Practical Completion and Defects Liability

Understanding the contractual watershed — what changes at PC, the defects liability period, and the QS’s financial role

Introduction

Practical completion is the single most important milestone in a construction contract. It is the moment when the project transitions from the contractor’s responsibility to the employer’s — and it triggers a cascade of contractual, financial, and legal consequences that the quantity surveyor must understand and manage. Retention is released. Liquidated damages cease. Insurance responsibility transfers. The defects liability period begins. The clock starts ticking on limitation periods. For the QS, practical completion is not just a certificate — it is the pivot point around which the entire post-contract financial settlement revolves.

What is Practical Completion?

Practical completion (PC) marks the point at which the contractor has substantially finished the works in accordance with the contract, subject only to minor patent defects. Under JCT contracts, practical completion is not statutorily defined — it is a matter of professional opinion for the contract administrator. The works do not need to be perfect; they need to be practically complete for the employer’s intended use. Minor snagging items do not prevent PC. Incomplete work does.

Under JCT SBC 2024, Clause 2.30 provides for the contract administrator to certify practical completion when the contractor has substantially completed all work and complied with contractual conditions (including supply of as-built drawings and health and safety file information). Under NEC4 ECC, completion is achieved when the contractor has done all the work the programme shows, provided any remaining defects do not prevent the client from using the works or others from doing their work. The NEC approach is more pragmatic — functional completion, even with minor defects, can constitute completion. For a detailed comparison of how JCT and NEC handle these processes, see our article on Contract Administration: JCT vs NEC.

Snagging

Snagging is the inspection process that identifies minor defects, omissions, and non-conformances in the works around the time of practical completion. It typically takes place one to two weeks before anticipated PC, with the contract administrator (and often the QS) walking through the building to compile a snagging list of outstanding items — missing finishes, non-functioning elements, minor surface damage, incomplete commissioning.

The critical distinction is between snagging items (minor non-conformances that do not prevent PC), incomplete work (parts of the contract not yet executed, which do prevent PC), and defects (work that does not meet the contract specification, which are addressed during the defects liability period). A paint touch-up is a snagging item. An entire undecorated room is incomplete work. Paint that deteriorates due to poor preparation is a defect. The QS’s role in snagging is to assess the cost implications of outstanding items, flag anything that affects retention release, and estimate the cost of rectification if the contractor fails to make good.

Effects of Practical Completion

Practical completion creates a contractual watershed, triggering multiple consequences simultaneously.

Retention release. Upon certification of PC, the first moiety (typically 50%) of the retention held must be released to the contractor. On a standard 5% retention, this means 2.5% of the contract sum becomes payable — a significant cash injection for the contractor and a key commercial milestone. The remaining 50% is held until the certificate of making good is issued at the end of the defects liability period.

Liquidated damages cease. The employer’s right to recover liquidated damages (LADs) stops at the date of the PC certificate. Any LADs accrued up to PC remain due, but no further LADs can be charged. If PC is achieved mid-month, the QS must calculate the daily rate precisely. For partial possession, LADs reduce proportionally for the part taken into possession. For more on how retention works in construction contracts, see our article on Retention in Construction Contracts.

Insurance responsibility transfers. Risk of loss or damage to the works passes from the contractor to the employer at PC. Under JCT Insurance Option A, the contractor insures until PC, then the employer takes over. The contractor remains responsible for making good any defects it caused, but new loss or damage post-PC is the employer’s risk. The case of English Industrial Estates v George Wimpey (1973) confirmed that the contractor remains liable for damage pre-PC even if the employer has taken partial occupation, provided no PC certificate has been issued.

The defects liability period commences. The rectification period (JCT terminology from 2016 onwards) or the period to the defects date (NEC) begins on the date of the PC certificate. Typically 12 months under JCT and 52 weeks under NEC4, this is the period within which the employer must notify defects to the contractor for rectification at no cost.

The limitation period starts. The statutory clock for bringing breach of contract claims begins running from PC. Under a simple contract, the employer has six years; under a contract executed as a deed, twelve years. This is particularly significant for latent defects that may not be discovered for several years.

