Generate photo-based construction cost estimates with GPT-4 Vision and DDC CWICR
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Overview
Upload a construction photo via web form → get a detailed cost estimate with work breakdown, resource costs, and professional HTML report. Powered by GPT-4 Vision and the open-source DDC CWICR database (55,000+ work items).
Who's it for
- Site managers who need quick estimates from mobile photos
- Renovation contractors evaluating project scope from initial site visit
- Real estate inspectors estimating repair costs
- Construction consultants providing rapid ballpark figures
- DIY enthusiasts planning home improvement budgets
What it does
- Collects photo + region/language via n8n Form
- Analyzes photo with GPT-4 Vision (room type, elements, dimensions)
- Decomposes visible elements into construction work items
- Searches DDC CWICR vector database for matching rates
- Generates professional HTML report with cost breakdown
Supports 9 regions: 🇩🇪 Berlin · 🇬🇧 Toronto · 🇷🇺 St. Petersburg · 🇪🇸 Barcelona · 🇫🇷 Paris · 🇧🇷 São Paulo · 🇨🇳 Shanghai · 🇦🇪 Dubai · 🇮🇳 Mumbai
How it works
┌──────────────┐ ┌───────────────┐ ┌───────────────┐ ┌──────────────┐
│ Web Form │ → │ STAGE 1 │ → │ STAGE 4 │ → │ Loop Works │
│ Photo+Lang │ │ GPT-4 Vision │ │ Decompose │ │ per item │
└──────────────┘ └───────────────┘ └───────────────┘ └──────────────┘
↓ ↓ ↓
┌─────────────────────────────────────────────────────┐
│ Identify room, elements, fixtures, dimensions │
│ → Break down into 15-40 construction work items │
└─────────────────────────────────────────────────────┘
↓
┌──────────────┐ ┌───────────────┐ ┌───────────────┐ ┌──────────────┐
│ HTML Report │ ← │ STAGE 7.5 │ ← │ STAGE 5 │ ← │ Qdrant │
│ Response │ │ Aggregate │ │ Parse+Score │ │ Vector DB │
└──────────────┘ └───────────────┘ └───────────────┘ └──────────────┘
Pipeline stages:
| Stage | Node | Description |
|---|---|---|
| 1 | GPT-4 Vision | Analyzes photo: room type, elements, materials, dimensions |
| 4 | GPT-4 Decompose | Breaks elements into work items with quantities |
| 5 | Vector Search + Score | Finds matching rates in DDC CWICR, quality scoring |
| 7.5 | Aggregate & Validate | Sums costs, groups by phase, validates results |
| 9 | HTML Report | Generates professional estimate document |
Prerequisites
| Component | Requirement |
|---|---|
| n8n | v1.30+ with Form Trigger support |
| OpenAI API | GPT-4 Vision + Embeddings access |
| Qdrant | Vector DB with DDC CWICR collections |
| DDC CWICR Data | github.com/datadrivenconstruction/DDC-CWICR |
Setup
1. n8n Credentials (Settings → Credentials)
- OpenAI API — required (GPT-4 Vision + text-embedding-3-large)
- Qdrant API — your Qdrant instance connection
2. Qdrant Collections
Load DDC CWICR embeddings for your target regions:
DE_BERLIN_workitems_costs_resources_EMBEDDINGS_3072_DDC_CWICR
ENG_TORONTO_workitems_costs_resources_EMBEDDINGS_3072_DDC_CWICR
RU_STPETERSBURG_workitems_costs_resources_EMBEDDINGS_3072_DDC_CWICR
ES_BARCELONA_workitems_costs_resources_EMBEDDINGS_3072_DDC_CWICR
FR_PARIS_workitems_costs_resources_EMBEDDINGS_3072_DDC_CWICR
PT_SAOPAULO_workitems_costs_resources_EMBEDDINGS_3072_DDC_CWICR
ZH_SHANGHAI_workitems_costs_resources_EMBEDDINGS_3072_DDC_CWICR
AR_DUBAI_workitems_costs_resources_EMBEDDINGS_3072_DDC_CWICR
HI_MUMBAI_workitems_costs_resources_EMBEDDINGS_3072_DDC_CWICR
3. Activate Workflow
- Import JSON into n8n
- Link OpenAI + Qdrant credentials to respective nodes
- Activate workflow
- Access form at:
https://your-n8n/form/photo-estimate-pro-v3
Features
