Cost Tracking Skill

Budgets are organized by CSI Division to align with project specifications and standard construction cost accounting:

{
  "budget": {
    "original_contract_value": 2770000,
    "approved_cos_amount": 35000,
    "current_contract_value": 2805000,
    "budget_by_division": [
      {
        "division_number": "01",
        "division_title": "General Requirements",
        "description": "Site mobilization, project management, temporary facilities",
        "original_amount": 145000,
        "applied_cos": [
          { "co_id": "CO-001", "amount": 5000 },
          { "co_id": "CO-003", "amount": -2000 }
        ],
        "current_amount": 148000,
        "committed_costs": 65000,
        "invoiced_costs": 45000,
        "paid_costs": 40500,
        "forecast_to_complete": 85000,
        "total_forecast": 130500,
        "notes": ""
      },
      {
        "division_number": "02",
        "division_title": "Existing Conditions",
        "description": "Demolition and site preparation",
        "original_amount": 85000,
        "applied_cos": [],
        "current_amount": 85000,
        "committed_costs": 78500,
        "invoiced_costs": 65000,
        "paid_costs": 58500,
        "forecast_to_complete": 12000,
        "total_forecast": 77000,
        "notes": ""
      }
    ]
  }
}

Budget Line Item Fields

Budget Initialization

When the superintendent first sets up cost tracking via /cost, initialize cost-data.json with:

Required fields:

• original_contract_value (number) — Total contract amount from the executed contract
• budget_by_division[] — Array of CSI division budget line items, each with:
  • division (string) — CSI division code (e.g., "03", "04", "05")
  • description (string) — Division name (e.g., "Concrete", "Masonry", "Metals")
  • original_amount (number) — Original budget for this division
  • current_amount (number) — Current budget (original + approved COs)
  • committed_costs (number) — Subcontract + PO amounts
  • applied_cos[] (array) — Change orders applied to this division, each referencing change-order-log.json entries
• contingency (object):
  • original_amount (number) — Starting contingency
  • current_amount (number) — Remaining after draws
  • draws[] (array) — Each draw with date, amount, description, CO reference
• allowances[] (array) — Contract allowances with original vs. spent tracking

Schedule of Values (SOV) linkage:

• Each division line item links to pay-app-log.json SOV line items via sov_line_number
• Percent complete per line feeds earned value calculations in earned-value-management
• SOV structure: sov_line_number, description, scheduled_value, work_completed_previous, work_completed_this_period, materials_presently_stored, total_completed_and_stored, percent_complete, balance_to_finish, retainage

Cost Performance Index (CPI) Calculation

The Cost Performance Index measures how efficiently the project is spending money:

CPI = Earned Value / Actual Costs

Where:
  Earned Value = Current budget × % complete
  Actual Costs = Invoiced + paid costs to date

Interpretation:

• CPI = 1.0: Spending perfectly on schedule
• CPI > 1.0: Under budget (spending less than earned)
• CPI < 1.0: Over budget (spending more than earned)

Example:

• Current Budget: $2,805,000
• Project % Complete: 12%
• Earned Value: $2,805,000 × 0.12 = $336,600
• Actual Costs: $320,000 (invoiced)
• CPI = $336,600 / $320,000 = 1.05 (5% under budget)

Cost Forecasting Methods

Method 1: Estimate at Completion (EAC) — CPI-Based

Uses current cost performance to project final cost:

EAC = Actual Costs + (Remaining Work / CPI)

Or equivalently:
EAC = Budget / CPI

Example:

• Current Budget: $2,805,000
• CPI: 1.05 (spending efficiently)
• EAC = $2,805,000 / 1.05 = $2,671,429
• Projected Savings: $133,571

Method 2: EAC — Revised Estimate

Uses fresh estimate of remaining work (accounting for known scope changes):

EAC = Actual Costs + Revised Estimate to Complete

Where:
  Revised Estimate = Original estimate − (% complete work)

Example:

• Actual Costs: $320,000
• Original remaining estimate: $2,485,000
• % Complete: 12%
• Revised remaining = $2,485,000 × (1 − 0.12) = $2,186,600
• EAC = $320,000 + $2,186,600 = $2,506,600

Method 3: Forecast by Burn Rate

Projects final cost based on average daily/weekly spending:

EAC = Actual Costs + (Daily Burn Rate × Days Remaining)

Example:

• Current Spent: $320,000
• Days Elapsed: 27
• Daily Burn Rate: $320,000 / 27 = $11,852/day
• Days Remaining: 124
• Forecast Remaining: $11,852 × 124 = $1,469,648
• EAC = $320,000 + $1,469,648 = $1,789,648

Variance Analysis

Variance tracking identifies where costs deviate from plan:

Budget Variance by Division

Budget Variance = Current Budget − Total Forecast

Or as % of Budget:
Variance % = (Budget Variance / Current Budget) × 100%

Example — Division 03 (Concrete):

• Current Budget: $190,000
• Total Forecast (invoiced + remaining): $195,000
• Variance: −$5,000 (5.3% over budget)
• Flag: Red alert when variance exceeds ±5%

Schedule Variance Impact on Costs

When a project falls behind schedule, labor and overhead costs extend:

Schedule Variance Cost = Daily overhead rate × Days behind schedule

Where:
  Daily overhead = (Division 01 budget / Total project days)

