Why M&E contractors lose commercial protection early under NEC
- Jun 9, 2025
- 6 min read
Updated: Apr 13
On NEC, M&E margin is often lost in the silent gap between a builder's delay and a contractor's commissioning window.
That gap does not appear in a disputed payment notice. It does not surface in a formal disagreement. It accumulates quietly over the course of a project as the accepted programme ages, the interfaces go unmodelled, and the commissioning block at the end absorbs weeks of lost time without anyone formally agreeing to the arrangement. By the time the M&E contractor realises what has happened, the contractual record no longer tells the story. The entitlement was real. The programme cannot prove it.
This is not a technical failure. It is a programme failure. And it is one that M&E packages are uniquely positioned to suffer.
Where interface risk becomes invisible delay
M&E contractors operate at an unusually dense intersection of dependencies. An HVAC subcontractor cannot begin duct installation until ceiling openings are cut. An electrical contractor cannot energise systems until a permit is issued. These are not risks that arrive without warning. They are structural features of the scope. The question is whether the accepted programme captures them explicitly enough to protect entitlement when they move.
When the programme shows one bar labelled "Install and commission HVAC" without modelling the predecessor activities that must be complete before that bar can start, the result is invisible delay. The ceiling openings are never cut. Installation cannot begin. But because the programme never showed "Prepare ceiling openings" as a predecessor under the main contractor's control, NEC treats the slippage as the M&E contractor's own risk. The interface was not visible, so it is assumed not to have mattered.
This mechanism applies to any M&E activity that can only proceed once something else is done: design approval, builders' work in connection, client-supplied power, a permit to work, a witness test by a third party, or a certificate of practical completion on a preceding section. Every one of those dependencies needs an explicit place in the programme logic. If it is not there, it is assumed not to exist.
The contractors who keep their commercial position intact are the ones who force those dependencies into the programme before the project starts, not the ones who argue about them afterwards. NEC is a prospective contract. It rewards parties who forecast properly, and it is systematically unkind to those who reconstruct.
The commissioning squeeze: where lost time goes
The most commercially damaging pattern on M&E packages under NEC is not the individual delay. It is the cumulative squeeze that develops around commissioning and handover.
Civil and structural works run late. Access is given to M&E later than planned. But the handover date does not move. The commissioning window, which might have represented 20 to 30 percent of the package duration at tender, is progressively compressed as construction delays accumulate upstream. The M&E contractor accelerates to make up time. The system is handed over on time, or close to it. The project is declared a success.
The M&E contractor then tries to recover the additional cost and lost time. At that point, a critical question is asked: where in the accepted programme is the evidence that commissioning was compressed? If commissioning activities were modelled as a block that simply shifted to the right as delays accumulated, and if the programme was updated consistently to show that compression against a fixed handover line, the contractual record tells a coherent story. If the programme was not maintained in that way, the story disappears.
Under clause 63.1 of NEC4, the dividing date fixes the accepted programme snapshot at the moment a change occurs. If that snapshot does not show the commissioning activities in their planned positions before the compression happened, the contractor has no prospective baseline to argue from. Housing Executive v Healthy Buildings remains instructive here: when the contractor had not presented a credible prospective forecast, the court was willing to assess using actuals, which almost always means less than the contractor planned.
Approvals, procurement and the hidden supply chain
M&E delays rarely originate on site. They originate in drawing registers, submittal logs, procurement programmes and design co-ordination sequences that the accepted programme never shows.
An air handling unit with a twenty-week lead time needs an order placed, a shop drawing issued, a review period, a client endorsement, a factory test and a delivery sequence. None of those steps are obvious from a bar labelled "Deliver AHU to site." Each of them is a potential chain-breaking event. If the programme models only the delivery and not the approval chain that precedes it, a late design review becomes the contractor's problem rather than a notifiable compensation event.
The remedy is to treat each approval, shop drawing sign-off and long-lead procurement milestone as an activity in its own right, properly sequenced into the programme logic. When the design sign-off is delayed by three weeks, every downstream activity shifts accordingly. The compensation event has a clear programme anchor. The time impact is demonstrated, not asserted.
The same discipline applies to builders' work in connection. BWIC activities sit under the main contractor's control but directly determine when M&E installation can start. An accepted programme that shows M&E installation without showing the BWIC that must precede it has handed the risk to the subcontractor without the subcontractor realising it.
The weekly sync: stopping the leak before the audit
The discipline that keeps an M&E contractor's commercial position defensible is not complicated. It requires a consistent weekly rhythm applied to the accepted programme: progress updated, logic checked against what actually happened on site, any slippage recorded against its cause, and the impact carried forward into the commissioning window.
The goal of that rhythm is not administrative tidiness. It is to ensure that when a compensation event arises, the programme already shows what happened and when, so that the CE assessment starts from a credible prospective record rather than a retrospective argument. A one-page programme narrative accompanying each update is worth more than hours of written argument produced months later. A note reading "AHU submittal cleared by architect on 5 May commissioning shifted by two weeks accordingly" is a contemporaneous record. It connects the cause to the effect before the effect becomes a dispute.
NEC's disallowed cost provisions under Options C and D mean this discipline also protects cost recovery, not only time. Missing an early warning, failing to update the programme, or leaving a delay unrecorded can result in Defined Cost being challenged as unjustified even when the underlying spend was entirely genuine.
For specialist contractors running M&E packages without a dedicated planning function, specialist contractor planning support exists precisely for this reason — to keep the programme mechanics running at a standard that protects the commercial position without the overhead of a full-time planner.
The argument in short
M&E contractors do not usually lose commercial protection because the installation was late. They lose it because the accepted programme failed to model the conditions that had to exist before the installation could move cleanly into energisation, testing and handover.
The interface chain, the approval sequence, the commissioning window and the procurement dependencies all need explicit places in the programme logic. When any of them moves, the programme must show that movement immediately, not because NEC demands bureaucratic tidiness, but because the prospective record is the only thing that keeps the CE assessment in the contractor's hands rather than the project manager's.
For a broader treatment of how the accepted programme protects entitlement across NEC packages, the article on when an accepted programme stops protecting a specialist contractor covers the mechanism in detail.
FAQ
Why do M&E contractors lose commercial protection more often than civil contractors under NEC?
Because M&E scopes involve a denser network of dependencies between their own work and what others must complete first. When those dependencies are not modelled in the accepted programme, delays within them fall on the M&E contractor by default.
What is the dividing date and why does it matter for M&E compensation events?
The dividing date under clauses 63.1 to 63.5 of NEC4 is the moment a compensation event occurs. It fixes the accepted programme snapshot used to assess the time and cost impact. For M&E claims, this means the programme must show the planned position of commissioning and testing activities at the moment the event occurs, not what happened later.
How should M&E contractors model commissioning in the accepted programme?
As explicit, logic-linked activities with clear predecessors. Plant room energisation, integrated system testing, witness tests, sectional handover and final handover should each appear as discrete activities linked to the construction activities that must be complete before they can start. When upstream delays push commissioning to the right, the programme records that compression automatically.
Is outsourced planning support practical for a specialist M&E package?
Yes. The work required to maintain a proper accepted programme on a typical specialist package adds up to roughly a day or two each month. At that scale, outsourced support costs significantly less than the margin exposure created by a stale or shallow programme. Specialist contractor planning support from £750 a month is specifically designed for this.
Is your accepted programme protecting your commissioning window?
If the M&E programme does not model interfaces, approvals and commissioning as explicit, logic-linked activities, entitlement can disappear before any formal dispute arises. Specialist planning support from £750 a month keeps the contractual record in a state that defends your position when things change.
