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

python
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_path

Quick Start

python
# 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

python
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

python
meters = helper.convert_unit(100, 'ft', 'm')
print(f"100 ft = {meters:.2f} m")

3. Rebar from Concrete

python
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

python
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