afrexai-construction-estimator（Afrexai 施工估算器）

Construction Estimator Pro

Complete construction estimating methodology — from quantity takeoff to bid submission. Zero dependencies.

Phase 1: Project Classification & Estimate Type

Estimate Type Decision Matrix

Project Brief YAML

project:
  name: ""
  number: ""
  type: residential | commercial | industrial | infrastructure | renovation
  delivery: design-bid-build | design-build | CM-at-risk | IPD
  location:
    city: ""
    state: ""
    zip: ""
    location_factor: 1.00  # RSMeans city cost index / national average
  owner: ""
  architect: ""
  
scope:
  gross_sf: 0
  stories: 0
  site_acres: 0
  description: ""
  
schedule:
  bid_date: ""
  construction_start: ""
  substantial_completion: ""
  duration_months: 0
  
estimate:
  type: order-of-magnitude | conceptual | detailed | definitive
  base_date: ""  # Date costs are based on
  escalation_rate: 0.04  # Annual construction cost escalation
  
assumptions:
  - ""
exclusions:
  - ""
allowances:
  - item: ""
    amount: 0

Project Type Quick Reference

Phase 2: Quantity Takeoff (QTO)

CSI MasterFormat Division Structure

Use CSI MasterFormat 2018 for ALL estimates. Every line item maps to a division.

QTO Best Practices

1. Measure twice, price once — QTO errors cascade through the entire estimate
2. Use consistent units — SF for areas, LF for linear, CY for volume, EA for items
3. Add waste factors by material:

- Concrete: 5-8% - Masonry: 3-5% - Drywall: 10-12% - Roofing: 8-10% - Flooring (tile): 10-15% - Lumber: 8-10% - Rebar: 5-7% - Paint: 10-15%

1. Document measurement methodology — so anyone can verify
2. Cross-check totals — SF of drywall ≈ 2.5-3x floor area (both sides of walls + ceilings)

QTO Line Item Template

line_item:
  division: "03"
  spec_section: "03 30 00"
  description: "Cast-in-Place Concrete - Elevated Slabs"
  quantity: 450
  unit: CY
  unit_cost:
    labor: 85.00
    material: 165.00
    equipment: 25.00
    subcontractor: 0.00
  total_unit_cost: 275.00
  extended_cost: 123750.00
  waste_factor: 0.07
  adjusted_quantity: 481.5
  notes: "4500 PSI, #5 rebar @ 12\" OC EW, 6\" slab"
  source: "Sub quote - ABC Concrete (02/15/2026)"
  confidence: high | medium | low

Quantity Verification Cross-Checks

Phase 3: Pricing & Cost Assembly

Unit Cost Development

Cost source hierarchy (most reliable first):

1. Subcontractor quotes (3 minimum per trade) — best for bid estimates
2. Historical project data — adjusted for location, time, scope
3. RSMeans/Gordian data — industry standard reference
4. Vendor quotes — for specific materials/equipment
5. Published cost guides — Marshall & Swift, Craftsman

Labor Cost Build-Up

labor_rate_build_up:
  trade: "Carpenter"
  base_wage: 42.50
  fringe_benefits: 18.75   # Health, pension, vacation, training
  payroll_taxes: 8.90      # FICA, FUTA, SUTA, workers comp
  total_burden: 27.65
  burdened_rate: 70.15
  
  productivity_factors:
    weather: 1.00           # 1.0 = normal, 1.15 = winter
    overtime: 1.00          # 1.0 = straight time, 1.5 = OT
    height: 1.00            # 1.0 = ground, 1.10 = >30ft
    congestion: 1.00        # 1.0 = open, 1.15 = tight
    shift: 1.00             # 1.0 = day, 1.10 = swing, 1.15 = night
  adjusted_rate: 70.15

Subcontractor Quote Evaluation

Score each sub quote (use minimum 3 per trade):

Red flags in sub quotes:

