← All case studies Construction · Fit-out + commercial main contractor · Birmingham

£184,200 of stuck retentions chased to payment. 78% of subbie WhatsApp answered without the QS. 90 days.

A Birmingham mid-size main contractor — fit-out and commercial, around 40 staff, £18M turnover, two live framework jobs and three private projects — plugged in our Site Office agent on a Wednesday. By the second week, the junior QS had stopped his 6pm scroll through 84 unread WhatsApps. A subbie asking what colour the mechanical plant room walls were got an answer from the drawing register inside 45 seconds, with the actual extract. In 90 days the agent answered 78% of subbie and supplier WhatsApp queries straight from the programme and drawing register without touching the QS, chased £184,200 of stuck retentions to payment using statutory Construction Act letter sequences, and gave the commercial team back half a week each. No AI commits the firm to a price or a date — that's still a human's job. The agent fetched and routed; the humans signed.

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1,847
Subbie + supplier WhatsApp / email queries answered
78%
Of them auto-handled with zero QS time
£184,200
Of stuck retentions chased to payment

Before: 84 unread WhatsApps and £620K in retention purgatory

  • The junior QS was a glorified drawing-register operator. 60% of his day was fetching answers off SharePoint. The senior QS was supposed to be on claims and variations — kept getting pulled into the WhatsApp queue too.
  • £620K of retention sitting past the 12-month mark. The commercial director knew it. Nobody had time to write the statutory letters. Every year-end it got written off in chunks.
  • Subbies waited four hours for a one-line answer. Most of the questions had a real answer sitting in Procore or on the drawing register — but nobody was paid to be the WhatsApp librarian.

What we plugged in

Two of our AI agents, wired into the contractor's existing Procore, the master programme in Asta Powerproject, and the firm's SharePoint drawing register. No new project-management system, no replacement accounting stack. Letter sequences were drafted by the firm's commercial counsel once and approved before any of them went live.

Site Office (CLOSER)

Read every inbound subbie + supplier WhatsApp and email, classified the query (programme date, spec lookup, drawing request, RAMS request, payment status) and pulled the answer straight from Procore + the SharePoint drawing register + the master Asta programme. Replied in 45 seconds on average, with the actual document extract attached. Hard rule: never committed the firm to a binding price, programme date, or variation. Anything commercial got flagged to the QS with a one-line summary, waiting for human sign-off.

Retention Chase (LEDGER)

Ran the back-book of stuck retentions over the 12-month mark. Sent the statutory pay-less notice letter sequence (HGCRA 1996 + LPCDA 1998) on a 7-day cadence: first letter (polite request with release schedule), 14-day chase (formal demand citing the Act), 28-day final notice (statutory interest + 8% above base). Sequences signed off by the firm's commercial counsel — the agent just ran the calendar.

The numbers, week-by-week

14-day rolling average — first 90 days vs the prior 90 days. Honest range, not the sales-deck number.

Subbie query first-reply time 4h 12m (before) 52s (after)
QS WhatsApp time / week 14 hrs / wk (before) 3 hrs / wk (after)
Retention recovered (90-day) £18K (before) £184K (after)
Commercial queries human-signed ~40% (before) 100% (after)

"The junior QS got his job back. He's actually pricing variations again rather than fetching drawing extracts off SharePoint. And the retention chase paid for itself twice over in 90 days — we got back money we'd already written down. The bit I was nervous about was the agent committing us to a date or a price. It doesn't. It literally cannot — that's the hard rule. If anything looks commercial it stops and asks. The subbies don't know it's an agent. They just know they get answers in under a minute, which is two hours faster than we used to manage."

— Commercial Director, Birmingham fit-out & commercial contractor (DC)

[2026-03-19 14:08:14] Retention Chase → outstanding retention £18,400 on Project HBR-22 (PC 2025-02-12, 12-month release due 2026-02-12, 35 days overdue) → letter sequence step 2 (14-day chase, formal demand citing HGCRA 1996 s.110A + LPCDA 1998 statutory interest at 8% above base) → letter PDF generated from approved counsel template, sent to Employer's QS 14:08:21 cc'd to Commercial Director → reply 2026-03-21 09:14: "noted, included in next valuation cycle, release scheduled 2026-04-04" → outcome 2026-04-03: £18,400 received via BACS, retention discharged, sequence closed.

— Retention Chase log, day 41

Plumbed into what they already used

  • Procore
  • Asta Powerproject
  • SharePoint (drawing register)
  • Sage Construct
  • WhatsApp Business
  • Outlook
  • DocuSign
  • BACS / Stripe (retention receipts)

No new PM system. No replacement drawing register. The commercial workflow is unchanged — the agent sits on top of it.

About this case study: Composite based on outcomes across 3 similar UK main-contractor / fit-out firms (£10M–£40M turnover, 25–80 staff) over the 90 days to 2026-04-30. Names changed. Individual results vary. The AI Site Office agent never commits the firm to a binding price, programme date, or variation — commercial responses are always human-signed. Statutory letter sequences reference the Housing Grants, Construction and Regeneration Act 1996 and the Late Payment of Commercial Debts Act 1998. Underlying numbers anonymised and rounded. More like this: construction sector page · Leeds accountancy story.

Your QS isn't a drawing-register operator. Stop treating them like one.

If your QS team is spending more than 30% of the day fetching answers subbies could find themselves if SharePoint wasn't a maze, the calculation here repeats. And if you've got more than £100K of retention older than 12 months sitting on the cash flow, the Retention Chase sequence usually pays the agent for the year inside the first 60 days. Setup is about four weeks because the integrations (Procore, Asta, SharePoint, your accounting stack) are properly mapped — we don't fake it with scraped PDFs. Letter sequences get signed off by your commercial counsel before any go live.

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