What Is Retention in Construction? (And Why It Matters to Builders)
Retention in construction is a percentage of the contract value — typically 3–5% — that the client holds back from each payment as security against defective work. Half is released at practical completion; the other half is held until the end of the defects liability period, which is typically 12 months later.
Retention is one of the most significant cash flow issues facing UK builders, particularly smaller contractors. On a £100,000 job at 5% retention, you'll never receive the full £100,000 until 12–15 months after the contract is placed. Understanding how retention works — and how to manage it — is fundamental to running a financially healthy building business.
How Retention Works — Step by Step
On a contract with 5% retention and stage payments, here's how the money flows on a £100,000 job:
| Stage | Gross Value | Retention Held (5%) | Amount Paid |
|---|---|---|---|
| Interim 1 — foundations and frame | £30,000 | £1,500 | £28,500 |
| Interim 2 — first fix | £25,000 | £1,250 | £23,750 |
| Interim 3 — second fix | £25,000 | £1,250 | £23,750 |
| Interim 4 — snagging and completion | £20,000 | £1,000 | £19,000 |
| At practical completion | Half retention released: £2,500 | £97,500 received to date | |
| After defects liability period (12 months) | Final retention released: £2,500 | £100,000 received in full | |
In this example, £5,000 of the builder's money is tied up throughout the contract period, and a further £2,500 remains outstanding for 12 months after the job is finished. On multiple simultaneous contracts, the cumulative retention figure can represent a meaningful proportion of a small contractor's working capital.
The Cash Flow Impact on Small Builders
Retention is the single biggest structural cash flow problem in the UK construction supply chain. The numbers tell the story:
- A builder running £500,000 of work per year at 5% retention will typically have £25,000–£35,000 of their money tied up in retention at any one time — money they have earned but cannot access.
- On a 12-month defects liability period, that money is locked up for well over a year after the work is complete.
- If the client or main contractor becomes insolvent during that period, the retention money may be lost entirely — it sits as an unsecured debt in the insolvency.
- Late release of retention — after the defects period has expired — is a common industry problem. Contractors often have to chase formally to get it released, adding administrative cost and friction.
For subcontractors working under a main contractor, the problem is compounded. The main contractor holds retention from the subcontractor, while the client holds retention from the main contractor. If the main contractor's client is slow to release, the subcontractor waits even longer.
The Legal Framework — Construction Act and JCT Contracts
Retention is governed by the terms of the construction contract, which in the UK is most commonly a form of JCT contract. Under the JCT Standard Building Contract, retention is deducted from each interim payment at the stated percentage, with release triggered by practical completion and expiry of the defects liability period.
The Construction Act (Housing Grants, Construction and Regeneration Act 1996, as amended by the Local Democracy, Economic Development and Construction Act 2009) gives contractors the right to:
- Payment notices — the client must issue a payment notice or pay-less notice within prescribed timescales, or the contractor's payment application is the sum due.
- Adjudication — fast-track dispute resolution if retention is withheld without valid reason. An adjudicator's decision is binding immediately and enforceable through the courts.
- Suspension of works — for non-payment, after giving 7 days' notice.
These rights apply to most commercial construction contracts. They do not apply to residential occupier contracts (where a homeowner commissions work on their home), though the principle of retention still commonly appears in domestic building contracts by agreement.
Industry Reform — the Ongoing Campaign
For decades, the construction industry has campaigned for reform of retention practices. The core demand is that retention money should be held in a ring-fenced, trust account — separate from the client's or main contractor's operating funds — so that it cannot be lost in an insolvency. This reform has been recommended by multiple government reviews, but as of 2026 mandatory retention deposit schemes have not been legislated in England.
The Aldous Bill (a private member's bill promoting retention deposit schemes) received significant industry support and several readings in Parliament. The debate continues. In the meantime, builders have to work within the current framework — understanding their rights under the Construction Act and chasing retention promptly when it falls due.
Retention in Practice — 32 Years of Experience
Retention is one of those aspects of construction finance that sounds reasonable in theory — "hold back a small amount as security against defects" — and becomes genuinely burdensome in practice, particularly as you scale. The bigger your turnover, the more retention is tied up at any one time.
My advice to builders: track your retention balances on every contract, diary the release dates, and issue formal notification when practical completion is achieved and again when the defects liability period expires. Don't wait for the client to release it — they often won't, not out of malice but simply because they're dealing with other things. A polite, formal letter requesting the first retention tranche at practical completion and the second at month 12 keeps it moving.
And read the retention clause in your contract before you sign. A 5% retention on a 12-month defects period is very different from 3% on a 6-month period. Both the rate and the period are negotiable on larger contracts, particularly if you have a strong track record with the client.
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Try RenoCalc FreeFrequently Asked Questions
What is the standard retention percentage in UK construction?
The most common retention rate is 5% of the gross value of each interim payment, held throughout the contract period. At practical completion, half (2.5%) is released. The remaining half (2.5%) is held until the end of the defects liability period, typically 12 months after practical completion. Some clients and larger main contractors negotiate 3% retention, particularly on lower-risk projects or with contractors with a proven track record.
When is retention money released?
Retention is released in two tranches. The first half at practical completion — when the project is substantially complete and the client takes possession. The second half at the end of the defects liability period, usually 12 months after practical completion, once snagging and defects have been rectified. The contractor should formally request release of each tranche — it is not always released automatically, and delays in chasing can mean the money sits unclaimed for months.
What legal protection do builders have if a client refuses to release retention?
Under the Construction Act, contractors have the right to adjudication as a fast-track dispute resolution mechanism. If a client refuses to release retention without valid reason after the trigger date, the contractor can refer the dispute to adjudication — the decision is binding immediately and enforceable through the courts. Contractors should ensure their contract clearly states retention release dates, and should issue formal payment applications with the correct dates to trigger the Construction Act's payment notice requirements.
Is there a legal requirement to hold retention in a separate account?
No — in England, there is currently no legal requirement to hold retention in a ring-fenced account. This means retention can be lost if the client or main contractor becomes insolvent. Reform proposals have repeatedly called for mandatory retention deposit schemes, but as of 2026 these have not been enacted in England. This is a live policy debate in the construction industry, with strong calls from contractor bodies for legislative change.
What does the JCT contract say about retention?
Under JCT Standard Building Contracts, retention is held as a fiduciary obligation — the client holds it on trust for the contractor but is not required to keep it in a separate account unless the contract specifically states this. The JCT contract sets out the retention percentage, the trigger dates for release (practical completion and expiry of the rectification period), and the procedures for issuing the final certificate. For authoritative JCT contract information, see: JCT Ltd — Joint Contracts Tribunal.
How should builders track and chase retention?
Keep a retention schedule for every active and recently completed contract — recording the gross retention held, the practical completion date (when half is due), and the defects liability period expiry date (when the balance is due). Diary both dates. At each trigger date, issue a formal written request for release referencing the contract terms. If release is not made within the agreed period, issue a payment application under the Construction Act and be prepared to escalate to adjudication if necessary.
