A below-grade structure. An underground car park built to WU concrete specification — Wasserundurchlässig, AWF02-C25-30-WU-BIM. Waterproof concrete. Certified mix design. Specialist placement. Premium pricing.
It is also a mixed-authoring environment. Structural and non-structural systems coexist under identical IFC classes. Masonry walls. Plasterboard ceilings. Insulation systems. Natural stone finishes. All exported as IfcWallStandardCase and IfcSlab. Sanitary fixtures exported as IfcBuildingElementProxy. No LoadBearing flags. No explicit structural separation anywhere in the file.
A standard extraction treats everything as potential concrete. Reported concrete volume — 94.074 m³. Correct concrete volume — 62.703 m³. Overstatement — 31.371 m³. Error — 50%. The required classification signals were present in the IFC. Not in standard fields.
- 63 total IFC elements
- 14 structural concrete elements
- 62.703 m³ validated concrete volume
- 4 concrete downstand beams — Unterzug
- 2 concrete slabs — DEF04-C25-30-BIM, 250mm
- 8 structural concrete walls — 7 external WU specification (AWF02-C25-30-WU-BIM), 1 internal (IWF02-C25-30-BIM)
- 23 non-structural walls — masonry, plasterboard, insulation, finishes
- 3 non-structural slabs — mineral wool, plasterboard
- 4 sanitary fixture proxies — sink, toilet, washbasin, washing machine
- Zero IfcReinforcingBar — steel quantities ratio estimated
Every material layer in every Allplan wall carries a field called Gewerk. Construction trade assignment. It is stored in IfcComplexProperty Object Layer Attributes nodes — not in standard IFC property sets. Engines built around IfcPropertySingleValue and standard Psets do not read it.
31.371 m³ of masonry, plasterboard, insulation, and stone finish entered the BOQ because this field was not read. The Gewerk values in this file are unambiguous author-assigned construction classification — the most authoritative classification signal in the file.
| Gewerk Value | Trade | Decision |
|---|---|---|
| Betonarbeiten | Concrete works | Include |
| Mauerarbeiten | Masonry works | Exclude |
| Trockenbauarbeiten | Dry construction / plasterboard | Exclude |
| Putz- und Stuckarbeiten | Plaster and stucco | Exclude |
| Abdichtung gegen Wasser | Waterproofing | Exclude |
| Wärmedämmung | Thermal insulation | Exclude |
| Natursteinarbeiten | Natural stone finish | Exclude |
After Gewerk-based filtering — 62.703 m³. Validated to 4 decimal places. The IFC did not fail. The extraction system simply did not read the part of the file that contained the classification truth.
Eight concrete walls are multi-layer assemblies. One IFC element. Multiple material layers. One combined NetVolume that includes all of them. Extracting NetVolume directly and pricing it as concrete is incorrect.
Wall 3 — the clearest example. Concrete layer AWF02-C25-30-WU-BIM at 300mm is the structural element. Waterproofing layer FAS2-DRW-DAE at 120mm is excluded by Gewerk. Total assembly build-up — 420mm.
Extracting NetVolume directly overstates this element by 40%. This fractional decomposition was applied to all 7 multi-layer concrete walls. All confirmed against Bonsai to 4 decimal places. The IFC volume is the assembly total — not the structural concrete volume.
Wall 20 — AWF02-C25-30-WU-BIM — a waterproof external concrete wall. GrossVolume 3.433 m³. NetVolume 1.313 m³. Opening removal — 2.120 m³ — 61.7% of gross volume. More than half of this wall's gross volume does not exist.
A GrossVolume-based workflow overstates concrete on this element by 161%. The commercial consequence is specific to this material. WU concrete is a regulated specification in German construction practice. It requires certified mix design, independent inspection, and specialist placement. It is priced at a premium. Pricing the gross volume of a WU concrete wall means paying premium rates for concrete that was never poured.
NetVolume used throughout. Opening subtractions confirmed correct on all elements.
Four IfcBuildingElementProxy elements in the file. A sink. A washbasin. A toilet. A washing machine. Identified via Objektname: Sanitär in Allplan Attributes. Unit — St, pieces, not volume. Zero structural relevance.
Without Objektname reading these appear in the BOQ labeled as Concrete (assumed). A washing machine labeled as a structural concrete element in an engineering report destroys trust in every number that follows it. All four correctly excluded after Objektname classification implemented.
14 concrete elements validated against IFC data in Bonsai/BlenderBIM. Gewerk extraction from IfcComplexProperty, fractional layer decomposition, and Objektname-based proxy detection combined to remove 31.371 m³ of non-structural contamination.
These are the actual StructBOQ outputs generated from this IFC file. No data has been modified. Cost figures use default rates (€120/m³ concrete, €1.2/kg steel) and are indicative only — not market rates. Download and open to inspect the full element-level breakdown, confidence scoring, and validation findings.
Generated by StructBOQ v3.3 · shabirbim.com · Outputs are unmodified engine results
Steel reinforcement is not modeled in this file. All steel quantities are ratio estimated from BS EN 1992. Uncertainty range ±50 to 300%. This is a waterproof concrete underground structure — actual reinforcement density in WU walls is project-specific and cannot be estimated reliably from ratios. Do not use for procurement, fabrication, or contractual pricing.
This is a German IFC model. Allplan. IFC2X3. Underground car park. WU concrete specification. The classification system is trade-based — Gewerk defines construction responsibility, Objektname defines semantic object intent, IfcComplexProperty carries authoritative layer-level meaning.
Standard IFC extraction engines built around Revit conventions miss this entirely. Without reading these signals — structural and non-structural systems collapse into one category, waterproof concrete is priced alongside insulation and masonry, and BOQ inflation reaches 50% in a 63-element file.
The IFC did not fail. The extraction system simply did not read the part of the file that contained the classification truth.