CWICR Waste Calculator

Business Case

Problem Statement

Material estimates need waste factors:

• Cutting/trimming losses
• Spillage and breakage
• Overordering requirements
• Different waste by material type

Solution

Systematic waste calculation using CWICR material data with industry-standard waste factors by material category.

Business Value

• Accurate ordering - Include realistic waste
• Cost control - Budget for actual usage
• Sustainability - Track and reduce waste
• Benchmarking - Compare waste across projects

Technical Implementation

import pandas as pd
import numpy as np
from typing import Dict, Any, List, Optional
from dataclasses import dataclass
from enum import Enum


class WasteCategory(Enum):
    """Waste category types."""
    CUTTING = "cutting"          # Cutting/trimming losses
    SPILLAGE = "spillage"        # Liquid material spillage
    BREAKAGE = "breakage"        # Damaged materials
    OVERRUN = "overrun"          # Installation overrun
    THEFT = "theft"              # Site theft allowance
    WEATHER = "weather"          # Weather damage


@dataclass
class WasteFactor:
    """Waste factor for a material."""
    material_code: str
    material_name: str
    base_quantity: float
    unit: str
    cutting_waste_pct: float
    spillage_pct: float
    breakage_pct: float
    overrun_pct: float
    total_waste_pct: float
    quantity_with_waste: float
    waste_quantity: float
    waste_cost: float


# Industry standard waste factors by material type
WASTE_FACTORS = {
    'concrete': {
        'cutting': 0.02, 'spillage': 0.03, 'breakage': 0.0, 'overrun': 0.02
    },
    'rebar': {
        'cutting': 0.05, 'spillage': 0.0, 'breakage': 0.01, 'overrun': 0.02
    },
    'brick': {
        'cutting': 0.05, 'spillage': 0.0, 'breakage': 0.03, 'overrun': 0.02
    },
    'block': {
        'cutting': 0.04, 'spillage': 0.0, 'breakage': 0.02, 'overrun': 0.02
    },
    'lumber': {
        'cutting': 0.10, 'spillage': 0.0, 'breakage': 0.02, 'overrun': 0.03
    },
    'plywood': {
        'cutting': 0.12, 'spillage': 0.0, 'breakage': 0.02, 'overrun': 0.02
    },
    'drywall': {
        'cutting': 0.10, 'spillage': 0.0, 'breakage': 0.03, 'overrun': 0.02
    },
    'tile': {
        'cutting': 0.10, 'spillage': 0.0, 'breakage': 0.05, 'overrun': 0.03
    },
    'paint': {
        'cutting': 0.0, 'spillage': 0.05, 'breakage': 0.0, 'overrun': 0.10
    },
    'mortar': {
        'cutting': 0.0, 'spillage': 0.05, 'breakage': 0.0, 'overrun': 0.03
    },
    'insulation': {
        'cutting': 0.08, 'spillage': 0.0, 'breakage': 0.02, 'overrun': 0.03
    },
    'roofing': {
        'cutting': 0.10, 'spillage': 0.0, 'breakage': 0.02, 'overrun': 0.05
    },
    'pipe': {
        'cutting': 0.05, 'spillage': 0.0, 'breakage': 0.01, 'overrun': 0.02
    },
    'wire': {
        'cutting': 0.03, 'spillage': 0.0, 'breakage': 0.0, 'overrun': 0.05
    },
    'conduit': {
        'cutting': 0.05, 'spillage': 0.0, 'breakage': 0.01, 'overrun': 0.02
    },
    'duct': {
        'cutting': 0.08, 'spillage': 0.0, 'breakage': 0.01, 'overrun': 0.03
    },
    'steel': {
        'cutting': 0.03, 'spillage': 0.0, 'breakage': 0.0, 'overrun': 0.02
    },
    'glass': {
        'cutting': 0.05, 'spillage': 0.0, 'breakage': 0.05, 'overrun': 0.02
    },
    'flooring': {
        'cutting': 0.10, 'spillage': 0.0, 'breakage': 0.02, 'overrun': 0.03
    },
    'adhesive': {
        'cutting': 0.0, 'spillage': 0.08, 'breakage': 0.0, 'overrun': 0.05
    },
    'default': {
        'cutting': 0.05, 'spillage': 0.02, 'breakage': 0.02, 'overrun': 0.03
    }
}


class CWICRWasteCalculator:
    """Calculate material waste using CWICR data."""

