Where an employer risk event and a contractor risk event both delay completion over the same period, the position is called concurrent delay, and it is the most argued point in this field. It is also a legal question rather than a surveying one, which affects how it is handled in extension of time claim preparation.
What a surveyor can do is establish the facts clearly enough for the legal question to be answered: what happened, when, and what each event did to the governing chain.
True concurrency is rare
Genuine concurrency means two effective causes operating over the same period, each on its own sufficient to cause the delay.
Much of what is called concurrency is sequential: one event delayed the work, then another did, with the periods overlapping rather than coinciding.
Separating the two is factual work and it frequently resolves the argument without reaching the legal question at all.
Why the point matters so much
Because the usual consequence of concurrency is that time is granted and money is not, which suits neither party and settles a great deal.
Because it is the first defence raised against almost every delay claim, whether or not the facts support it.
And because contracts increasingly address it expressly, which changes the answer from the general position.
What the contract may say
Some amendments provide that where delay is concurrent, no extension is due, which is a significant risk transfer.
Others provide for apportionment, or require the contractor to show that the employer event was the dominant cause.
Reading the actual clause comes first, because a general discussion of concurrency is of no use where the contract has dealt with it.
The facts that decide it
The dates each event arose and the periods over which each affected the governing chain.
Whether the contractor risk event was itself on the critical path, which it frequently was not.
And what the contemporaneous records show about what was actually holding the work up, which is usually clearer than either party’s later account.
The commonest misuse
Asserting concurrency generally, without identifying the contractor risk event or showing that it affected completion.
That is an assertion rather than a defence, and it should be answered by asking for the particulars rather than by arguing the law.
A defence that cannot name its own delay event and show its effect is not usually worth the weeks spent arguing with it.
Where the contractor caused part of the delay
That is ordinary rather than fatal. The question is what each cause did, over which period, to the chain that governed.
A claim that quietly includes the contractor’s own period is easy to attack and damages everything around it.
Excluding it openly, and saying so, usually costs less than it recovers in credibility.
Money where time is granted
An extension protects against liquidated damages. It does not by itself produce loss and expense, which travels its own route.
Where concurrency means the money claim fails while the time claim succeeds, that is still a substantial result, and it is frequently the realistic one.
Clients are better served by hearing that at the start than by discovering it after a full submission.
Apportionment
Some contracts provide for it and in some circumstances it is the practical outcome of a negotiation whatever the contract says.
Where it is on the table, a reasoned basis for the split is worth preparing, because the alternative is a figure arrived at by haggling.
Whether apportionment is legally available on particular facts is a question for advice rather than for a surveyor’s view.
What good records do to this argument
Daily records showing what was actually preventing progress remove most of the scope for a concurrency argument in either direction.
Where the records are thin, the argument expands to fill the space, which is why this defence succeeds most often on poorly documented projects.
The cheapest protection against it is a site diary kept properly, which costs nothing and is worth more than any later analysis.
How assessors handle it
Usually by looking for what was really driving the delay in each period rather than by applying a doctrine.
A submission that sets the periods out clearly, and deals with the contractor’s own delays rather than hiding them, is easier to assess and tends to be assessed.
One that denies any contractor contribution on a project where the records plainly show some invites a harder reading of everything else.
Getting legal input at the right point
The facts come first: events, dates, effects, records. Those are needed whatever the legal position turns out to be.
The legal question is then narrow and can be answered quickly, which makes advice cheaper than it is when it has to start from scratch.
Taking advice before the facts are assembled usually produces a general answer that does not help.
What to do on a live project
Record what is holding the work up, daily, with the reason. That single habit decides more concurrency arguments than any submission.
Notify employer risk events promptly, so that the periods are established at the time rather than reconstructed.
And deal with the contractor’s own delays openly in progress reporting, because a record that only ever blames others persuades nobody later.
Where it fits
Concurrency is an argument within a time claim, and the factual work for it is the same work the claim needs anyway.
Where the clause has been amended to exclude relief, that is initial dispute review work and it comes before anything else.
The records that settle it are kept during the works, through commercial management rather than in anticipation of a dispute.
Running late with nobody agreeing why?
Extension of time claim preparation sets out the events relied on, their effect on the programme and the contractual route to relief, in a form that can be assessed rather than argued over.