The instructed variation is the easy case. The dispute is about work that changed without an instruction, and about what a hundred small changes did together.
Instructed change, and constructive change.
An instructed variation is valued under the contract's own machinery: contract rates where the work is of similar character, pro-rata rates where it is not, fair valuation where neither applies.
Constructive change is the harder argument. Work performed differently because of an employer act, a late release of information, or a changed condition, without any instruction ever issued. It has to be proved as a change before it can be valued as one.
Cumulative impact is separate again. Individually minor changes can combine to alter the character of the work, and that claim is quantified as disruption rather than as the sum of the individual valuations.
Formal requirements matter. Where the contract requires written instruction, conduct and course of dealing become the battleground.
How a change is established and valued.
Establishing the change and valuing it are two separate exercises.
Identify the scope baseline
Fix what the contract required before any change is alleged.
Locate the change
Find the instruction, or the act relied on as constructive change.
Test authority
Confirm the person instructing had power to bind, and that any formality was met.
Value under the machinery
Apply contract rates, pro-rata rates, or fair valuation in the contract's order.
Trace the time effect
Follow the change through to the schedule, not only to the account.
Assess cumulative impact
Consider whether the changes together altered the character of the work.
What the argument is built from.
Constructive change is proved from the ordinary record of the work.
Where these claims fail.
Change claims collapse in valuation more often than in principle.
The baseline was never fixed
Without a clear statement of the original obligation there is nothing to measure the change against.
Constructive change is asserted, not proved
Doing the work differently is not a change until the employer act that caused it is identified.
Formality is ignored
Where written instruction is required, oral direction has to be pleaded as waiver or estoppel, not as compliance.
Cumulative impact is double counted
Claiming the individual valuations and a cumulative disruption sum for the same work invites the whole claim to be rejected.
What the Matter Model does with it.
It follows every change order and its pricing through to the schedule effect and the cost effect, and keeps both tied to the instruction or the act relied on.
Where a change is claimed as constructive, it holds the claim against the specific employer act said to have caused it, or marks it as unproven.
Standards and authorities
- Standard form variation and valuation provisions (FIDIC, NEC, JCT)
- SCL Delay and Disruption Protocol, 2nd edition (February 2017)
General reference on how these disputes are argued. Not legal advice, and not a statement of the law of every jurisdiction or seat.
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