Concurrent Delay: The Mirage That Costs Millions

Two delays walk into a project. Who pays?

Scene from site life: the access tunnel collapses after heavy rain. At the same time, the contractor’s transformer order is four months late. Both hit the critical path. The contractor waves his arms—“Employer delay! Force majeure! Give me time and costs.” The employer folds his arms—“Your delay cancels mine.” And suddenly, a simple slip in programme becomes an arbitrator’s puzzle worth millions.

What the law actually says

Different jurisdictions have wrestled with concurrency differently. Three big schools of thought:

• Malmaison approach (UK, Henry Boot v Malmaison, 1999)
  If there’s true concurrency (employer delay + contractor delay), the contractor gets time but no money. EOT is granted, but prolongation costs are denied.
  This is the FIDIC flavour too: no LDs, but no cost recovery either.

• Apportionment approach (Walter Lilly v Mackay; some NEC contracts)
  Delays are split in proportion to blame. Employer pays for their share, contractor eats theirs.
  Planners love this, lawyers less so. Because “splitting” delay days sounds neat, but proving percentage contribution is a battlefield.

• Dominant Cause approach (City Inn v Shepherd, 2007 Scotland; “but-for” logic)
  Where delays overlap, the tribunal identifies the dominant effect. If employer delay is dominant, LDs fall away. If contractor delay is dominant, no EOT.
  This is rare, but when applied, it can flip outcomes dramatically.

What this looks like in practice

If turbine drawings were delayed by six months (employer’s fault). At the same time, the contractor had already under-mobilized civil works. The tribunal took a Malmaison view: gave the contractor EOT (so LDs fell away), but denied prolongation costs—because he was late anyway.

On another job, an arbitrator leaned towards dominant cause: the employer delay was “administrative,” but the contractor’s slow mobilization was the real bottleneck. Result? No EOT.

Industry expert insights

• Planners hate ambiguity: If you don’t lock down concurrency methodology at the contract stage, you’re leaving it to a tribunal lottery.

• Records are king: To prove concurrency, you need critical path schedules, resource histograms, and contemporaneous diaries. “We were generally delayed” never wins.

• The money fight: EOT is often granted more easily than costs. Arbitrators want a smoking gun to give money, but are more willing to knock out LDs.

• Concurrent disruption is next frontier: It’s not just about time—what if two causes concurrently hit productivity? The law is still foggy here, but contractors are starting to test it.

  
  Concurrent delay is like two excavators digging opposite ends of a tunnel—you only meet in the middle if the programme proves it.

Concurrency isn’t about “both sides at fault.” It’s about which story the programme tells—and which doctrine your tribunal believes in.