Commonly Used Terms

In this blog, we cover 6 common terms used in describing and discussing the effects of unforeseen events. Often, individuals define these terms based on their own experience, which can at times lead to varying definitions.

When works-on-site are subject to unforeseen events, people often describe these events with reference to the following terms:

  1. Delay
  2. Disruption
  3. Concurrency
  4. Float
  5. Critical path
  6. Contingency

In our experience, individuals tend to define each term differently. This can often result in mixed responses, discussions and debates during relevant commercial meetings.

Putting it simply in our own words:


Delay is an event that prolongs planned work. A delay can prevent the commencement or completion of an activity; or increase the duration of an activity, whether an activity has or has not started. A delay has the ability to affect and/or change the critical path; as well as change the entire sequencing of works. Delays are generally measured against a planned start/finish date as the benchmark.



Disruption is the rise in the cost of carrying out work. It is measured by comparing planned cost and actual cost or comparing actual costs arising from different circumstances (for example uninterrupted vs interrupted work).  It is therefore a measure of different productivities. Whilst delay and disruption can be related and intertwined, they can also occur without one another.


Concurrency is often the most complex event arising on a project. It is the presence of two or more delays at play.

Different forms of concurrency can arise based on the following variables:

  1. The timing of the events.
  2. The duration of the delays.
  3. The party or parties were responsible for the delays.
  4. The criticality of the delays.
  5. A delay triggers another delay.


Float is the amount of freedom that an activity has for movement (if any) beyond its planned duration. It is usually measured in days. There are 3 main types of float:

  1. Total float – the amount of freedom that an activity has for movement before it starts impacting the end date of a project. This is the most common type of float people refer to.
  2. Free float – the amount of freedom that an activity has for movement before it reaches its successor.
  3. Terminal float – the amount of freedom that a project has (if any) prior to a contractual date.

Critical path

The critical path in its simplest form is the longest path (or paths) to project completion where there is no total float available. On complex projects with multiple work fronts, separable portions staged handovers etc., the critical path (or paths) may not be straightforward.


Contingency is any period(s) of time where a contractor purposely allows for no planned work. This excludes set holidays and RDOs. It is represented as non-working days set in a calendar or blocks of time expressed as an activity. Its main purpose is to provide the contractor leeway in cases where the contractor is unable to maintain planned progress. Whilst float is generally a first come first serve basis i.e. for the benefit of either the principal or the contractor, contingency is for the benefit of the contractor only.


I hope you have found this blog helpful and if you require further clarification please do not hesitate to get in contact with us at or LinkedIn


N.b. Nothing in this article constitutes legal, professional or financial advice.