Use when working with IFC files in FreeCAD, importing BIM models, or doing round-trip IFC editing. Prevents the common mistake of using legacy import instead of NativeIFC mode or losing IFC data during FreeCAD conversion. Covers FreeCAD 1.0+ BIM Workbench, NativeIFC mode, IfcOpenShell integration, import/export workflows, and round-trip editing patterns. Keywords: FreeCAD, IFC, NativeIFC, BIM Workbench, IfcOpenShell, round-trip, FreeCAD BIM, IFC import, IFC export, Arch module, edit IFC in FreeCAD, open IFC file, FreeCAD BIM modeling, free BIM software.
Use when working with IFC files in FreeCAD, importing BIM models, or doing round-trip IFC editing. Prevents the common mistake of using legacy import instead of NativeIFC mode or losing IFC data during FreeCAD conversion. Covers FreeCAD 1.0+ BIM Workbench, NativeIFC mode, IfcOpenShell integration, import/export workflows, and round-trip editing patterns. Keywords: FreeCAD, IFC, NativeIFC, BIM Workbench, IfcOpenShell, round-trip, FreeCAD BIM, IFC import, IFC export, Arch module, edit IFC in FreeCAD, open IFC file, FreeCAD BIM modeling, free BIM software.
license
MIT
compatibility
Designed for Claude Code. Requires FreeCAD 1.0+ with BIM Workbench and IfcOpenShell 0.8.x.
metadata
{"author":"OpenAEC-Foundation","version":"1.0"}
crosstech-impl-freecad-ifc-bridge
Quick Reference
FreeCAD IFC Modes
Mode
FreeCAD Version
IFC Engine
Data Loss
Round-Trip
NativeIFC Locked
1.0+
IfcOpenShell 0.8.x
NONE
Lossless
NativeIFC Unlocked
1.0+
IfcOpenShell 0.8.x
NONE (IFC part)
Lossless
Legacy Import/Export
< 1.0 / 1.0+ fallback
IfcOpenShell
YES
Lossy
BIM Workbench Tools (FreeCAD 1.0+)
Tool
Purpose
IFC Elements Manager
Control which elements export to IFC
IFC Properties Manager
Manage property set attachments
IFC Quantities Manager
Handle explicit quantity exports
IFC Explorer
Pre-import structural analysis
IFC Diff
Visual comparison of two IFC files
Critical Warnings
ALWAYS use NativeIFC mode for IFC workflows. Legacy import converts IFC to FreeCAD Part objects, losing parametric IFC data permanently.
NEVER save an IFC file opened in NativeIFC locked mode as .FCStd — the IFC file IS the document. Saving as .FCStd breaks the NativeIFC link.
NEVER mix NativeIFC locked mode with non-IFC geometry. Use unlocked mode when combining IFC and non-IFC elements in one document.
ALWAYS verify IfcOpenShell version compatibility with FreeCAD. Mismatched versions cause silent import failures. Check with import ifcopenshell; print(ifcopenshell.version).
NEVER use the legacy importIFC module for new projects. Use the BIM Workbench NativeIFC workflow instead.
ALWAYS load shapes on demand for large IFC files (100MB+). NativeIFC supports selective geometry loading to manage memory.
Entities inherit from IfcRoot (GlobalId, Name, Description, OwnerHistory)
Relationships are objectified (IfcRelAggregates, IfcRelContainedInSpatialStructure)
Types shared via IfcRelDefinesByType
Materials assigned via IfcRelAssociatesMaterial
The Bridge: NativeIFC / Traditional Import-Export
NativeIFC (PREFERRED): The IFC file IS the FreeCAD document. No conversion happens. IfcOpenShell reads and writes IFC data directly. FreeCAD renders shapes on demand using IfcOpenShell's OpenCASCADE geometry converter.
Traditional Import: IfcOpenShell parses IFC geometry and converts it to FreeCAD Part::TopoShape objects. This is a one-way conversion that loses IFC semantic data unless explicitly mapped to FreeCAD properties.
