IFC Files Are Heavy and Unreadable? Let's Debunk This Myth

Introduction

If you’ve worked in the BIM industry for any length of time, you’ve likely heard the criticism: “IFC files are too heavy,” “the structure is incomprehensible,” “it’s not practical for real projects.” These objections surface regularly in project meetings, software selection discussions, and online forums.

As someone who works daily with both authoring tools and IFC data, I find these arguments fascinating—not because they’re entirely wrong, but because they fundamentally misunderstand what IFC is designed to do. Let me take you through a more nuanced perspective.

What IFC Is Not

Before we discuss what IFC actually is, let’s clear up some common misconceptions that fuel the “heavy and complex” narrative.

IFC is not a proprietary file format. Unlike .rvt, .pln, or .dwg, IFC doesn’t belong to any software vendor. It’s an open international standard (ISO 16739-1:2024), developed and maintained by buildingSMART International under a Creative Commons license. This openness is precisely why it exists.

IFC is not optimized for authoring. You’re not meant to design in IFC. Your authoring tool (Revit, ArchiCAD, Allplan, etc.) uses its native format for a reason—it’s optimized for that specific workflow. IFC serves a different purpose: exchange and archival.

IFC is not just geometry. This is perhaps the most critical misunderstanding. When people complain about “heavy” IFC files, they’re often thinking of IFC as a 3D model format. But IFC encodes far more: relationships between elements, material properties, classification references, spatial hierarchies, ownership chains, and even scheduling data. Comparing an IFC file to a mesh export is like comparing a spreadsheet to a photograph—they serve fundamentally different purposes.

Understanding IFC Structure

The IFC schema is built on EXPRESS, a data modeling language defined in ISO 10303 (STEP standard). This lineage matters because EXPRESS was designed for industrial data exchange where precision and interoperability are paramount—think aerospace and automotive manufacturing.

According to buildingSMART’s technical documentation:

“The IFC schema is a standardized data model that codifies, in a logical way, the identity and semantics, characteristics or attributes, and relationships of objects, abstract concepts, processes, and people.”

The schema organizes information into layers:

1. Core Layer — Fundamental concepts applicable across domains
2. Shared Layer — Elements common to multiple disciplines (walls, doors, spaces)
3. Domain Layer — Specialized entities for specific industries (HVAC, structural, electrical)
4. Resource Layer — Supporting definitions (geometry, materials, quantities)

This hierarchy isn’t arbitrary complexity—it’s structured complexity that enables a building’s entire lifecycle information to be captured in a vendor-neutral way.

Does Complexity Affect Performance?

Let’s address the elephant in the room: yes, IFC files can be large, and yes, parsing them requires computational resources. But context matters enormously.

File Format Comparison

buildingSMART publishes comparative data on IFC encoding formats. Taking STEP Physical File (.ifc) as the baseline:

Source: buildingSMART Technical - IFC Formats

The standard .ifc format (STEP Physical File) offers the best balance of compatibility and size for file-based exchange. If size is critical, .ifcZIP reduces files to roughly 17% of original size with no data loss.

Why Files Grow

An IFC file’s size is determined by:

1. Geometric complexity — Tessellated representations (meshes) are larger than parametric definitions
2. Level of detail — A fully-detailed construction model vs. a coordination model
3. Export settings — Many authoring tools include unnecessary data by default
4. Property richness — Models with extensive metadata are larger, but that’s the point

The real question isn’t “why is this file large?” but rather “what information does this file contain that I actually need?”

Geometry Generation from IFC Data

When you open an IFC file in a viewer, the software must parse the textual schema and generate renderable geometry. This process—not the file size itself—is often the bottleneck users perceive as “slowness.”

IFC supports multiple geometric representations:

• Boundary Representation (BREP) — Precise but computationally expensive
• Swept Solids — Efficient for linear elements like beams and pipes
• Tessellated Geometry — Pre-computed meshes, fast to render but larger files
• Constructive Solid Geometry (CSG) — Boolean operations on primitives

Different software implementations handle these representations with varying efficiency. A well-optimized viewer can stream geometry progressively, while a poorly implemented one might attempt to load everything into memory simultaneously.

Viewer Performance Varies Widely

The buildingSMART software implementation database lists over 480 tools supporting IFC in various capacities. Performance varies significantly:

Dedicated IFC viewers (like BIMvision, Solibri, or xBIM) are specifically optimized for parsing and rendering IFC data. They employ techniques like:

• Lazy loading of geometry
• Level-of-detail switching based on zoom
• Spatial indexing for faster queries
• GPU-accelerated rendering

General-purpose CAD tools importing IFC often convert it to their internal format first, adding overhead. This is a tool limitation, not an IFC limitation.

Web-based viewers using libraries like IFC.js or xeokit can now handle substantial models directly in the browser, demonstrating that performance issues are increasingly about implementation, not inherent format limitations.

Methods for Accelerating IFC Workflows

If you’re experiencing genuine performance issues with IFC, consider these practical approaches:

1. Model View Definitions (MVD)

Not every exchange needs the full IFC schema. MVDs define subsets for specific use cases:

• Reference View — Lightweight, read-only geometry for coordination
• Design Transfer View — Editable elements with semantic integrity
• Alignment View — Infrastructure-focused subset for linear assets

Exporting to appropriate MVDs reduces file size and processing requirements significantly.

2. Federation Over Monolithic Files

Rather than one massive IFC file, consider federating multiple discipline-specific models. Modern platforms (Bimplus, Trimble Connect, Autodesk Construction Cloud) handle federation natively, loading only relevant portions as needed.

3. IFC Validation Before Exchange

buildingSMART’s IFC Validation Service can identify structural issues in your exports that might cause downstream performance problems. Invalid references, orphaned entities, and redundant definitions all contribute to bloated, slow-to-parse files.

Validation Service: validate.buildingsmart.org

4. Compression for Archival

For long-term storage or transmission over limited bandwidth, .ifcZIP offers substantial size reduction. Most modern tools support this format natively.

5. Choose Appropriate Tools

For regular IFC review and coordination, invest in purpose-built viewers rather than forcing authoring tools to do a job they weren’t designed for. Many excellent options are free:

• BIMvision (free, Windows)
• Solibri Anywhere (web-based)
• xBIM Xplorer (open source)
• IFC.js based viewers (web, open source)

Conclusion

The “IFC is heavy and complex” narrative persists because it contains a grain of truth wrapped in fundamental misunderstanding. Yes, comprehensive building data produces larger files than simple geometry exports. Yes, the schema is sophisticated because it models sophisticated reality.

But these aren’t failures—they’re features. IFC exists to solve a genuine industry problem: vendor lock-in and data loss across the building lifecycle. The fact that over 480 software tools now support it, that it’s an ISO standard, and that projects worldwide mandate its use speaks to its success.

As BIM coordinators, our role isn’t to avoid complexity but to manage it intelligently. Choose appropriate MVDs, validate your exports, select proper tools for the task, and remember that the richness of IFC data serves the entire project team—not just today’s modeler.

The next time someone dismisses IFC as “too heavy,” ask them: “Compared to what, and for what purpose?” That’s where the real conversation begins.