset_DoorCommon — Fire rating, acoustic rating, security rating
• Pset_SpaceCommon — Area, height, occupancy

Organizations can define custom property sets for project-specific data — material codes, cost centers, maintenance schedules, or classification codes specific to their standards.

IFC Versions

IFC2x3 (2006)

The most widely supported version. Virtually every BIM application that claims IFC support can read and write IFC2x3. If you need maximum compatibility across different software and project partners, IFC2x3 is the safe choice.

Limitations: Limited MEP support, no built-in support for alignment (infrastructure) elements, and some geometric representations are ambiguous across implementations.

IFC4 (2013)

A significant update that improved geometric accuracy, added better support for MEP systems, and introduced new entity types for infrastructure (bridges, roads). IFC4 also improved property set definitions and added support for tessellated geometry.

Adoption has been steady but uneven. Most major BIM tools now support IFC4 export, but some downstream tools (viewers, analysis software) may still expect IFC2x3.

IFC4.3 (2023)

The latest major release, with extensive additions for infrastructure projects — railways, roads, ports, and waterways. IFC4.3 also includes improvements to earthworks, alignment geometry, and linear referencing.

IFC4.3 is the future direction for infrastructure BIM, but software support is still catching up. For building projects, IFC4 or IFC2x3 remain the practical choices.

Exporting IFC from Common BIM Tools

From Revit

Revit's IFC export is accessible via File > Export > IFC. Key settings to configure:

• IFC Version: Choose IFC2x3 for maximum compatibility or IFC4 for richer data.
• Export Scope: Export the entire model, specific views, or selected elements.
• Property Sets: Enable "Export Revit property sets" and "Export IFC common property sets" to include both Revit-native and standard IFC properties.
• Base quantities: Enable to export calculated quantities (area, volume, length) as IFC base quantities.

Common pitfall: Revit's default export mapping may not map all custom parameters. Use the IFC export setup dialog to create custom mappings for project-specific properties.

From Tekla Structures

Tekla exports IFC via File > Export > IFC. Tekla generally produces high-quality structural IFC files because its internal data model aligns well with IFC's structural entities.

Key considerations:

• Tekla maps its native element types directly to IFC structural entities (IfcBeam, IfcColumn, IfcPlate).
• Connection details and bolts can be exported but may not translate cleanly to all viewers.
• Use Tekla's IFC export organizer to control which objects and properties are included.

From Archicad

Archicad uses a translator-based system for IFC export. Translators define how Archicad elements map to IFC entities and which properties are exported.

Archicad provides pre-built translators for common scenarios (coordination, quantity takeoff, facility management). You can duplicate and customize these translators for project-specific requirements.

Common Quality Issues with IFC Exports

Missing Properties

The most frequent issue. An element has data in the native BIM tool, but that data does not appear in the IFC export. Causes include:

• Properties not mapped to IFC property sets in the export configuration
• Custom parameters that have no IFC equivalent without manual mapping
• Classification data stored in a format the exporter does not recognize

Geometry Loss or Simplification

Complex geometry sometimes degrades during IFC export. Curved walls may become faceted, sloped slabs may lose their exact profile, and MEP fittings may export as simplified bounding boxes instead of detailed geometry.

This happens because IFC supports multiple geometric representations (CSG, B-rep, swept solid, tessellated), and exporters may choose a less precise representation for performance or compatibility reasons.

Incorrect Spatial Assignment

Elements assigned to the wrong storey, or not assigned to any storey at all, create problems for downstream tools that rely on spatial structure for organization and analysis.

Duplicate GUIDs

Each IFC element should have a globally unique identifier (GUID). Some export workflows — particularly when exporting sub-models and merging them — can produce duplicate GUIDs, which confuse model comparison and change detection tools.

How to Validate IFC Files

Validation catches export issues before they affect downstream workflows. There are several approaches:

Schema Validation

Check that the IFC file conforms to the IFC schema — all entities have required attributes, relationships are well-formed, and data types are correct. Tools like the buildingSMART IFC Validation Service perform schema validation.

Content Validation

Schema validation tells you the file is syntactically correct, but not whether the content is meaningful. Content validation checks things like:

• Are all elements assigned to a spatial structure?
• Do elements have the required property sets for the project?
• Are material assignments present and correctly structured?
• Are quantities consistent with geometry?

Automated quality control pipelines can run these checks systematically on every model upload. Platforms like Viralution support configurable QC rules that validate IFC content against project-specific requirements.

Visual Inspection

Open the IFC file in a viewer separate from the authoring tool. Elements that look correct in Revit or Tekla may render differently in an IFC viewer because the viewer interprets only what is in the IFC file, not the native model data.

Compare the IFC model against the native model. Look for missing elements, incorrect colors or materials, and geometry that appears simplified or distorted.

Best Practices for IFC Workflows

1. Agree on an IFC version at project kickoff. Mixing IFC2x3 and IFC4 in the same project creates compatibility headaches.
2. Define required property sets early. Document which properties must be present in IFC exports and create export configurations that include them.
3. Test exports with a small model first. Before exporting the full project model, export a single floor or discipline to verify that properties, geometry, and spatial structure transfer correctly.
4. Automate validation. Manual inspection does not scale. Set up automated checks that run on every IFC upload to catch issues immediately.
5. Version your export configurations. When export settings change, track those changes. A configuration that worked last month may produce different results after a software update.
6. Keep the original native models. IFC is an exchange format, not a replacement for native models. Always retain the Revit, Tekla, or Archicad source files as the authoritative source.
7. Be aware of file size implications. IFC files can grow large, particularly when tessellated geometry is used instead of parametric representations. A Revit model that is 200 MB natively may produce an IFC file of 400 MB or more, depending on export settings. High-detail exports with tessellated geometry for every element increase file size significantly. For coordination purposes, consider exporting at moderate detail levels and reserving high-detail exports for fabrication or visualization workflows where geometric precision justifies the larger file.
8. Document your export workflow. Record which export settings, property mappings, and IFC version you used for each project milestone. When issues arise months later — a property missing from the IFC, geometry that does not match the native model — having a documented export workflow makes diagnosis faster than recreating settings from memory.