    def __init__(self, cwicr_data: pd.DataFrame):
        self.materials = cwicr_data
        self._index_data()

    def _index_data(self):
        """Index materials data."""
        if 'material_code' in self.materials.columns:
            self._mat_index = self.materials.set_index('material_code')
        elif 'work_item_code' in self.materials.columns:
            self._mat_index = self.materials.set_index('work_item_code')
        else:
            self._mat_index = None

    def _detect_material_type(self, description: str) -> str:
        """Detect material type from description."""
        desc_lower = str(description).lower()

        for mat_type in WASTE_FACTORS.keys():
            if mat_type in desc_lower:
                return mat_type

        # Check common synonyms
        synonyms = {
            'concrete': ['beton', 'cement'],
            'rebar': ['reinforcement', 'armature', 'арматура'],
            'brick': ['кирпич', 'block'],
            'lumber': ['wood', 'timber', 'древесина'],
            'drywall': ['gypsum', 'plasterboard', 'гипсокартон'],
            'tile': ['ceramic', 'плитка', 'керамика'],
            'paint': ['краска', 'coating'],
            'insulation': ['изоляция', 'утеплитель'],
            'pipe': ['труба', 'piping'],
            'wire': ['провод', 'cable', 'кабель']
        }

        for mat_type, words in synonyms.items():
            if any(word in desc_lower for word in words):
                return mat_type

        return 'default'

    def get_waste_factors(self, material_type: str) -> Dict[str, float]:
        """Get waste factors for material type."""
        return WASTE_FACTORS.get(material_type, WASTE_FACTORS['default'])

    def calculate_waste(self,
                        material_code: str,
                        base_quantity: float,
                        unit_cost: float = 0,
                        custom_factors: Dict[str, float] = None) -> WasteFactor:
        """Calculate waste for a material."""

        # Get material info
        material_name = material_code
        unit = "unit"

        if self._mat_index is not None and material_code in self._mat_index.index:
            mat = self._mat_index.loc[material_code]
            material_name = str(mat.get('description', mat.get('material_description', material_code)))
            unit = str(mat.get('unit', mat.get('material_unit', 'unit')))
            if unit_cost == 0:
                unit_cost = float(mat.get('material_cost', mat.get('unit_cost', 0)) or 0)

        # Detect material type and get factors
        mat_type = self._detect_material_type(material_name)
        factors = custom_factors or self.get_waste_factors(mat_type)

        cutting = factors.get('cutting', 0)
        spillage = factors.get('spillage', 0)
        breakage = factors.get('breakage', 0)
        overrun = factors.get('overrun', 0)

        # Calculate total waste
        total_waste_pct = cutting + spillage + breakage + overrun
        waste_quantity = base_quantity * total_waste_pct
        quantity_with_waste = base_quantity + waste_quantity
        waste_cost = waste_quantity * unit_cost

        return WasteFactor(
            material_code=material_code,
            material_name=material_name,
            base_quantity=base_quantity,
            unit=unit,
            cutting_waste_pct=round(cutting * 100, 1),
            spillage_pct=round(spillage * 100, 1),
            breakage_pct=round(breakage * 100, 1),
            overrun_pct=round(overrun * 100, 1),
            total_waste_pct=round(total_waste_pct * 100, 1),
            quantity_with_waste=round(quantity_with_waste, 2),
            waste_quantity=round(waste_quantity, 2),
            waste_cost=round(waste_cost, 2)
        )

    def calculate_project_waste(self,
                                 materials: List[Dict[str, Any]]) -> Dict[str, Any]:
        """Calculate waste for entire project."""

        results = []
        total_base_cost = 0
        total_waste_cost = 0

        for mat in materials:
            code = mat.get('material_code', mat.get('code'))
            qty = mat.get('quantity', 0)
            cost = mat.get('unit_cost', 0)
            custom = mat.get('waste_factors')

            waste = self.calculate_waste(code, qty, cost, custom)
            results.append(waste)

            total_base_cost += qty * cost
            total_waste_cost += waste.waste_cost

        # Summary by waste category
        by_category = {
            'cutting': sum(r.cutting_waste_pct * r.base_quantity / 100 for r in results),
            'spillage': sum(r.spillage_pct * r.base_quantity / 100 for r in results),
            'breakage': sum(r.breakage_pct * r.base_quantity / 100 for r in results),
            'overrun': sum(r.overrun_pct * r.base_quantity / 100 for r in results)
        }

        return {
            'materials': results,
            'total_base_cost': round(total_base_cost, 2),
            'total_waste_cost': round(total_waste_cost, 2),
            'waste_percentage': round(total_waste_cost / total_base_cost * 100, 1) if total_base_cost > 0 else 0,
            'by_category': by_category,
            'order_quantity_increase': round(sum(r.waste_quantity for r in results), 2)
        }

    def optimize_cutting(self,
                          material_code: str,
                          required_lengths: List[float],
                          stock_length: float) -> Dict[str, Any]:
        """Optimize cutting to minimize waste (1D cutting stock problem)."""