| Feature | Description |
|---|---|
| 📸 Photo Analysis | GPT-4 Vision identifies room type, elements, fixtures |
| 📏 Dimension Estimation | Uses reference objects (doors, tiles) for sizing |
| 🔧 Work Decomposition | Breaks down to 15-40 specific work items |
| 🎯 Quality Scoring | Rates match quality (high/medium/low/not_found) |
| 📊 Phase Grouping | PREPARATION → MAIN → FINISHING → MEP |
| 💰 Cost Breakdown | Labor, materials, machines per item |
| ✅ Validation | Warns if <50% rates found or missing demolition |
| 🌍 9 Languages | Full localization + regional pricing |
Form Fields
| Field | Type | Options |
|---|---|---|
| 📷 Upload Photo | File | .jpg, .png, .webp |
| 🌍 Region & Language | Dropdown | 9 regions with currencies |
| 🏗️ Work Type | Dropdown | New / Renovation / Repair / Auto |
| 📝 Description | Textarea | Optional context |
Example Output
Input: Bathroom photo (renovation) Region: 🇩🇪 German - Berlin (EUR €)
Generated Work Items:
PREPARATION (3 items)
├── Demolition of wall tiles — 12 m2 — €180
├── Demolition of floor tiles — 4.5 m2 — €95
└── Disposal of construction waste — 0.8 m3 — €120
MAIN (8 items)
├── Floor waterproofing — 4.5 m2 — €225
├── Wall waterproofing wet zone — 8 m2 — €280
├── Floor screed — 4.5 m2 — €135
├── Wall tiling — 22 m2 — €880
├── Floor tiling — 4.5 m2 — €225
├── Toilet installation — 1 pcs — €320
├── Sink installation — 1 pcs — €185
└── Shower cabin installation — 1 pcs — €450
FINISHING (3 items)
├── Ceiling painting — 4.5 m2 — €68
├── Grouting — 26.5 m2 — €133
└── Silicone sealing — 8 m — €48
MEP (4 items)
├── Socket installation — 2 pcs — €90
├── Light point installation — 2 pcs — €120
├── Mixer/faucet installation — 2 pcs — €160
└── Ventilation installation — 1 pcs — €85
─────────────────────────────────────
TOTAL: €3,799.00
Labor: €1,520 · Materials: €1,900 · Machines: €379
Quality: 78% high match · 18 work items
Quality Scoring System
| Score | Level | Meaning |
|---|---|---|
| 60-100 | 🟢 High | Exact match with resources |
| 40-59 | 🟡 Medium | Good match, minor differences |
| 20-39 | 🟠 Low | Partial match, review needed |
| 0-19 | 🔴 Not Found | No suitable rate found |
Scoring factors:
- Has price in database (+30)
- Has resources breakdown (+25)
- Unit matches expected (+20)
- Material keywords match (+15)
- Work type keywords match (+10)
- Vector similarity >0.5 (+10)
Notes & Tips
- Best photo angles: Capture full room, include reference objects (doors, sockets)
- Renovation mode: AI automatically adds demolition works
- Validation warnings: Check if <50% rates found — may need manual additions
- Rate accuracy: Depends on DDC CWICR coverage for your region
- Extend: Chain with PDF generation, email delivery, or CRM integration
Categories
AI · Data Extraction · Document Ops · Files & Storage
Tags
photo-analysis, gpt-4-vision, construction, cost-estimation, qdrant, vector-search, form-trigger, html-report, multilingual
Author
DataDrivenConstruction.io https://DataDrivenConstruction.io [email protected]
Consulting & Training
We help construction, engineering, and technology firms implement:
- AI-powered visual estimation systems
- CAD/BIM data processing pipelines
- Vector database integration for construction data
- Multilingual cost database solutions
Contact us to test with your data or adapt to your project requirements.
Resources
- DDC CWICR Database: GitHub
- Qdrant Documentation: qdrant.tech/documentation
- n8n Form Trigger: docs.n8n.io/integrations/builtin/core-nodes/n8n-nodes-base.formtrigger
⭐ Star us on GitHub! github.com/datadrivenconstruction/DDC-CWICR