• "As needed" or "TBD" line items (scope gap)
• Short validity period (<30 days)
• Unusual exclusions (e.g., electrician excluding wire)
• No reference to spec sections
• Price significantly below others (they missed something)

Crew Rate Assembly

Crew Daily Cost = Σ(Workers × Daily Rate) + Equipment Daily Cost
Crew Daily Output = Units per 8-hour day (from labor standards)
Unit Cost = Crew Daily Cost ÷ Crew Daily Output

Example — Concrete Placement Crew:

• 1 Foreman @ $75/hr × 8 = $600
• 4 Laborers @ $55/hr × 8 = $1,760
• 1 Vibrator operator @ $60/hr × 8 = $480
• Concrete pump (daily rental) = $1,200
• Crew Daily Cost = $4,040
• Daily output: 50 CY
• Unit Labor+Equipment Cost = $80.80/CY
• Material (concrete delivered) = $165/CY
• Total in-place cost = $245.80/CY

Phase 4: Indirect Costs & Markups

General Conditions (Division 01) Checklist

Rule of thumb: General conditions = 8-15% of direct costs (lower for large projects, higher for small/complex).

Markup Stack

markup_calculation:
  direct_costs: 2500000
  
  general_conditions:
    percentage: 0.10
    amount: 250000
    
  subtotal_1: 2750000
  
  overhead:
    percentage: 0.05     # Home office overhead
    amount: 137500
    
  subtotal_2: 2887500
  
  profit:
    percentage: 0.05     # Varies by market/risk
    amount: 144375
    
  subtotal_3: 3031875
  
  contingency:
    design_contingency: 0.05    # For incomplete drawings
    construction_contingency: 0.03  # For unforeseen conditions
    amount: 242550
    
  bond:
    percentage: 0.015
    amount: 49118
    
  escalation:
    rate: 0.04           # Annual
    months_to_midpoint: 8
    amount: 88536
    
  total_estimate: 3412079
  cost_per_sf: 341.21    # For 10,000 SF building

Contingency Guide

Contingency is NOT profit padding. Track and justify every contingency draw.

Phase 5: Bid Preparation & Strategy

Bid/No-Bid Decision Scorecard

Score 1-5 for each (minimum 30 to bid):

Bid Day Checklist

48 hours before:

• [ ] All sub quotes received (minimum 3 per trade)
• [ ] All material quotes current (check expiration dates)
• [ ] Addenda reviewed and incorporated (ALL of them)
• [ ] Scope gaps identified and plugged
• [ ] Math verified (independent check)

Day of bid:

• [ ] Final sub quotes plugged in
• [ ] Markup/profit decision finalized
• [ ] Alternates priced if required
• [ ] Unit prices calculated if required
• [ ] Bid bond secured
• [ ] Bid form completed correctly (every blank filled)
• [ ] Acknowledge ALL addenda on bid form
• [ ] Authorized signature
• [ ] Delivered before deadline (allow 1+ hour buffer)

Competitive Bid Strategy

Market conditions affect markup:

• Hot market (lots of work): Markup 8-12% (O&P combined)
• Normal market: Markup 6-10%
• Slow market: Markup 3-6%
• Must-win/strategic: Markup 2-4% (minimum to cover overhead)

Bid spread analysis (track your results):

Bid Spread = (Your Bid - Low Bid) ÷ Low Bid × 100

• Consistently >10% high → Your costs are inflated or productivity assumptions too conservative
• Consistently <2% from low → You might be leaving money on the table
• Target: Within 3-5% of winning bid

Phase 6: Value Engineering (VE)

