The verdict in three sentences
A RAG-based internal AI assistant (retrieval-augmented generation) lets a construction group's teams ask a question in plain English and get a sourced answer drawn from 12,000 internal documents. The project costs GBP 30,000 to 55,000, then GBP 400 to 1,000 per month, and pays back within months once 300 staff use it. The non-negotiable condition: enforcing access rights per department and hosting data in line with UK GDPR.
What a RAG does, and what it costs
The principle is simple: documents are split, indexed in a vector database, and the language model answers only from the retrieved passages, with a link to the source. No document is used to train a public model. For a CIO, the budget splits between document ingestion, rights management and the interface.
| Item (2026 order of magnitude) | GBP range | Comment |
|---|---|---|
| Document audit and scoping | 3,500 to 6,000 | Inventory of the 12,000 documents, formats, owners |
| Ingestion and indexing (PDF, Word, scanned drawings) | 7,500 to 13,500 | OCR of scanned documents included |
| Access rights per department | 6,000 to 11,000 | Sync with Active Directory or Microsoft 365 |
| Web interface and Teams integration | 5,000 to 10,000 | Sourced answers, history, user feedback |
| Security, logging and compliance | 3,500 to 7,500 | Query traceability, encryption, DPIA |
| Training and change management | 3,500 to 6,000 | 20 champions trained, usage guide |
| Total project | 30,000 to 55,000 | Delivery in 10 to 16 weeks |
The monthly usage cost, GBP 400 to 1,000, covers hosting, language model calls and maintenance. It depends mainly on query volume: roughly GBP 0.10 to 0.25 per question depending on the length of the documents retrieved.
Security and UK GDPR: hosting choices
UK GDPR and the Data Protection Act 2018 govern personal data processing and international transfers, under the oversight of the Information Commissioner's Office (ICO). Employment contracts, HR files or subcontractor data are in scope. The architecture choice therefore drives compliance.
| Hosting option | Indicative monthly cost | Level of control | Compliance steps |
|---|---|---|---|
| Public cloud outside the UK/EU, standard AI API | GBP 400 to 650 | Low on location | DPIA + international transfer agreement |
| Public cloud, UK or EU region, zero-retention AI API | GBP 500 to 750 | Medium | DPIA + processor contract |
| UK data centre + model via zero-retention API | GBP 600 to 850 | Good | DPIA, transfer limited to queries |
| On-premise servers + open-source model | GBP 750 to 1,000 (excl. GPU server purchase) | Maximum | Standard DPIA |
| Hybrid: sensitive documents on-premise, rest in cloud | GBP 600 to 950 | Good, by sensitivity level | DPIA + data flow mapping |
Access rights are applied before retrieval: a site manager will never get an HR contract passage, however the question is phrased. Every query is logged for 12 months for audit.
Mini case study
James, CIO of a 900-employee construction group in London, targets 300 regular users (site managers, design office, procurement, legal). Each runs an average of 3 document searches per week, saving 25 minutes per search.
Time freed: 300 x 3 x 25 = 22,500 minutes, i.e. 375 hours per week. At an average fully loaded hourly cost of GBP 45, that is GBP 16,875 per week, about GBP 67,500 per month. Cautiously keeping only half that gain, GBP 33,750 per month, a GBP 45,000 project plus GBP 750 monthly pays back in under 2 months.
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FAQ
Can the assistant make up an answer?
RAG strongly limits this risk by forcing the model to cite its sources, and it answers "I can't find it" when no document matches. On a well-indexed corpus, the accurate answer rate reaches 85 to 92% in acceptance tests.
Can scanned drawings and sheets be used?
Yes, thanks to the OCR included in ingestion. Allow 15 to 25% of the indexing budget for scanned documents, more if drawings are handwritten.
Do we need a DPIA?
Yes, as soon as personal data is processed at scale with a new technology, the ICO expects a data protection impact assessment. It is prepared with you and usually takes 3 to 6 weeks including internal review.
How does the index stay up to date?
Automatic sync with SharePoint, the file server or the document management system reindexes new or modified documents every night. That means a few hundred documents per month for a group this size.
Can we start with a single department?
Yes, a pilot for legal or the design office, with 1,500 to 2,000 documents, costs GBP 12,000 to 20,000 and ships in 6 weeks. It then serves as the foundation for the group rollout.
Let's scope your project. Tell us your document volume, the departments involved and your hosting constraint: we price a pilot or a full rollout between GBP 30,000 and 55,000, delivered in 10 to 16 weeks. 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.
