Concurrent delay is where contractors lose entitlements they actually hold, because they misread how time and money behave when two causes overlap. The instinct is that the delays simply cancel out. That is wrong: it costs the extension of time a contractor was owed, and can expose it to avoidable liquidated damages.
Key takeaways
- Concurrent delay usually gives you an extension of time for the overlap period, but not the prolongation cost for it.
- Genuine concurrency needs two delay events that are each independently critical, one at employer risk and one at contractor risk.
- Treating concurrency as a wash and staying silent is the error that destroys a real entitlement to time.
- Protect your position with an updated critical-path programme, timely notices of every employer risk event, and cause-specific records.
In this article (5 sections)
The reason this matters commercially is straightforward. Time and money are decided by different tests, and they frequently give different answers. An extension of time protects you from liquidated damages; prolongation cost recovery protects your margin. These are two separate entitlements decided by two separate questions, a distinction set out in full in EOT vs Prolongation.
Concurrent delay is the situation where those two entitlements most often diverge: you win the time and lose the money. A contractor who does not grasp that divergence will either fail to claim the time it is owed, or wrongly assume that winning the time guarantees the cost. Both errors are avoidable.
What Concurrent Delay Actually Is
True concurrent delay, in the strict sense, is where two or more delay events occur at the same time, each of which would independently have caused critical delay to completion, with one at the employer's risk and the other at the contractor's risk.
The classic illustration is a two-week period where the employer fails to provide access to a critical work area, while over those same two weeks the contractor's own labour shortage would independently have prevented progress on that same activity. Neither party could have finished on time during that window even without the other's delay.
The strict definition matters because "concurrent" is used loosely on site to describe any two things going wrong at once. Genuinely concurrent critical delay is rarer than everyday usage suggests. Much of what is called concurrency is actually sequential delay, where one cause sits on the critical path and the other does not, or where the two causes affect different activities and only one is truly driving the completion date.
The discipline is to establish which delay was truly critical, over which period, and whether a competing cause was genuinely critical during the same window - which is why the choice of delay analysis method matters so much, a subject covered in Delay Analysis Methods Explained. Get the criticality analysis wrong and the concurrency argument is built on sand.
Why Time and Money Are Decided Differently
The heart of concurrent delay is that entitlement to time and entitlement to cost are governed by different principles. Extension of time is generally decided by a causation test: did an employer risk event cause critical delay to completion? Prolongation cost is decided by a different test: did the contractor actually incur additional cost from that event, and would it have incurred that cost anyway because of a concurrent contractor delay?
The prevailing approach in international practice, reflected in the Society of Construction Law Delay and Disruption Protocol, is that where an employer delay and a contractor delay are truly concurrent, the contractor gets an extension of time for the concurrent period but cannot recover the prolongation cost of that period.
The logic: the extension protects the contractor from liquidated damages for a delay that was partly the employer's responsibility, but the contractor should not recover time-related costs it would have incurred anyway because of its own concurrent delay. In short, the contractor keeps the time but not the money - the deliberate result of a causation test for time and a but-for cost test for money.
This is an area where the law differs between jurisdictions and where the specific wording of the contract can change the outcome. Some contracts expressly allocate concurrency risk, and some legal systems approach apportionment differently. The principle above is the common starting point in FIDIC-based international practice - a starting point, not a universal rule, so the applicable law and contract terms must always be checked.
The Trap: Assuming Concurrency Cancels Everything Out
The most damaging misconception is that concurrent delay is a wash - that because both parties contributed, neither has any entitlement, so the safest course is to say nothing. This is wrong in both directions.
It is wrong because the contractor usually does have an entitlement to time during a period of genuine concurrency, and failing to claim it leaves it exposed to liquidated damages for a delay that was partly the employer's responsibility. It is also wrong because the belief encourages contractors to stay silent - to skip notices and skip the contemporaneous records a concurrency analysis depends on.
The practical consequence is that contractors under-claim. They see their own delay running alongside the employer's, conclude they have no case, and never notify the employer delay at all. At the end of the project, the employer levies liquidated damages for the full overrun.
The contractor then discovers too late that a properly notified and analysed concurrency argument would have secured an extension of time covering a substantial part of that overrun. The entitlement existed. The silence destroyed it. The same notice discipline that governs every other time-sensitive entitlement applies here too, as covered in The 28-Day Rule.
What This Means for Your Records and Notices
Concurrent delay is won or lost on the quality of the contemporaneous programme records, because the argument turns on establishing what was critical, when, and why. To preserve its concurrency position, the contractor must do three things from the outset:
- Maintain an updated programme that shows the critical path and how it moves as the project progresses, so each delay event's criticality can be demonstrated rather than reconstructed.