        # Simple first-fit decreasing algorithm
        sorted_lengths = sorted(required_lengths, reverse=True)
        stock_pieces = []
        waste_per_piece = []

        for length in sorted_lengths:
            placed = False
            for i, remaining in enumerate(stock_pieces):
                if remaining >= length:
                    stock_pieces[i] -= length
                    placed = True
                    break

            if not placed:
                stock_pieces.append(stock_length - length)

        total_stock_needed = len(stock_pieces)
        total_material = total_stock_needed * stock_length
        total_used = sum(required_lengths)
        total_waste = total_material - total_used
        waste_pct = total_waste / total_material * 100 if total_material > 0 else 0

        return {
            'material_code': material_code,
            'stock_pieces_needed': total_stock_needed,
            'stock_length': stock_length,
            'total_material': round(total_material, 2),
            'total_used': round(total_used, 2),
            'total_waste': round(total_waste, 2),
            'waste_percentage': round(waste_pct, 1),
            'cutting_efficiency': round(100 - waste_pct, 1)
        }

    def export_waste_report(self,
                            project_waste: Dict[str, Any],
                            output_path: str) -> str:
        """Export waste report to Excel."""

        with pd.ExcelWriter(output_path, engine='openpyxl') as writer:
            # Summary
            summary_df = pd.DataFrame([{
                'Total Base Cost': project_waste['total_base_cost'],
                'Total Waste Cost': project_waste['total_waste_cost'],
                'Waste Percentage': project_waste['waste_percentage'],
                'Order Increase': project_waste['order_quantity_increase']
            }])
            summary_df.to_excel(writer, sheet_name='Summary', index=False)

            # Materials
            mat_df = pd.DataFrame([
                {
                    'Material': m.material_name,
                    'Base Qty': m.base_quantity,
                    'Unit': m.unit,
                    'Cutting %': m.cutting_waste_pct,
                    'Spillage %': m.spillage_pct,
                    'Breakage %': m.breakage_pct,
                    'Overrun %': m.overrun_pct,
                    'Total Waste %': m.total_waste_pct,
                    'Order Qty': m.quantity_with_waste,
                    'Waste Cost': m.waste_cost
                }
                for m in project_waste['materials']
            ])
            mat_df.to_excel(writer, sheet_name='Materials', index=False)

        return output_path

Quick Start

# Load CWICR data
cwicr = pd.read_parquet("ddc_cwicr_en.parquet")

# Initialize calculator
waste_calc = CWICRWasteCalculator(cwicr)

# Calculate waste for single material
waste = waste_calc.calculate_waste(
    material_code="CONC-001",
    base_quantity=100,
    unit_cost=150
)

print(f"Base Qty: {waste.base_quantity}")
print(f"Order Qty: {waste.quantity_with_waste}")
print(f"Waste: {waste.total_waste_pct}%")
print(f"Waste Cost: ${waste.waste_cost:,.2f}")

Common Use Cases

1. Project-Wide Waste

materials = [
    {'code': 'CONC-001', 'quantity': 200, 'unit_cost': 150},
    {'code': 'REBAR-002', 'quantity': 5000, 'unit_cost': 1.2},
    {'code': 'BRICK-003', 'quantity': 10000, 'unit_cost': 0.50}
]

project = waste_calc.calculate_project_waste(materials)
print(f"Total Waste Cost: ${project['total_waste_cost']:,.2f}")

2. Cutting Optimization

cutting = waste_calc.optimize_cutting(
    material_code="REBAR-001",
    required_lengths=[2.5, 3.0, 1.8, 2.2, 4.0, 3.5],
    stock_length=6.0
)
print(f"Efficiency: {cutting['cutting_efficiency']}%")

3. Custom Waste Factors

custom_factors = {'cutting': 0.15, 'spillage': 0, 'breakage': 0.05, 'overrun': 0.05}
waste = waste_calc.calculate_waste("TILE-001", 500, 25, custom_factors)

Resources

• GitHub: OpenConstructionEstimate-DDC-CWICR
• DDC Book: Chapter 3.1 - Material Waste Management