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
pythonimport 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
python# Load CWICR data cwicr = pd.read_parquet("TR_workitems_costs_resources_DDC_CWICR.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
pythonmaterials = [ {'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
pythoncutting = 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
pythoncustom_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
