CWICR Takeoff Helper
Business Case
Problem Statement
Quantity takeoff requires:
- Accurate calculations from dimensions
- Correct unit conversions
- Waste factor application
- Complete scope coverage
Solution
Assist takeoff process with CWICR-based calculations, automatic waste factors, unit conversions, and related item suggestions.
Business Value
- Accuracy - Validated calculations
- Completeness - Related items suggested
- Speed - Quick quantity calculations
- Consistency - Standard approaches
Technical Implementation
import pandas as pd
import numpy as np
from typing import Dict, Any, List, Optional, Tuple
from dataclasses import dataclass
from enum import Enum
import math
class TakeoffType(Enum):
"""Types of takeoff calculations."""
LINEAR = "linear" # Length
AREA = "area" # Square measure
VOLUME = "volume" # Cubic measure
COUNT = "count" # Each/number
WEIGHT = "weight" # By weight
class UnitSystem(Enum):
"""Unit systems."""
METRIC = "metric"
IMPERIAL = "imperial"
@dataclass
class TakeoffItem:
"""Single takeoff item."""
work_item_code: str
description: str
takeoff_type: TakeoffType
gross_quantity: float
waste_factor: float
net_quantity: float
unit: str
dimensions: Dict[str, float]
calculation: str
@dataclass
class TakeoffResult:
"""Complete takeoff result."""
items: List[TakeoffItem]
total_items: int
related_suggestions: List[str]
# Unit conversion factors
CONVERSIONS = {
# Length
('m', 'ft'): 3.28084,
('ft', 'm'): 0.3048,
('m', 'in'): 39.3701,
('in', 'm'): 0.0254,
# Area
('m2', 'sf'): 10.7639,
('sf', 'm2'): 0.0929,
# Volume
('m3', 'cf'): 35.3147,
('cf', 'm3'): 0.0283,
('m3', 'cy'): 1.30795,
('cy', 'm3'): 0.7646,
# Weight
('kg', 'lb'): 2.20462,
('lb', 'kg'): 0.453592,
('ton', 'kg'): 1000,
('kg', 'ton'): 0.001
}
# Standard waste factors
WASTE_FACTORS = {
'concrete': 0.05,
'rebar': 0.08,
'formwork': 0.10,
'brick': 0.10,
'block': 0.08,
'drywall': 0.12,
'tile': 0.15,
'lumber': 0.12,
'roofing': 0.10,
'paint': 0.10,
'pipe': 0.05,
'wire': 0.05,
'duct': 0.08,
'default': 0.05
}
# Related work items by category
RELATED_ITEMS = {
'concrete': ['formwork', 'rebar', 'curing', 'finishing'],
'masonry': ['mortar', 'reinforcement', 'ties', 'lintels'],
'drywall': ['framing', 'insulation', 'taping', 'painting'],
'roofing': ['underlayment', 'flashing', 'ventilation', 'insulation'],
'flooring': ['underlayment', 'adhesive', 'trim', 'transitions']
}
class CWICRTakeoffHelper:
"""Assist with quantity takeoff using CWICR data."""
def __init__(self, cwicr_data: pd.DataFrame = None):
self.cwicr = cwicr_data
if cwicr_data is not None:
self._index_cwicr()
def _index_cwicr(self):
"""Index CWICR data."""
if 'work_item_code' in self.cwicr.columns:
self._cwicr_index = self.cwicr.set_index('work_item_code')
else:
self._cwicr_index = None
def convert_unit(self, value: float, from_unit: str, to_unit: str) -> float:
"""Convert between units."""
if from_unit == to_unit:
return value
key = (from_unit.lower(), to_unit.lower())
if key in CONVERSIONS:
return value * CONVERSIONS[key]
# Try reverse
reverse_key = (to_unit.lower(), from_unit.lower())
if reverse_key in CONVERSIONS:
return value / CONVERSIONS[reverse_key]
return value
def get_waste_factor(self, work_item_code: str) -> float:
"""Get waste factor for work item."""
