The verdict in three sentences
For a finishing-trades SME with 45 staff and 120 projects a year, Odoo Enterprise is cheaper upfront: roughly 31 EUR per user per month plus 15,000 to 30,000 EUR of integration. A custom build costs 40,000 to 75,000 EUR and 4 to 6 months, but becomes competitive over five years once progress billing (Abschlagsrechnungen), 5 % retention (Sicherheitseinbehalt) and site time tracking fall outside the standard. The right choice depends less on price than on how many trade-specific processes you refuse to give up.
What a Berlin construction SME actually needs
A drywall, painting, joinery or electrical contractor in Berlin and Brandenburg juggles private and public contracts under VOB/B, subcontractors and clients paying at 30 to 60 days. The non-negotiables:
- Quotes by trade package and item with price libraries and quantity take-offs, often GAEB import for public tenders.
- Monthly progress invoices with cumulative percentages and price adjustment.
- 5 % retention tracked until release after the warranty period, or replaced by a bank guarantee.
- Time tracking per site from workers' phones.
- Real-time job costing: labour, materials, subcontracting.
Odoo covers purchasing, inventory, accounting and CRM well. Progress billing, GAEB and retention usually need third-party modules or custom development, which pushes up integration cost.
Five-year total cost of ownership
Assumption: 20 active users (office, site managers, foremen), 2026 estimates in EUR excluding VAT.
| Item | Odoo Enterprise | Custom build |
|---|---|---|
| Licences or subscription | 31 × 20 × 12 × 5 = 37,200 EUR | 0 EUR |
| Integration or initial build | 15,000 to 30,000 EUR | 40,000 to 75,000 EUR |
| Construction modules (progress billing, retention, GAEB) | 10,000 to 18,000 EUR | Included |
| Hosting over 5 years | Included in Odoo SaaS, or about 3,000 EUR on Odoo.sh | 3,000 to 6,000 EUR |
| Changes and maintenance over 5 years | 15,000 to 25,000 EUR (version upgrades included) | 15,000 to 30,000 EUR |
| Training | 3,000 to 5,000 EUR | 3,000 to 5,000 EUR |
| 5-year total | 80,200 to 118,200 EUR | 61,000 to 116,000 EUR |
The ranges overlap heavily. Odoo wins if you accept its screens and flows. Custom wins if your team already tried a package and went back to spreadsheets for progress billing.
Decision criteria beyond price
| Criterion | Odoo Enterprise | Custom build |
|---|---|---|
| Time to go live | 2 to 4 months | 4 to 6 months |
| Progress billing and price adjustment | Third-party or custom module | Built around your method |
| Mobile time tracking | Standard app, sometimes heavy | Single screen, three taps |
| Integrated accounting | Yes, full | Export to DATEV or your accounting tool |
| Dependency | Vendor and integrator | You own the code, provider replaceable |
| Version upgrades | Yearly, must be tested | At your pace |
| Trade-specific evolution | Limited by the standard | Unlimited, paid as needed |
Before choosing, ask both bidders to demo one real progress invoice from a recent project, with retention and a price adjustment line: it exposes gaps in under an hour. A hybrid path often works best at this size: keep accounting and purchasing in a standard tool with DATEV export, and build only the projects, progress billing and time tracking layer.
Mini case study
Jonas, managing director of a drywall and painting contractor in Berlin (45 staff, 120 projects a year, 8 million EUR revenue), compares two quotes.
Need a professional website?
Kolonell builds websites that attract clients, optimized for the Sénégalese market. Free quote in 2 minutes.
- Odoo: 37,200 EUR licences + 25,000 EUR integration + 14,000 EUR construction modules + 20,000 EUR changes = 96,200 EUR over five years.
- Custom projects layer: 58,000 EUR + 4,000 EUR hosting + 22,000 EUR maintenance and changes = 84,000 EUR over five years, accounting kept on the current tool.
Expected gain: progress invoices drop from 2 days to half a day per month, so 18 days a year at 420 EUR loaded cost, 7,560 EUR. Invoicing 10 days earlier on 8 million EUR frees about 220,000 EUR of cash. Jonas picks the custom projects layer, 12,200 EUR cheaper over five years.
FAQ
Is free Odoo Community an option?
Community removes the 37,200 EUR of licences but lacks the full official mobile app and vendor support. Integration and maintenance rise by about 20 to 30 %, which erodes most of the saving.
How long does a custom construction management tool take?
Allow 4 to 6 months, including 4 weeks of discovery with site managers. A first version with time tracking and job costing can run from month three.
Does a custom tool handle German e-invoicing?
Yes, if it produces XRechnung or ZUGFeRD files or feeds your compliant accounting software. Since 2025 German businesses must be able to receive e-invoices, with issuing obligations phasing in through 2027 and 2028.
How is the 5 % retention tracked?
The tool records retention on each progress invoice, computes the release date after the warranty period and alerts accounting 30 days ahead. Across 120 projects, that avoids forgetting amounts often above 100,000 EUR a year.
Can we start on Odoo and move to custom later?
Yes, but migration costs 10,000 to 20,000 EUR. Pilot the standard for three months before committing to a full rollout.
Let's scope your project. We compare standard, custom and hybrid options against your real project portfolio, with a 4 to 6 month plan. Detailed quote within 48 h. WhatsApp +221 77 596 93 33.
Mohamed Bah
Fondateur, Kolonell
Passionate about digital and entrepreneurship in Africa, Mohamed has been helping Sénégalese businesses with their digital transformation since 2020. Founder of Kolonell, he believes every SME deserves a professional and accessible online présence.
