BIM is FreeCAD's architectural-design workbench — building walls, doors, windows, structural members, and producing IFC files compatible with Revit, ArchiCAD, and the rest of the Building Information Modeling ecosystem. It is the open-source path for architects who don't want to pay $2,500/year for Revit, plus the path for hobbyists designing tiny houses, sheds, and DIY home renovations without a commercial subscription.

This page is the practical reference. BIM is a deep specialty — full architectural practice involves regulations, sheets sets, scheduling, and rendering pipelines that this guide doesn't cover. But for understanding what FreeCAD BIM can do and how to start a project, it's the right starting point.

What BIM is (and isn't)

BIM (Building Information Modeling) is more than 3D — it's a way of modeling buildings where each element carries semantic meaning. A wall isn't just a rectangular solid; it's a Wall object with a thickness, height, material, fire rating, and acoustic class. A window knows it's a window, what manufacturer specified it, what its U-value is. Schedules and drawings derive automatically from the model rather than being drawn separately.

FreeCAD BIM workbench (formerly the Arch workbench) implements this model. Industry Foundation Classes (IFC) is the standardized exchange format — vendor-neutral, supported by every major BIM tool. FreeCAD reads and writes IFC, which means a FreeCAD-modeled building can be opened in Revit, and a Revit project can be opened in FreeCAD.

The BIM workflow at a high level

1. Set up the project: site, building, levels (ground floor, first floor, roof).
2. Walls: external perimeter and internal partitions. From sketches or 2D outlines.
3. Doors and windows: openings drilled into walls. From the parametric library or imported families.
4. Structural elements: columns, beams, slabs, foundations.
5. Spaces: rooms with area and volume calculations.
6. Annotations: dimensions, labels, materials.
7. Drawings: floor plans, sections, elevations via TechDraw integration.
8. IFC export for handoff to engineers, contractors, regulators.

Walls — the foundational element

A Wall is a 2D path extruded vertically with a thickness. Three ways to create one:

• From sketch: draw the wall path in Sketcher, then BIM → Wall. Most flexible.
• From line: select a line in Draft workbench, BIM → Wall. Quickest for simple straight walls.
• From scratch: BIM → Wall, then click two points. Default thickness 200mm, height 2400mm.

Wall properties: Length, Width (thickness), Height, Alignment (centerline / left / right), Material. Multi-material walls (e.g., brick + insulation + drywall) use the Multi-Material Wall variant where you stack layers with their own properties.

Doors and windows

Doors and windows are parametric components that punch openings in their host wall. The opening is automatic — drag a window onto a wall, the wall's geometry subtracts a hole around the window automatically. Move the window, the hole moves with it.

FreeCAD BIM ships a small library of parametric door and window types. For more variety, install the BIM Components addon — adds dozens of standardized European and US window styles (single-hung, casement, awning, sliding) with adjustable dimensions.

IFC import brings in the door/window library from the source project (Revit, ArchiCAD, etc.). Edits stay parametric — change the dimension, the model rebuilds.

Structural elements

• Columns: vertical structural members. Rectangular, circular, or custom profile.
• Beams: horizontal structural members. Profile selectable from the steel/concrete library (W-shapes, HSS, IPE, HEA, etc.).
• Slabs: floors and ceilings. From a 2D sketch + thickness.
• Foundations: footings, slabs-on-grade. Specialized variants of slabs.
• Trusses (via addon): parametric truss generators.
• Stairs: from rise/run/width parameters or from sketched footprint.

Each element has structural properties (material, profile dimensions, load-bearing classification) that travel through IFC export to structural-engineering tools.

Spaces and schedules

A Space object marks an enclosed volume — a room. Define by selecting bounding faces (wall surfaces, floor, ceiling) or by drawing a 2D boundary. The Space calculates floor area and volume automatically.

Schedules: BIM workbench supports IFC-style schedules — query the model for "all walls thicker than 200mm" or "all windows in Building A, first floor" and output the result to a spreadsheet or drawing.

IFC import and export

IFC (Industry Foundation Classes) is the standard exchange format for BIM. FreeCAD supports IFC2x3 and IFC4 — the two versions most commonly used in practice. To import: File → Import → IFC. To export: File → Export → IFC.

IFC import preserves: walls, doors, windows, structural elements, spaces, materials, property sets. It does not preserve: vendor-specific scripted objects (Revit families with embedded code), drawing sheets, view definitions. For those you'd need the original vendor file.

IFC export from FreeCAD is generally clean — Revit, ArchiCAD, Solibri, BIMcollab all read FreeCAD-generated IFC files without complaints. Use it for handoff to consultants who use different tools.

Drawings — TechDraw integration

Floor plans, sections, elevations, and details come from the TechDraw workbench. Place the building model on a TechDraw sheet, set the view direction (top for plan, side for elevation, sliced plane for section), and TechDraw generates a 2D vector drawing that updates when the model changes.

Output formats: PDF (for printing), SVG (for editing in Inkscape), DXF (for handoff to AutoCAD users). Multiple sheets per project, automatic dimension generation, layered output for cleaner drawings.

When BIM workbench fits and when it doesn't

Fits well for:

• Hobbyist architects designing tiny homes, sheds, garages, additions.
• Small architecture practices doing residential work without a Revit budget.
• Consultants reading and modifying IFC files from larger BIM projects.
• Pre-design conceptual modeling before transitioning to a paid tool for documentation.

Falls short for:

• Large commercial projects that depend on a vendor-specific family library.
• Construction documentation where regulatory compliance requires specific drawing standards FreeCAD doesn't auto-enforce.
• Coordination workflows that assume cloud-based model sharing (Revit Cloud, BIM 360).
• MEP (mechanical, electrical, plumbing) layouts — BIM workbench has limited MEP support.

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