Traditional Export: FreeCAD BIM objects are serialized to IFC entities using IfcOpenShell. BIM type mappings (Arch.Wall -> IfcWall) are applied automatically. Non-BIM objects are excluded unless explicitly converted.
ALWAYS prefer NativeIFC mode over legacy import/export for IFC workflows.
ALWAYS check IfcOpenShell availability before IFC operations: import ifcopenshell.
ALWAYS use locked NativeIFC mode when the IFC file is the single source of truth.
ALWAYS use unlocked NativeIFC mode when mixing IFC with non-IFC elements.
ALWAYS load shapes selectively for large models — NativeIFC supports on-demand loading.
ALWAYS verify schema version with ifcopenshell.open(path).schema before processing.
NEVER assume FreeCAD preserves IFC parametric geometry in legacy mode — it converts to BREP.
NEVER edit IFC files outside FreeCAD while they are open in NativeIFC locked mode.
NEVER rely on FreeCAD-specific parametric constraints surviving IFC export — Sketcher constraints and Part constraints are NOT part of IFC.
NEVER use importIFC.export() for NativeIFC workflows — save the document directly.
Decision Tree
START: You need to work with IFC in FreeCAD
|
+-- Q1: Is FreeCAD 1.0+ available?
| +-- YES --> Use BIM Workbench with NativeIFC
| +-- NO --> Use legacy Arch import/export (expect data loss)
|
+-- Q2: What is the workflow?
| +-- View/inspect IFC --> NativeIFC locked mode (read-only is fine)
| +-- Edit IFC and save back --> NativeIFC locked mode
| +-- Combine IFC with non-IFC geometry --> NativeIFC unlocked mode
| +-- Create BIM model from scratch --> BIM Workbench, export to IFC
| +-- One-time geometry extraction --> Legacy import is acceptable
|
+-- Q3: Is the IFC file large (>100MB)?
| +-- YES --> Use NativeIFC with selective shape loading
| +-- NO --> Full shape loading is acceptable
|
+-- Q4: Is round-trip fidelity required?
| +-- YES --> NativeIFC locked mode ONLY
| +-- NO --> Legacy export is acceptable for one-way conversion
|
+-- Q5: Do you need scripting access to IFC data?
+-- YES, to IFC entities --> Use ifcopenshell directly on the file
+-- YES, to FreeCAD objects --> Use FreeCAD.ActiveDocument.Objects
+-- YES, to both --> NativeIFC mode (objects ARE IFC entities)
Essential Patterns
Pattern 1: Open IFC in NativeIFC Locked Mode
import FreeCAD
# Open IFC file directly — NativeIFC treats it as the document
doc = FreeCAD.openDocument("/path/to/model.ifc")
# Iterate IFC objectsfor obj in doc.Objects:
ifhasattr(obj, "IfcType"):
print(f"{obj.Label}: {obj.IfcType}")
# Modify an element
wall = doc.getObjectsByLabel("Exterior Wall 01")[0]
wall.Label = "Renamed Wall"# Save — writes directly to the IFC file, minimal diff
doc.save()
Pattern 2: Access IFC Data via IfcOpenShell (NativeIFC)
import FreeCAD
import ifcopenshell
import ifcopenshell.util.element
# Open the IFC file with IfcOpenShell for semantic queries
ifc_file = ifcopenshell.open("/path/to/model.ifc")
# Query all walls with their propertiesfor wall in ifc_file.by_type("IfcWall"):
psets = ifcopenshell.util.element.get_psets(wall)
name = wall.Name or"Unnamed"
is_external = psets.get("Pset_WallCommon", {}).get("IsExternal", None)
print(f"{name}: external={is_external}")
# Check schema versionprint(f"Schema: {ifc_file.schema}") # "IFC2X3", "IFC4", "IFC4X3"
Pattern 3: Create BIM Objects and Export to IFC
import FreeCAD
import Arch
import Draft
# Create a new document
doc = FreeCAD.newDocument("BIM_Project")
# Create BIM objects using the Arch module
wall = Arch.makeWall(length=5000, width=200, height=3000)