code_lower = work_item_code.lower()
for material, factor in WASTE_FACTORS.items():
if material in code_lower:
return factor
return WASTE_FACTORS['default']
def calculate_area(self,
length: float,
width: float,
deductions: List[Tuple[float, float]] = None) -> Dict[str, float]:
"""Calculate area with deductions."""
gross_area = length * width
deduction_area = 0
if deductions:
for d_length, d_width in deductions:
deduction_area += d_length * d_width
net_area = gross_area - deduction_area
return {
'gross_area': round(gross_area, 2),
'deductions': round(deduction_area, 2),
'net_area': round(net_area, 2),
'calculation': f"{length} x {width} = {gross_area}, minus {deduction_area} deductions"
}
def calculate_volume(self,
length: float,
width: float,
depth: float) -> Dict[str, float]:
"""Calculate volume."""
volume = length * width * depth
return {
'volume': round(volume, 3),
'calculation': f"{length} x {width} x {depth} = {volume}"
}
def calculate_perimeter(self,
length: float,
width: float) -> Dict[str, float]:
"""Calculate perimeter."""
perimeter = 2 * (length + width)
return {
'perimeter': round(perimeter, 2),
'calculation': f"2 x ({length} + {width}) = {perimeter}"
}
def calculate_concrete(self,
length: float,
width: float,
thickness: float,
work_item_code: str = "CONC-001") -> TakeoffItem:
"""Calculate concrete quantity with related items."""
volume = length * width * thickness
waste = self.get_waste_factor(work_item_code)
net_qty = volume * (1 + waste)
return TakeoffItem(
work_item_code=work_item_code,
description="Concrete",
takeoff_type=TakeoffType.VOLUME,
gross_quantity=round(volume, 3),
waste_factor=waste,
net_quantity=round(net_qty, 3),
unit="m3",
dimensions={'length': length, 'width': width, 'thickness': thickness},
calculation=f"{length}m x {width}m x {thickness}m = {volume:.3f} m3 + {waste:.0%} waste"
)
def calculate_wall_area(self,
perimeter: float,
height: float,
openings: List[Tuple[float, float]] = None,
work_item_code: str = "WALL-001") -> TakeoffItem:
"""Calculate wall area with openings deducted."""
gross_area = perimeter * height
opening_area = 0
if openings:
for w, h in openings:
opening_area += w * h
net_area = gross_area - opening_area
waste = self.get_waste_factor(work_item_code)
order_qty = net_area * (1 + waste)
return TakeoffItem(
work_item_code=work_item_code,
description="Wall finish",
takeoff_type=TakeoffType.AREA,
gross_quantity=round(gross_area, 2),
waste_factor=waste,
net_quantity=round(order_qty, 2),
unit="m2",
dimensions={'perimeter': perimeter, 'height': height, 'openings': len(openings or [])},
calculation=f"{perimeter}m x {height}m = {gross_area:.2f} m2 - {opening_area:.2f} openings + {waste:.0%} waste"
)
def calculate_flooring(self,
length: float,
width: float,
work_item_code: str = "FLOOR-001") -> TakeoffItem:
"""Calculate flooring quantity."""
area = length * width
waste = self.get_waste_factor(work_item_code)
order_qty = area * (1 + waste)
return TakeoffItem(
work_item_code=work_item_code,
description="Flooring",
takeoff_type=TakeoffType.AREA,
gross_quantity=round(area, 2),
waste_factor=waste,
net_quantity=round(order_qty, 2),
unit="m2",
dimensions={'length': length, 'width': width},
calculation=f"{length}m x {width}m = {area:.2f} m2 + {waste:.0%} waste"
)
def calculate_rebar(self,
concrete_volume: float,
kg_per_m3: float = 100,
work_item_code: str = "REBAR-001") -> TakeoffItem:
"""Calculate rebar from concrete volume."""