VE Opportunity Matrix

VE Proposal Template

ve_item:
  number: VE-001
  description: "Substitute VRF system for conventional VAV"
  division: "23"
  
  original:
    description: "VAV air handling system with ductwork"
    cost: 850000
    
  proposed:
    description: "Variable Refrigerant Flow (VRF) with DOAS"
    cost: 680000
    
  savings: 170000
  savings_pct: 20%
  
  impact:
    schedule: "Reduces mechanical rough-in by 2 weeks"
    quality: "Better zone control, lower operating cost"
    maintenance: "Higher per-unit cost but less ductwork"
    code_compliance: "Meets ASHRAE 90.1, verify local amendments"
    
  risk: medium
  recommendation: accept | reject | modify
  requires_redesign: yes | no
  redesign_cost: 15000
  net_savings: 155000

VE Decision Rules

1. Never VE life safety — fire protection, structural integrity, egress
2. Calculate lifecycle cost — cheap upfront ≠ cheap over 20 years
3. Get architect/engineer sign-off before bidding VE alternates
4. Document everything — VE that isn't documented becomes a scope gap
5. Owner decides — present options with data, let them choose

Phase 7: Change Order Management

Change Order Pricing Rules

Contractor markup on changes (typical):

Time & Material (T&M) documentation requirements:

• Daily time sheets signed by owner's rep
• Material invoices with delivery tickets
• Equipment logs with hours
• Photos of work in progress

Change Order YAML Template

change_order:
  number: CO-001
  date: ""
  description: ""
  
  reason:
    type: owner-directed | unforeseen-condition | design-error | code-change | scope-clarification
    rfi_number: ""
    
  cost_breakdown:
    labor:
      hours: 0
      rate: 0
      total: 0
    material:
      items: []
      total: 0
    equipment:
      items: []
      total: 0
    subcontractor:
      items: []
      total: 0
    direct_cost: 0
    markup: 0.15
    total_cost: 0
    
  schedule_impact:
    days: 0
    critical_path: yes | no
    explanation: ""
    
  status: pending | approved | rejected | negotiating

Change Order Negotiation Tips

1. Price it immediately — delay weakens your position
2. Submit with backup — labor rates, material quotes, productivity analysis
3. Separate time from money — negotiate schedule impact independently
4. Track cumulative impact — 20 small changes = major schedule disruption (even if each is "0 days")
5. Constructive acceleration — if owner delays approval but expects same completion, document it
6. Unit price book — agree on unit prices at contract start for common change types

Phase 8: Cost Control During Construction

Earned Value Management (EVM)

Budget at Completion (BAC) = Total budget
Planned Value (PV) = Budgeted cost of work scheduled
Earned Value (EV) = Budgeted cost of work performed
Actual Cost (AC) = Actual cost of work performed

Schedule Performance Index (SPI) = EV / PV
  >1.0 = ahead of schedule
  <1.0 = behind schedule

Cost Performance Index (CPI) = EV / AC
  >1.0 = under budget
  <1.0 = over budget

Estimate at Completion (EAC) = BAC / CPI
Variance at Completion (VAC) = BAC - EAC

Monthly Cost Report Template

cost_report:
  project: ""
  period: ""
  report_date: ""
  
  summary:
    original_contract: 0
    approved_changes: 0
    pending_changes: 0
    current_budget: 0
    committed_cost: 0      # Subcontracts + POs
    actual_cost_to_date: 0
    forecast_to_complete: 0
    estimate_at_completion: 0
    variance: 0
    contingency_remaining: 0
    
  schedule:
    percent_complete: 0
    spi: 0
    cpi: 0
    days_ahead_behind: 0
    
  cash_flow:
    billed_to_date: 0
    collected_to_date: 0
    retention_held: 0
    
  risk_items:
    - description: ""
      potential_cost: 0
      probability: high | medium | low
      mitigation: ""

Cost Control Red Flags

Phase 9: Specialty Estimate Types

Renovation/Remodel Estimating

Add these factors to renovation estimates:

• Selective demolition: Price item-by-item (never lump sum)
• Hazmat survey: Asbestos ($3-5K), lead paint ($2-4K) — MANDATORY before bid
• Abatement: 2-5x removal cost vs new construction equivalent
• Protection of existing: Dust barriers, floor protection, HVAC isolation
• Working hours: Occupied buildings = nights/weekends = premium labor
• Discovery allowance: 10-15% for hidden conditions behind walls
• Temporary facilities: HVAC, power, restrooms during renovation
• Phasing/sequencing: Adds 15-30% management overhead

