Start here, lesson 1
Delay, disruption and quantum explained
Delay is about time. Disruption is about efficiency. Quantum is about money. A crew can lose productivity without delaying completion, and a project can finish late without the claimed event reducing anybody’s productivity at all.
- Jurisdiction
- General; the contract mechanisms named are jurisdiction specific
- Law and editions as at
- 3 August 2026
- Last reviewed
- 3 August 2026
- Editorial status
- Editorial draft, not yet independently reviewed
Delay
Delay is the movement of a completion date or a contractual milestone. The question it asks is whether an event affected the work that was controlling completion at the relevant time. Notice that the definition contains no money at all. An extension of time moves a date, and its practical value is protection from liquidated damages for the extended period.
Disruption
Disruption is loss of efficiency: the same work taking more resource than it should have, because something changed the conditions in which it was done. Restricted access forcing smaller work fronts, stop and start installation caused by late design, repeated changes causing demobilisation and relearning. Disruption can happen on work that was never on the critical path, which is exactly why it is a separate question.
Prolongation
Prolongation is the time-related cost of being on site longer during a compensable period: site staff, accommodation, plant standing, facilities, insurances and bonds. It is proved with actual cost records for the period, not by multiplying a day rate by the number of days in an extension. Extended duration and inefficient working are different things and are proved differently.
Quantum
Quantum is the umbrella term for the money question: what additional cost or loss is recoverable, on what contractual or legal basis, proved to what standard. It sits downstream of entitlement. Establishing that an event occurred, and even that it caused delay, does not establish that the money follows.
Why the distinction is not academic
Each of the four needs a different proof. Confusing them produces claims that are internally inconsistent, and a claim that asks for prolongation cost while proving disruption, or claims disruption using programme evidence, invites the response that the claimant does not know what it is claiming.
| Question | Delay | Disruption | Prolongation |
|---|---|---|---|
| What changed? | Completion or milestone timing | Efficiency and productivity | Duration-related resource use |
| Core proof | The event affected then-critical work | The event altered how resources produced output | A compensable duration caused actual additional cost |
| Typical data | Programmes, progress, sequence | Labour hours, quantities, crews, workface conditions | Ledgers, payroll, plant, site staff, invoices |
| Common mistake | Counting any late activity as delay | Equating an overrun with owner-caused inefficiency | Rate multiplied by extension days, with no actual cost or causation |
The rule that follows from all of it
Time entitlement and money entitlement are analysed separately, and they can reach different answers on the same facts without any contradiction. An extension of time may protect against damages while producing no compensation. Non-critical disruption may cost money without moving completion by a single day.
Where the record comes in
Every mechanism on this page turns on evidence: what happened, what was known and when. A record built as the job happens is worth more than any argument assembled afterwards. Construction Metric keeps that record automatically, from the messages, photographs and voice notes a site team already sends.
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Do not overread this page
These are working definitions used consistently across this site. Your contract may define some of these terms differently, and where it does, the contract wins.
General explanation of how contract mechanisms, analysis methods and legal principles generally work. It is not legal or contractual advice, not an opinion on any project, and no standard-form contract wording is reproduced anywhere on this site. Standard forms are routinely amended, so every default described here, including every time period, can be different on your project. Your executed contract, as amended, and the governing law and forum always control. Deadlines may already be running: if an event has occurred, preserve your position and take qualified advice.