Prevention under the NEC4 Engineering and Construction Contract

Clause 19 of the NEC4 Engineering and Construction Contract (ECC) introduces the concept of a prevention event, a contractual mechanism that addresses extraordinary occurrences disrupting performance. Although similar in effect to the common law doctrine of force majeure, the NEC4 deliberately avoids using this term and instead relies on its own defined criteria to determine the occurrence and consequences of such events. This article outlines the conditions under which clause 19.1 operates, examines the role of the project manager in managing these events, and considers the wider implications, including compensation and termination.

What is a prevention event?

Clause 19 of the NEC4 Engineering and Construction Contract (ECC) deals with prevention events.^[1] Such events are often referred to under the doctrine of force majeure, a French term meaning ‘superior force’. Force majeure is generally recognised in common law legal systems but not in English law, and the NEC4 forms do not use this term.^[2] The term ‘prevention’ is not a defined term covered by clause 11.2 of the NEC4 ECC or any other of the NEC4 contract forms. Clause 19.1 describes the effects (not the cause^[3]) of an event that qualifies as a prevention event, along with the actions to be taken.

Clause 19.1 of the ECC states:

“If an event occurs which

stops the Contractor completing the whole of the works or
stops the Contractor completing the whole of the works by the date for planned Completion shown on the Accepted Programme,

and which

neither Party could prevent and
an experienced contractor would have judged at the Contract Date to have such a small chance of occurring that it would have been unreasonable to have allowed for it,

the Project Manager gives an instruction to the Contractor stating how the event is to be dealt with.”

The first part of clause 19.1 describes two distinct scenarios that would constitute a prevention event. In the first scenario, the event must stop the contractor from completing the whole of the works and not just a part of the works. In the second scenario, the contractor must demonstrate that the date they planned to complete, as shown on the accepted programme, is no longer possible. The word “stops” indicates that there is no real possibility of completion by the planned date or at all.^[4]

The second part of clause 19.1 applies two further tests in defining a prevention event. First, the event must be one that neither party could have prevented. The parties must show that nothing reasonably could have been done to avoid the event. The NEC4 ECC User Guide argues that a subcontractor’s insolvency would likely fail this test if the contractor failed to assess the subcontractor’s financial stability or had the option not to subcontract at all. In the second test, it must have been unreasonable for an experienced contractor to have allowed for the event at tender. This introduces a foreseeability element akin to the test used for physical conditions.^[5]

Project manager’s instructions

Other than the obligation to notify of early warnings under clause 15.1, there is no requirement for the project manager to notify the contractor of a prevention event. However, clause 19.1 does require the project manager to instruct the contractor on how to deal with a prevention event. It is recommended that the project manager consult with the client and the contractor before giving any instructions. If the matter is dealt with as an early warning, such consultation and instruction will be inherent in the conduct of a subsequent early warning meeting.^[6] The project manager may issue any instruction permitted under the contract, and the contractor must obey a valid instruction.^[7] The instruction may involve removing all of the remaining work from the scope, leading to a compensation event for reduced prices, but not an earlier completion date.^[8] However, the project manager’s authority does not extend to making agreements with the contractor that change the contract.^[9]

Prevention as a compensation event

Notwithstanding any instruction by the project manager in response to a prevention event, such a matter constitutes a compensation event in its own right.^[10] Clause 61.3 requires the contractor to notify the project manager of this type of compensation event. Failure to do so within eight weeks of becoming aware that the event has happened means the contractor is not entitled to any additional time or money. It is difficult to imagine a situation where none of the relevant people would be unaware of a prevention event, but formal notification is still required to protect the contractor’s interests.

Termination following a prevention event

Clause 91.7^[11] makes provision only for the client to terminate the contractor’s obligations to provide the works following a prevention event. The reasons allowing termination mirror those stated in clause 19.1, but with the addition of a threshold of thirteen weeks forecast delay to completion of the whole works. Notably, thirteen weeks is substantially longer than other standard forms of contract.^[12] A party wishing to terminate the contract, in this case the client, must first notify the contractor and the project manager, providing details regarding the reason for termination. The project manager will then determine if the reason aligns with the terms of the contract. If the reason is deemed valid, the project manager must promptly issue a termination certificate.

Similar to the tests for a compensation event, the project manager must assess whether the event was one that "an experienced contractor would have judged at the Contract Date to have such a small chance of occurring that it would have been unreasonable to account for it." If the project manager, acting impartially, finds that the event was reasonably foreseeable, then the client’s termination under clause 91.7 would not be valid. In this case, termination may be possible under secondary option X11 (if included in the contract) or Reason 11 under clause 91.2. Alternatively, the parties may be willing to enter into a negotiated separate agreement under clause 12.3 to bring the contract to an end and agree that their respective obligations are discharged.

Conclusion

Clause 19 of the NEC4 ECC provides a structured response to rare and unforeseeable events that prevent completion of the works. While the terminology differs from traditional force majeure provisions, the effect is comparable. The clause imposes a high threshold of unpredictability and unavoidability, placing emphasis on reasoned judgement at the time of contract. The project manager’s role is central, both in issuing instructions and in certifying termination where applicable. Contractors must remain vigilant in meeting notification obligations under clause 61.3 to secure entitlement to time or monetary relief. The clause reflects NEC’s emphasis on proactive management and early warning, requiring all parties to act promptly and transparently when faced with exceptional disruption.

David Hunter
Daniel Contract Management Services Ltd

August 2025

^[1] Not to be confused with the “prevention principle”- e.g.: Peak Construction (Liverpool) Ltd v McKinney Foundations Ltd [1970]; Multiplex Constructions (UK) Ltd v Honeywell Control Systems Ltd [2007] EWHC 447 (TCC)

^[2] The JCT forms of contract use the term force majeure as a reason for termination, but do not define the term.

^[3] For example: FIDIC Red Book 2017 clause 18.1 Exceptional Events

^[4] David Thomas & Krist Lee, Keating on NEC4 (1st edn, Sweet & Maxwell 2022) para 2-205

^[5] Clause 60.1(12)

^[6] Clause 15.3 and 15.4

^[7] Clause 27.3

^[8] Clause 14.3, 60.1(1),63.3, 63.4, 63.5.

^[9] Clause 12.3.

^[10] Clause 60.1(19)

^[11] Reason 21

^[12] For example; The JCT Standard Building Contract 2016 sets a default period of 2 months in the contract particulars and one month in the Minor Works contract.

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