Terminal float in NEC: Ownership, Mechanics, and Reality

There's a persistent claim in construction that "the Contractor owns terminal float" under NEC. It's become shorthand advice, so let's unpack what's actually true, what's assumed, and why the distinction matters.

 

The origins of "terminal float" as a term

The term "terminal float" appears nowhere in the NEC clauses or the SCL Delay and Disruption Protocol. It originated in the NEC Guidance Notes to explain the contract's unique mechanics, not in the contract conditions themselves. It is not a defined contractual term, nor is it common scheduling terminology. It's a practitioner's label, a nickname for a mathematical result specific to NEC.

 

Historical timeline

The story starts in 1986. In Glenlion Construction Ltd v The Guinness Trust, the court ruled that while a contractor can plan to finish early, the employer has no obligation to facilitate it. That created a problem: if a contractor programmes early completion, what happens to the gap when delays occur?

NEC1 in 1993 addressed this directly by separating planned Completion from the Completion Date and requiring both to be shown on the programme.

The Guidance Notes introduced the term "terminal float" to describe the gap between the two, not the contract conditions themselves.

By 1999, Ascon Contracting Ltd v Alfred McAlpine Construction confirmed that where a contract is silent, float is generally owned by the project, highlighting just how distinctive the NEC mechanism actually was.

 

The mechanical truth

Clause 63.5 (NEC4) measures CE delay as the shift in planned Completion. This preserves the gap between planned Completion and the Completion Date. Functionally, the Client cannot absorb CE delay into that gap. That is true.

But preserving a gap is not the same as expressly conferring a legal right to it. If the contract expressly conferred ownership, there'd be nothing left to debate. The fact that people have had to reason their way to the answer is itself the evidence that it doesn't, and that the answer is not as clean cut as some would have you believe.

 

The challenges

Saying "the Contractor owns it" is incomplete.

• Terminal float only exists if it is contained within an Accepted Programme. If the Project Manager does not accept a programme under Clause 31.3, for example because it is "not practicable", that float is a ghost. You cannot own what hasn't been accepted.
• While the Client cannot use terminal float to offset Compensation Events, the Contractor doesn't own it in the way they own a piece of plant. It is effectively an entitlement to what would otherwise be a time extension, nothing more.
• Terminal float can be manipulated by the Contractor through programme construction to its benefit.
• It can be eroded by the Client through conduct, to the Contractor's detriment.
• Free float, total float and terminal float are all products of a highly subjective modelling process, open to scrutiny.
• A tribunal can disregard it precisely because it derives from theoretical modelling rather than hard fact.
• The Contractor doesn't own the time, they own the right to a robustly programmed Completion Date. If the programme fails, the ownership fails with it.

• True terminal float is often confused with Time Risk Allowance (TRA). While TRA is a discrete, quantifiable allowance attached to specific risks, terminal float is merely an "emergent" byproduct of the entire network logic. Any minor shift on the critical path can silently erode your float, whereas TRA remains a tangible, justifiable shield, provided it isn’t just a 5% "buffer" slapped onto the end of the programme.

 

Good advice means knowing where a right comes from, and being honest about what can be manipulated, eroded, and disregarded along the way.

 

Best, Radek Makar Director | ViViAD radek@viviad.co.uk

ViViAD is an independent consultancy specialising in Planning, Project Controls, Power BI Reporting, and Construction Claims Support. We work across the UK - typically on NEC contracts in defence, nuclear, renewables, and infrastructure - embedding with project teams to bring structure, clarity, and commercial control. Interim or longer-term, we fit around what you need.