The Defects Liability Period

The defects liability period (DLP) — renamed the rectification period under JCT 2016 onwards — is the contractor’s opportunity and obligation to make good defects identified after practical completion. Standard duration is 12 months under JCT (variable in the contract particulars; 6 months for small projects, 18–24 months for complex ones) and 52 weeks under NEC4. During the DLP, the contract administrator notifies the contractor of defects as they are found, and the contractor must attend and rectify within a reasonable time — typically 2–4 weeks from notification.

The cost allocation is clear: the contractor bears the cost of rectifying defects (work not conforming to the contract specification), while the employer bears the cost of normal maintenance, wear and tear, and any damage caused by the employer’s own use. The QS advises on the allocation where items are disputed — is this a defect (contractor’s cost) or a variation (employer’s cost)?

Crucially, defects notified after the DLP expires carry no contractual obligation for the contractor to rectify. The employer’s remedy becomes a damages claim for breach of contract, subject to the limitation period. This creates urgency for the employer to inspect thoroughly before the DLP ends.

Partial Possession and Sectional Completion

Partial possession occurs when the employer takes occupation of part of the works before overall practical completion — an ad hoc arrangement requiring the contractor’s written consent under JCT. Sectional completion is planned from the outset, with the contract structured to provide for completion of distinct sections on different dates. Both trigger the same contractual consequences for the relevant part: retention release, LAD cessation (proportional reduction), insurance transfer, and a separate DLP.

For the QS, partial possession and sectional completion create significant commercial complexity. Multiple retention accounts must be tracked, with partial releases at different dates. LADs must be pro-rated. Different DLP end dates mean different making good deadlines and potentially different final account timelines. Insurance responsibility transfers piecemeal. The QS must document clearly when partial possession is taken, obtain the formal certificate for each section, and maintain separate records for each section’s defects and retention. For more on the broader contractual framework, see our article on NEC4 Engineering and Construction Contract Explained.

Making Good Defects

Near the end of the defects liability period, the contract administrator compiles a schedule of defects — a formal list of all defects identified during the DLP that have not yet been rectified. The contractor is provided with the schedule and given a reasonable time to make good all items. Once the contract administrator is satisfied that all defects have been rectified, they issue the certificate of making good (formerly the certificate of making good defects). This certificate triggers the release of the second moiety of retention — the remaining 2.5% on a standard 5% retention — and clears the path to the final certificate.

If the contractor fails to make good, the employer can employ others to carry out the rectification work and recover the cost from the contractor, either by deduction from sums due or through adjudication. The QS’s role is to estimate the cost of making good, assess whether retention is adequate to cover it, and prepare the financial case for recovery if needed. A common risk is that the cost of making good exceeds the retention held — particularly on complex projects where significant defects emerge late in the DLP. The QS should flag this to the client early.

The Final Certificate

The PC certificate and the final certificate are distinct documents with very different effects. The PC certificate confirms the works are substantially complete and triggers the DLP. The final certificate is issued much later — after the DLP has expired, all defects have been made good (or the certificate of making good has been issued), the final account has been agreed, and all claims and counterclaims have been settled. The final certificate states the final contract sum, releases all remaining retention, and has conclusive effect under JCT — meaning it is the last word on the financial position, subject only to disputes already commenced or challenged within 28 days. For more on the final account settlement process, see our article on Final Accounts and Settlement in Construction.

Latent vs Patent Defects

Patent defects are visible or discoverable by reasonable inspection at practical completion — surface cracks, incorrect finishes, malfunctioning equipment. They are identified during snagging or the DLP, and the contractor has a contractual obligation to rectify them at no cost to the employer. Latent defects are hidden — poor-quality work within cavity walls, structural defects not evident under normal inspection, design flaws that emerge only through extended use or seasonal change. Latent defects may not surface for years.

The contractual treatment differs fundamentally. Patent defects are dealt with during the DLP. Latent defects discovered after the DLP carry no contractual right to rectification — the employer’s remedy is a damages claim for breach of contract, subject to limitation periods (six years for a simple contract, twelve years for a deed). The landmark case of Hoenig v Isaacs (1952) established that a contractor is entitled to payment if the work is substantially complete, with the employer’s remedy for remaining defects being the cost of making good — not rejection of the entire contract. The QS should advise clients to obtain building warranty insurance (such as NHBC for residential) to provide protection beyond the standard limitation period.

