IFC Quantity Takeoff Extraction

Extract structured quantity data from BIM models (IFC, Revit) for cost estimation, material ordering, and progress tracking.

Business Case

Problem: Manual quantity takeoff is:

• Time-consuming (40-80 hours for medium project)
• Error-prone (human counting mistakes)
• Not repeatable (changes require full rework)
• Disconnected from design (no live updates)

Solution: Automated QTO from BIM that:

• Extracts all quantities in minutes
• Groups by type, level, zone
• Updates instantly with model changes
• Exports to Excel for pricing

ROI: 90% reduction in QTO time, near-zero counting errors

DDC Tools Used

┌──────────────────────────────────────────────────────────────────────┐
│                      QTO EXTRACTION PIPELINE                          │
├──────────────────────────────────────────────────────────────────────┤
│                                                                       │
│   INPUT                 CONVERT                 ANALYZE               │
│   ┌─────────┐          ┌─────────┐            ┌─────────┐            │
│   │ .rvt    │          │ DDC     │            │ Python  │            │
│   │ .ifc    │─────────►│Converter│───────────►│ pandas  │            │
│   │ .dwg    │          │         │            │         │            │
│   └─────────┘          └─────────┘            └─────────┘            │
│                              │                      │                 │
│                              ▼                      ▼                 │
│                        ┌─────────┐            ┌─────────┐            │
│                        │ .xlsx   │            │ Grouped │            │
│                        │ raw data│            │ QTO     │            │
│                        └─────────┘            └─────────┘            │
│                                                    │                  │
│   OUTPUT                                           ▼                  │
│   ┌─────────────────────────────────────────────────────────────┐   │
│   │  QTO Report                                                  │   │
│   │  • Element counts by type                                    │   │
│   │  • Areas (m², ft²)                                           │   │
│   │  • Volumes (m³, ft³)                                         │   │
│   │  • Lengths (m, ft)                                           │   │
│   │  • Weights (kg, tons)                                        │   │
│   │  • Grouped by level/zone/system                              │   │
│   └─────────────────────────────────────────────────────────────┘   │
│                                                                       │
└──────────────────────────────────────────────────────────────────────┘

CLI Commands

Revit to Excel (with BBox for volumes)

# Basic extraction
RvtExporter.exe "C:\Models\Building.rvt"

# Full extraction with bounding boxes (for volume calculations)
RvtExporter.exe "C:\Models\Building.rvt" complete bbox

# Include schedules (Revit's built-in QTO)
RvtExporter.exe "C:\Models\Building.rvt" complete bbox schedule

IFC to Excel

# Extract IFC data
IfcExporter.exe "C:\Models\Building.ifc"

# Output: Building.xlsx with all IFC entities

DWG to Excel (2D areas)

# Extract DWG blocks and areas
DwgExporter.exe "C:\Drawings\FloorPlan.dwg"

Python Implementation

import pandas as pd
import numpy as np
from pathlib import Path
import subprocess
from typing import List, Dict, Optional
from dataclasses import dataclass

@dataclass
class QuantityItem:
    """Single quantity line item"""
    category: str
    type_name: str
    count: int
    area: float = 0.0
    volume: float = 0.0
    length: float = 0.0
    weight: float = 0.0
    unit_area: str = "m²"
    unit_volume: str = "m³"
    unit_length: str = "m"
    level: str = ""
    zone: str = ""


class BIMQuantityExtractor:
    """Extract quantities from BIM models using DDC converters"""

    def __init__(self, converter_path: str):
        self.converter_path = Path(converter_path)

    def convert_model(self, model_path: str, options: List[str] = None) -> Path:
        """Convert BIM model to Excel"""

        model = Path(model_path)
        options = options or ["complete", "bbox"]

        # Determine converter
        ext = model.suffix.lower()
        converters = {
            '.rvt': 'RvtExporter.exe',
            '.rfa': 'RvtExporter.exe',
            '.ifc': 'IfcExporter.exe',
            '.dwg': 'DwgExporter.exe',
            '.dgn': 'DgnExporter.exe'
        }

        converter = self.converter_path / converters.get(ext, 'RvtExporter.exe')

        # Build command
        cmd = [str(converter), str(model)] + options

        # Execute
        result = subprocess.run(cmd, capture_output=True, text=True)

        if result.returncode != 0:
            raise RuntimeError(f"Conversion failed: {result.stderr}")

        # Return path to generated Excel
        xlsx_path = model.with_suffix('.xlsx')
        return xlsx_path

    def load_bim_data(self, xlsx_path: str) -> pd.DataFrame:
        """Load converted BIM data from Excel"""

        xlsx = Path(xlsx_path)
        if not xlsx.exists():
            raise FileNotFoundError(f"Excel file not found: {xlsx}")

        # Read main data sheet
        df = pd.read_excel(xlsx, sheet_name=0)

        # Clean column names
        df.columns = df.columns.str.strip()

        return df

    def extract_quantities(
        self,
        df: pd.DataFrame,
        group_by: str = "Type Name",
        include_categories: List[str] = None
    ) -> List[QuantityItem]:
        """Extract quantities grouped by type"""

        # Filter categories if specified
        if include_categories and 'Category' in df.columns:
            df = df[df['Category'].isin(include_categories)]

        # Group and aggregate
        quantities = []

        for (category, type_name), group in df.groupby(['Category', group_by]):
            item = QuantityItem(
                category=str(category),
                type_name=str(type_name),
                count=len(group)
            )

            # Extract area
            area_cols = ['Area', 'Surface Area', 'Gross Area', 'Net Area']
            for col in area_cols:
                if col in group.columns:
                    item.area = group[col].sum()
                    break

            # Extract volume
            vol_cols = ['Volume', 'Gross Volume', 'Net Volume']
            for col in vol_cols:
                if col in group.columns:
                    item.volume = group[col].sum()
                    break

            # Extract length
            len_cols = ['Length', 'Curve Length', 'Unconnected Height']
            for col in len_cols:
                if col in group.columns:
                    item.length = group[col].sum()
                    break

            # Extract level if available
            if 'Level' in group.columns:
                levels = group['Level'].dropna().unique()
                item.level = ', '.join(str(l) for l in levels)

            quantities.append(item)

        return quantities

    def extract_by_level(
        self,
        df: pd.DataFrame,
        group_by: str = "Type Name"
    ) -> Dict[str, List[QuantityItem]]:
        """Extract quantities grouped by level"""

        result = {}

        if 'Level' not in df.columns:
            result['All Levels'] = self.extract_quantities(df, group_by)
            return result

        for level, level_df in df.groupby('Level'):
            level_name = str(level) if pd.notna(level) else 'Unassigned'
            result[level_name] = self.extract_quantities(level_df, group_by)

        return result

    def calculate_concrete_quantities(self, df: pd.DataFrame) -> dict:
        """Calculate concrete quantities for typical elements"""

        concrete_categories = [
            'Floors', 'Stru