Sitework Estimating

Critical factors:

sitework_checklist:
  geotechnical:
    - Soil bearing capacity
    - Water table depth  
    - Rock depth (blasting vs mechanical?)
    - Contamination (Phase I/II ESA results)
    
  earthwork:
    cut_cy: 0
    fill_cy: 0
    import_export: 0    # Net CY to haul
    haul_distance_miles: 0
    compaction_required: standard | proctor_95 | proctor_98
    
  utilities:
    water_tap_fee: 0
    sewer_tap_fee: 0
    fire_line: 0
    storm_detention: required | not_required
    
  paving:
    asphalt_sy: 0
    concrete_sy: 0
    curb_lf: 0
    striping_lf: 0
    
  landscape:
    sod_sf: 0
    trees_ea: 0
    irrigation: yes | no
    erosion_control: silt_fence | inlet_protection | retention_pond

MEP (Mechanical/Electrical/Plumbing) Quick Checks

Phase 10: Escalation & Location Adjustments

Construction Cost Escalation

Future Cost = Current Cost × (1 + Annual Rate) ^ (Months to Midpoint ÷ 12)

Recent escalation trends (US):

• 2020-2022: 8-15% annually (pandemic/supply chain)
• 2023-2024: 4-6% annually (normalizing)
• 2025-2026 forecast: 3-5% annually
• Long-term average: 3-4% annually

Always escalate to the MIDPOINT of construction, not the start.

Location Factor Application

Local Cost = National Average Cost × City Cost Index

Sample RSMeans City Cost Indices (100 = national average):

Phase 11: Estimate Quality Review

100-Point Estimate Quality Rubric

Grading: 90+ = Bid-ready | 75-89 = Needs refinement | 60-74 = Major gaps | <60 = Redo

Peer Review Checklist

• [ ] All addenda acknowledged and incorporated?
• [ ] Spec sections cross-referenced to QTO? (no orphan specs)
• [ ] Sub quotes match scope of work? (read exclusions!)
• [ ] General conditions duration matches schedule?
• [ ] Bond premium calculated on TOTAL including markups?
• [ ] Sales tax applied correctly? (varies by state, some exempt)
• [ ] Prevailing wage rates used if required? (Davis-Bacon, state)
• [ ] Owner-furnished items excluded from pricing?
• [ ] Alternates priced separately and clearly?
• [ ] Math checked independently? (not just formula check — spot-check quantities)

Phase 12: Common Mistakes & Edge Cases

10 Estimate-Killing Mistakes

Edge Cases

Occupied building renovation:

• Work hours restriction → labor premium 15-40%
• Dust/noise control → add $2-5/SF
• Security/escort requirements → add supervision cost
• Existing condition discovery → 10-15% allowance minimum

Remote/rural project:

• Travel/per diem for crews → $150-$250/worker/day
• Material delivery premium → 5-15% depending on distance
• Limited sub market → fewer quotes, less competitive pricing
• Equipment mobilization → long haul costs for cranes, excavators

Fast-track schedule:

• Overtime premium → plan 20-30% labor cost increase
• Acceleration costs → additional supervision, equipment
• Out-of-sequence work → productivity losses 10-25%
• Premium material delivery → expediting fees

Public/government work:

• Prevailing wages → 20-40% labor cost increase
• DBE/MBE/WBE goals → subcontracting requirements, good faith effort
• Buy American/Buy America → material cost premium 10-30%
• Bid protest risk → ensure perfect compliance with ITB

Design-Build:

• Design contingency higher (incomplete docs at pricing)
• Self-perform vs sub trade-offs
• Design liability insurance (professional liability)
• Allowances for owner decisions not yet made

Natural Language Commands