Example:

• General Requirements (overhead): $145,000
• Total project days: 151
• Daily overhead: $145,000 / 151 = $961/day
• If 10 days behind schedule:
• Schedule Variance Cost = $961 × 10 = $9,610

Material Cost Variance

Actual material costs vs. estimated:

Material Variance = (Actual Material Cost − Budgeted Material Cost)

By Line Item:
  Concrete variance = Actual spent on concrete − budgeted for concrete
  Steel variance = Actual spent on steel − budgeted for steel

Example:

• Budgeted PEMB Steel (Division 05): $85,000
• Committed through supplier POs: $88,500
• Material Variance: −$3,500 (4.1% over)

Contingency Tracking

Contingency is reserve funds to cover unforeseen conditions and changes:

{
  "contingency": {
    "original_contingency_amount": 150000,
    "contingency_percentage_of_budget": 5.4,
    "spent_against_contingency": [
      { "co_id": "CO-001", "amount": 50000, "description": "Owner-directed scope addition" },
      { "co_id": "CO-003", "amount": -15000, "description": "Value engineering credit" }
    ],
    "total_spent_from_contingency": 35000,
    "available_contingency": 115000,
    "available_contingency_percentage": 4.1,
    "drawdown_rate_per_month": 5833,
    "months_of_contingency_remaining": 19.7,
    "alert_threshold_percent": 50,
    "contingency_status": "healthy"
  }
}

Contingency Drawdown Rules:

• 0–25% drawn: Green — Healthy reserve
• 25–50% drawn: Yellow — Monitor closely
• 50–75% drawn: Orange — Review budget; may need change order to owner
• 75%+ drawn: Red — Contingency at risk

Invoice Reconciliation Process

Sub Invoice Verification Workflow

1. Receive Sub Invoice: Sub submits invoice for work/materials
2. Verify Against SOV: Check invoice amount ≤ (% complete × contract amount)
3. Cross-Reference with Pay App: Confirm line items match SOV
4. Flag Overbilling: If invoice > % complete, reject or request clarification
5. Apply Retainage: Hold back 10% (or contract rate) from payment
6. Process Payment: Pay sub after conditional lien waiver received
7. Update Cost Tracking: Record payment in cost-data.json

Overbilling Detection

Maximum billable amount = Line item contract amount × % complete

Example:
  Division 03 contract: $185,000
  Division 03 % complete: 45%
  Maximum billable: $185,000 × 0.45 = $83,250

  If invoice shows: $87,000 → FLAG OVERBILLING
  Difference: $3,750 excess
  Action: Request clarification or deny until work verified

Retainage Tracking by Sub

{
  "sub_retainage_tracking": {
    "subcontractor": "W Principles (Concrete)",
    "contract_amount": 185000,
    "invoiced_to_date": 120000,
    "retainage_rate": 0.10,
    "retainage_held": 12000,
    "amount_paid": 108000,
    "percent_complete": 65,
    "retainage_policy": "W Principles flat 10% until substantial completion",
    "retainage_released_at_substantial_completion": true,
    "notes": "Flat 10% retainage per W Principles standard"
  }
}

Project Intelligence Integration

When project intelligence is loaded, cross-reference cost data against extracted quantities, schedule progress, and procurement to identify cost risks early.

Quantity Verification

Compare budgeted quantities against plan-extracted quantities:

• Read plans-spatial.json → quantities → for each CSI division, sum the relevant quantities (concrete CY, wall SF, flooring SF, fixture counts, etc.)
• Compare against budget line items in cost-data.json → budget_by_division[]
• Calculate: Plan quantity × estimated unit rate vs budget amount
• Flag divisions where plan quantities exceed budget quantities by >5% — this indicates the estimate may have missed scope
• Example: Division 03 budget assumes 38 CY total concrete, but plans-spatial.json quantities show 42.3 CY → flag 11% overage for review

Schedule-Cost Alignment

Cross-check cost progress against schedule progress:

• Read schedule.json → percent_complete → overall project progress
• Compare with cost % complete per division: (invoiced_costs / current_amount) for each budget line
• Flag front-loading: If cost % complete significantly exceeds schedule % complete for a division, the sub may be overbilling
• Flag lagging: If cost % complete is far below schedule % complete, work may be unbilled or behind
• Example: Schedule 25% complete, Division 03 (Concrete) 40% billed → possible front-loading

Change Order Linkage

Verify change order cost impacts are properly reflected in budget:

• Read change-order-log.json → for each CO with status "approved"
• Check that the CO's cost_approved amount appears in the correct budget division's applied_cos[] array
• Flag any approved COs not yet reflected in budget divisions
• Example: CO-005 approved for $17,800 affecting Division 26 → verify Division 26 applied_cos includes CO-005

Procurement Cost Tracking

Compare committed material costs against budget line items:

• Read procurement-log.json → sum total_cost by spec section → map to CSI divisions
• Compare against budget division committed_costs
• Flag material cost overruns before they hit invoicing
• Example: Procurement for Division 05 (Steel) totals $88,500 committed, but budget shows $85,000 → flag $3,500 (4.1%) material cost overrun

Extended reference: Detailed examples, templates, scoring rubrics, and best practices are in references/skill-detail.md.