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IFC Import and Export

In one sentence: IFC (Industry Foundation Classes) is the open standard format for exchanging BIM data between applications — understanding the difference between Classic and Native IFC modes, and how to prepare a model for clean exchange, determines whether other software can correctly read your FreeCAD model.

What is IFC?

IFC (Industry Foundation Classes) is an open, neutral file format maintained by buildingSMART International for sharing building and infrastructure data. Unlike DXF (geometry only) or PDF (presentation only), an IFC file carries:

  • Geometry — the 3-D shape of each element.
  • Semantics — what each element is (wall, column, door, slab, pipe).
  • Properties — physical and functional data (fire rating, material, load bearing, thermal transmittance).
  • Relationships — containment (element is in this storey), adjacency (wall meets wall), hosting (door is in this wall).
  • Quantities — computed measurements (area, volume, length).

Common IFC versions in use: IFC 2×3 (most widely supported), IFC 4 (current standard), IFC 4.3 (infrastructure extension).

Two IFC modes in FreeCAD

FreeCAD BIM supports two approaches to IFC. They are fundamentally different in how the document relates to the IFC data.

Classic IFC

Step What happens
Import IFC entities are read and converted to FreeCAD objects
Edit Work with FreeCAD-native objects (Wall, Column, etc.)
Export FreeCAD objects are converted back to IFC and written to a file

Classic IFC is useful for viewing and lightly editing imported models. The conversion step means that some IFC data (custom property sets, complex geometry types) may not round-trip perfectly.

Step What happens
Open / import The IFC file is loaded as-is; every IFC entity becomes a FreeCAD object that is that IFC entity
Edit Modifying geometry or properties modifies the underlying IFC entity directly
Save Writes the modified IFC file back — no conversion step

Native IFC preserves all IFC data including custom property sets, IFC GUIDs, and complex geometry types. Use it for all new projects intended for BIM collaboration.

To start a Native IFC project: File → New then use the BIM workbench tools directly — the document is automatically kept in sync with the IFC model. To open an existing IFC file natively: File → Open and select an .ifc file.

The Site → Building → Level hierarchy

IFC requires every element to be contained in a spatial structure:

IfcProject
 └── IfcSite
      └── IfcBuilding
           └── IfcBuildingStorey (Level)
                └── IfcSpace (optional)
                     └── IfcWall / IfcColumn / IfcBeam / ...

This hierarchy is not optional — it is a requirement of the IFC schema. An element that is not assigned to a storey will either fail Preflight or be silently dropped by receiving applications.

Create the hierarchy first using Site, Building, and Level before adding walls and other elements.

IFC class assignments

Every FreeCAD BIM object must have an IFC class assigned. The class determines how receiving software interprets the element:

FreeCAD object Typical IFC class Notes
Wall IfcWall or IfcWallStandardCase Standard for straight walls
Column IfcColumn Vertical load-bearing member
Beam IfcBeam Horizontal load-bearing member
Slab IfcSlab Floor, ceiling, or roof plate
Door IfcDoor Must be hosted by a wall
Window IfcWindow Must be hosted by a wall
Equipment IfcBuildingElementProxy Generic catch-all for non-standard elements

Change IFC class assignments using IFC Elements — the spreadsheet-style panel that lists all objects with their current class.

Wrong IFC class causes incorrect behaviour in receiving software

A structural column exported as IfcWall will be treated as a wall by structural analysis software — with incorrect load path assumptions. A door exported as IfcBuildingElementProxy will not be recognised as an opening by energy analysis software.

Property sets (Pset_*)

IFC elements carry structured attribute groups called property sets. Standard property sets are defined by the IFC schema and named with the Pset_ prefix:

Property set Applies to Key properties
Pset_WallCommon IfcWall IsExternal, LoadBearing, ThermalTransmittance
Pset_SlabCommon IfcSlab IsExternal, LoadBearing
Pset_DoorCommon IfcDoor IsExternal, FireRating, AcousticRating
Pset_ConcreteElementGeneral Concrete ConstructionMethod
Pset_BuildingElementProxyCommon Proxy Reference

Attach and edit property sets using IFC Properties.

FreeCAD Data-panel properties are NOT IFC property sets

Properties you add via the FreeCAD Properties panel (Data tab) are FreeCAD-internal properties. They are not written to IFC export. Use the IFC Properties panel to attach standard Pset_* sets.

Quantities

IFC BaseQuantities are standardised geometric measurements (area, volume, length) that receiving applications can use directly without recomputing from geometry. FreeCAD computes these automatically.

Check computed quantities with IFC Quantities before export.

Export workflow

  1. Build the spatial hierarchy — Site → Building → Level, then place all elements in a Level.
  2. Assign IFC classes — use IFC Elements to verify every object has the correct class.
  3. Add required property sets — use IFC Properties to attach Pset_* sets for fire rating, load bearing, etc.
  4. Run Preflight — Preflight checks hierarchy, classes, solid geometry, hosted openings, and materials.
  5. Export — File → Export → IFC (.ifc or .ifczip).

Common Preflight failures and fixes

Preflight check Failure Fix
IFC hierarchy Element not in a storey Move element inside a Level object
IFC classes Object has generic class IfcBuildingElement Assign a specific class in IFC Elements
Solid geometry Object produces an invalid mesh Check the FreeCAD shape for errors; use Part → Check Geometry
Openings Door/window not hosted by a wall Select the door/window, then BIM → Add/Remove host to assign it to a wall
Materials Structural element has no material Assign a material via Manage → Material

Import workflow

  1. File → Open and select an .ifc file (or File → Import to import into an existing document).
  2. In the import dialog, choose Native IFC or Classic IFC mode.
  3. For large files, use the import options to filter which storey or IFC class to import (avoids loading the entire model).
  4. After import, inspect the model tree — each IfcBuildingStorey becomes a Level, each wall/column/beam becomes its corresponding BIM object.

Large IFC files can be slow to load

IFC files from other BIM applications often contain thousands of elements. Use the import filter to load only the storey or discipline you need.

Complex geometry may import as mesh

Swept profiles, computational geometry, and non-standard IFC geometry types that FreeCAD cannot parametrically reconstruct are imported as mesh representations. They are read-only (cannot be dimensionally edited).

Python API

import importIFC
import FreeCAD as App

# Import an IFC file (Classic IFC mode)
importIFC.open("/path/to/model.ifc")

# Export the current document to IFC
import exportIFC
doc = App.ActiveDocument
exportIFC.export(doc.Objects, "/path/to/output.ifc")

For Native IFC, the file is the document — use App.openDocument():

doc = App.openDocument("/path/to/native_model.ifc")
# Edit objects...
doc.save()   # writes back to the .ifc file

See also