wall.IfcType = "IfcWall"
wall.Label = "Exterior Wall 01"# Create a slab
slab = Arch.makeStructure(length=6000, width=5000, height=200)
slab.IfcType = "IfcSlab"
slab.Label = "Ground Floor Slab"# Recompute to update geometry
doc.recompute()
# Export to IFC using the legacy exporterimport importIFC
importIFC.export([wall, slab], "/path/to/output.ifc")
import FreeCAD
import Arch
# Create document with mixed content
doc = FreeCAD.newDocument("Mixed_Project")
# Add non-IFC geometry (parametric FreeCAD part)import Part
box = doc.addObject("Part::Box", "SiteContext")
box.Length = 10000
box.Width = 10000
box.Height = 100# Add IFC project (unlocked mode — IFC and non-IFC coexist)# The IFC project attaches to a separate .ifc file# Non-IFC objects (like the box) remain in the .FCStd file
doc.recompute()
Pattern 5: Selective Shape Loading for Large Models
import FreeCAD
# Open large IFC file — NativeIFC loads metadata only
doc = FreeCAD.openDocument("/path/to/large_model.ifc")
# Shapes are loaded on demand per object# Access an object to trigger shape loading
obj = doc.getObjectsByLabel("Foundation Wall")[0]
shape = obj.Shape # Triggers geometry computation via IfcOpenShell# For batch processing without visualization, avoid loading shapesfor obj in doc.Objects:
ifhasattr(obj, "IfcType"):
# Access metadata only — no shape loadingprint(f"{obj.Label}: {obj.IfcType}")
Common Operations
Import/Export Operations
Operation
NativeIFC (Preferred)
Legacy
Open IFC
FreeCAD.openDocument("f.ifc")
File > Import > IFC
Save IFC
doc.save() (writes to .ifc)
importIFC.export(objs, "f.ifc")
Access properties
Via IfcOpenShell on same file
Custom properties on FreeCAD object
Round-trip edit
Direct — changes write to IFC
Lossy — re-export required
Large file handling
Selective shape loading
Full load into memory
FreeCAD BIM Type Mapping
FreeCAD BIM Object
IFC Entity
Notes
Arch.makeWall()
IfcWall
Maps directly
Arch.makeStructure()
IfcColumn / IfcBeam / IfcSlab
Based on IfcType property
Arch.makeWindow()
IfcWindow / IfcDoor
Based on IfcType property
Arch.makeStairs()
IfcStair
Maps directly
Arch.makeRoof()
IfcRoof
Maps directly
Arch.makePipe()
IfcPipeSegment
Maps directly
Arch.makeSite()
IfcSite
Spatial element
Arch.makeBuilding()
IfcBuilding
Spatial element
Arch.makeFloor()
IfcBuildingStorey
Spatial element
Data Preservation Matrix
Data Type
NativeIFC
Legacy Import
Legacy Export
IFC entity class
FULL
FULL
FULL
GlobalId
FULL
Stored as property
Generated new
Property sets
FULL
Partial (custom props)
Partial
Quantities
FULL
Partial
Partial
Relationships
FULL
Simplified
Simplified
Parametric geometry
FULL
Converted to BREP
From BREP
Material layers
FULL
Simplified
Simplified
Spatial hierarchy
FULL
Collection hierarchy
Regenerated
FreeCAD constraints
N/A
N/A
LOST
Sketcher data
N/A
N/A
LOST
Scripting Quick Reference
# Check FreeCAD versionimport FreeCAD
print(FreeCAD.Version()) # ['1', '0', '0', ...]# Check IfcOpenShell versionimport ifcopenshell
print(ifcopenshell.version) # "0.8.0" or similar# Check if NativeIFC is availabletry:
import nativeifc
NATIVEIFC_AVAILABLE = Trueexcept ImportError:
NATIVEIFC_AVAILABLE = False# Get all IFC objects in current document
doc = FreeCAD.ActiveDocument
ifc_objects = [o for o in doc.Objects ifhasattr(o, "IfcType")]
# Access underlying IfcOpenShell entity (NativeIFC)import ifcopenshell
ifc_file = ifcopenshell.open(doc.FileName)
entity = ifc_file.by_id(42) # Access by expressID