weight = concrete_volume * kg_per_m3
waste = self.get_waste_factor(work_item_code)
order_qty = weight * (1 + waste)
return TakeoffItem(
work_item_code=work_item_code,
description="Reinforcement",
takeoff_type=TakeoffType.WEIGHT,
gross_quantity=round(weight, 1),
waste_factor=waste,
net_quantity=round(order_qty, 1),
unit="kg",
dimensions={'concrete_m3': concrete_volume, 'kg_per_m3': kg_per_m3},
calculation=f"{concrete_volume} m3 x {kg_per_m3} kg/m3 = {weight:.1f} kg + {waste:.0%} waste"
)
def suggest_related_items(self, work_item_code: str) -> List[str]:
"""Suggest related work items."""
code_lower = work_item_code.lower()
for category, related in RELATED_ITEMS.items():
if category in code_lower:
return related
return []
def room_takeoff(self,
length: float,
width: float,
height: float,
openings: List[Tuple[float, float]] = None) -> TakeoffResult:
"""Complete room takeoff."""
items = []
# Floor
floor = self.calculate_flooring(length, width, "FLOOR-001")
items.append(floor)
# Ceiling (same as floor)
ceiling = TakeoffItem(
work_item_code="CEIL-001",
description="Ceiling",
takeoff_type=TakeoffType.AREA,
gross_quantity=floor.gross_quantity,
waste_factor=floor.waste_factor,
net_quantity=floor.net_quantity,
unit="m2",
dimensions=floor.dimensions,
calculation=f"Same as floor: {floor.gross_quantity} m2"
)
items.append(ceiling)
# Walls
perimeter = 2 * (length + width)
walls = self.calculate_wall_area(perimeter, height, openings, "WALL-001")
items.append(walls)
# Related suggestions
suggestions = ['paint', 'baseboard', 'trim', 'electrical outlets']
return TakeoffResult(
items=items,
total_items=len(items),
related_suggestions=suggestions
)
def export_takeoff(self,
items: List[TakeoffItem],
output_path: str) -> str:
"""Export takeoff to Excel."""
with pd.ExcelWriter(output_path, engine='openpyxl') as writer:
df = pd.DataFrame([
{
'Work Item Code': item.work_item_code,
'Description': item.description,
'Type': item.takeoff_type.value,
'Gross Qty': item.gross_quantity,
'Waste %': f"{item.waste_factor:.0%}",
'Net Qty': item.net_quantity,
'Unit': item.unit,
'Calculation': item.calculation
}
for item in items
])
df.to_excel(writer, sheet_name='Takeoff', index=False)
return output_pathQuick Start
# Initialize helper
helper = CWICRTakeoffHelper()
# Calculate concrete slab
concrete = helper.calculate_concrete(
length=10,
width=8,
thickness=0.2
)
print(f"Gross: {concrete.gross_quantity} m3")
print(f"Order Qty: {concrete.net_quantity} m3")
print(f"Calculation: {concrete.calculation}")Common Use Cases
1. Room Takeoff
room = helper.room_takeoff(
length=5,
width=4,
height=2.8,
openings=[(0.9, 2.1), (1.2, 1.5)] # door, window
)
for item in room.items:
print(f"{item.description}: {item.net_quantity} {item.unit}")2. Unit Conversion
meters = helper.convert_unit(100, 'ft', 'm')
print(f"100 ft = {meters:.2f} m")3. Rebar from Concrete
concrete = helper.calculate_concrete(10, 8, 0.3)
rebar = helper.calculate_rebar(concrete.gross_quantity, kg_per_m3=120)
print(f"Rebar: {rebar.net_quantity} kg")4. Related Items
related = helper.suggest_related_items("CONC-SLAB-001")
print(f"Related: {related}")Resources
- GitHub: OpenConstructionEstimate-DDC-CWICR
- DDC Book: Chapter 3.1 - Quantity Takeoff Methods