- Notify every employer risk event as it arises, regardless of whether a contractor delay is also running, because the right to an extension of time depends on the notice being given.
- Keep cause-specific records that let an analyst separate the employer delay from the contractor delay, since a concurrency argument that cannot distinguish the two causes will fail.
Where a concurrency dispute has already crystallised, independent forensic delay analysis is what resolves it, and that forensic capability is the core of CALIM's delay analysis and dispute support.
The contractor should also resist the temptation to overstate concurrency in its own favour. Tribunals and engineers are alert to the tactic of labelling every contractor delay as concurrent with some employer event to escape liquidated damages. A concurrency argument that does not survive a criticality analysis damages the contractor's credibility on the rest of the claim.
The honest position, supported by the records, is far stronger than an aggressive one that collapses under scrutiny. Where the analysis genuinely supports concurrency, claim the time confidently. Where it does not, do not manufacture it.
Where the employer alone causes the delay and the contract offers no way to extend time for it, a different rule takes over: the prevention principle can stop the employer holding the contractor to the original completion date at all.
Frequently Asked Questions
What is concurrent delay in construction?
Concurrent delay, in the strict sense, is where two or more delay events happen at the same time, each of which would independently have caused critical delay to completion, and where one is at the employer's risk and the other is at the contractor's risk. During that period neither party could have completed on time even without the other's delay. Much of what is loosely called concurrency is in fact sequential delay, where only one cause is truly on the critical path, so establishing genuine concurrency requires a careful criticality analysis of the programme.
Can a contractor claim an extension of time for concurrent delay?
In most FIDIC-based international practice, yes. Where an employer delay and a contractor delay are truly concurrent, the contractor is generally entitled to an extension of time for the period of concurrency, because an employer risk event caused critical delay to completion. The extension protects the contractor from liquidated damages for that period. However, this depends on the governing law and the specific contract terms, some of which allocate concurrency risk expressly, so the position should always be confirmed against the applicable contract and jurisdiction.
Can a contractor recover prolongation costs during concurrent delay?
Usually not for the period of genuine concurrency. The prevailing approach, reflected in the SCL Protocol, is that the contractor recovers an extension of time but not the time-related prolongation cost of a concurrent period, because it would have incurred those costs anyway due to its own concurrent delay. This is why time and money diverge in concurrency: the contractor keeps the time but not the money. The precise outcome varies by jurisdiction and contract wording, so the cost position should be assessed case by case.
Does concurrent delay mean the two delays cancel each other out?
No, and this is the most expensive misconception. Concurrency does not mean neither party has any entitlement. The contractor usually retains an entitlement to an extension of time for the concurrent period, which protects it from liquidated damages, even though it may not recover the associated prolongation cost. Assuming the delays simply cancel out leads contractors to stay silent, skip notices, and lose the time entitlement they actually held, exposing themselves to liquidated damages that a properly argued concurrency claim would have prevented.
What records do I need to prove concurrent delay?
You need a contemporaneously updated programme that shows the critical path and how it moves, so the criticality of each delay event can be demonstrated rather than reconstructed after the fact. You also need timely notices of every employer risk event, and cause-specific records that allow an analyst to separate the employer delay from the contractor delay over the relevant window. Because concurrency turns entirely on what was critical, when, and why, the strength of the argument is directly proportional to the quality of the programme and delay records kept at the time.
Concurrent delay does not forgive both sides equally. It usually gives you the time and withholds the money, and only if you claimed it. Silence is the one response that guarantees you lose both.
Note: This article provides general information on concurrent delay and is not legal advice. The treatment of concurrent delay differs between jurisdictions and depends on the governing law and the specific terms of the contract, including any express allocation of concurrency risk. Contractors should obtain advice tailored to the particular contract, project records, and applicable law before relying on any concurrency position.
Tools and next steps for this topic
CALIM Contracts Desk
Contracts, Claims & Commercial Advisory
Reviewed for accuracy by CALIM's senior leadership: Dr. Varghese Koshy Panicker (Founder & CEO), Adv. Jayakumar Madapattu (Co-Founder & CLO), Tins Varghese (Co-Founder & CCSO).
This article is general information about construction contract practice, not legal advice. Entitlement, notice requirements and time bars turn on the specific wording of your contract and the governing law, which vary between projects and jurisdictions. Obtain advice tailored to your contract before acting on anything set out here.