The QS Role

The QS’s involvement spans the entire practical completion and defects lifecycle. Before PC, the QS monitors completion progress, calculates retention held, prepares the anticipated final account, and advises on likely making good costs. At PC, the QS attends the snagging inspection, calculates the first moiety retention release, computes final LAD amounts, and prepares the interim financial statement at the PC date. During the DLP, the QS tracks the schedule of defects, assesses the cost of making good each item, advises on whether disputed items are defects or variations, and monitors whether retention is adequate to cover rectification costs.

After the DLP, the QS processes the second moiety retention release once the certificate of making good is issued, prepares the detailed final account, reconciles all payments, applies all adjustments (variations, LADs, claims), and advises on any latent defects that emerge post-DLP. For more on how interim valuations and payment certification work during construction, see our article on Interim Valuations and Payment Applications.

Common Issues

PC disputes. The contractor believes practical completion has been achieved; the contract administrator disagrees. These disputes often hinge on whether outstanding items are minor snagging (which do not prevent PC) or incomplete work (which does). The QS should advise the contract administrator on the commercial implications of delayed PC — continued LAD accrual, deferred retention release, and programme impact — and help establish a realistic remediation timeline.

Retention adequacy. If the cost of rectifying defects exceeds the retention held, the employer faces a shortfall. On a £5m contract with 5% retention, the second moiety is £125,000 — which may be insufficient if significant defects emerge. The QS should forecast making good costs realistically and flag any shortfall early. For higher-risk projects, consider negotiating a higher retention percentage or requiring a performance bond.

Insurance gaps. If the employer does not have insurance in place at the moment PC is certified, there is a gap in cover. The QS should ensure that insurance transfer is addressed in the PC certification process and that the employer’s cover is confirmed before the certificate is issued.

DLP expiry. The defects liability period is fixed once the PC date is known — typically 12 months. It does not automatically extend. Defects not notified before the DLP expires lose their contractual remedy. The QS should flag the DLP expiry date to the client well in advance and encourage a comprehensive inspection before the deadline.

Practical Tips

Establish a pre-completion inspection schedule. Plan snagging inspections at least two weeks before the anticipated PC date, giving the contractor time to address outstanding items before the certificate is due.

Document everything in writing. Reasons for refusing PC, snagging items, defect notifications, rectification progress, retention calculations, and insurance transfers should all be formally documented. Contemporaneous records prevent disputes.

Track retention meticulously. Maintain a retention schedule showing cumulative retention held, first moiety release at PC, second moiety release at making good, and any adjustments for partial possession or sectional completion.

Advise on building warranties early. For latent defect protection beyond the limitation period, clients should obtain building warranty insurance at the outset — not as an afterthought.

Inspect thoroughly before the DLP expires. The DLP is a fixed period with a hard deadline. Any defects not notified before expiry lose their contractual remedy. Schedule a comprehensive inspection well before the end date.

APC Relevance

Practical completion and defects liability falls within the RICS APC competencies of Contract Administration (managing performance against contract provisions, certification of PC and making good, DLP management), Financial Management (retention management, interim and final account preparation, cost forecasting for making good), Commercial Management (advising on partial possession implications, contract strategy, retention adequacy), and Risk Management (identifying PC and defects risks, mitigating retention shortfalls, managing insurance transfer). APC candidates should be able to describe their role in assessing PC readiness, explain how they managed retention release, discuss any disputes over defect classification, and demonstrate how they prepared the final account post-DLP.

Further Reading on ProQS

Contract Administration: JCT vs NEC — how practical completion, defects, and certification differ under each contract family.

Retention in Construction Contracts — retention mechanics, release mechanisms, and the trust status debate.

Final Accounts and Settlement in Construction — the final account process that follows practical completion and making good.

Interim Valuations and Payment Applications — the payment certification process during construction and at PC.

Key References

Designing Buildings Wiki: Defects Liability Period — comprehensive UK reference on the DLP, contractor obligations, and remedies.

JCT: Practical Completion Guidance — JCT’s own guidance on what constitutes practical completion under their standard forms.

NEC: Defects Management in ECC — NEC guidance on defects, the defects date, and contractor liability.

Pinsent Masons: Practical Completion and Certificates — legal analysis of PC certification, the final certificate, and their effects.

Designing Buildings Wiki: Final Certificate — reference on the final certificate, its conclusive effect, and limitations.