Baseline vs update: find what really moved

Updates hide drift. Comparing two programmes properly — finish, duration, float, logic, effort and cost variance — and turning what moved into attribution rather than argument.

Schedule · 5 min read · updated 2026-06-12 · FIDIC 2017 Red Book references unless stated

1. Drift hides inside updates

No single update looks alarming. Ten activities re-sequenced here, a calendar tweak there, a constraint added to hold a date — and six months later the completion forecast is intact while the network underneath has quietly changed shape. By the time the finish date finally moves, the causes are buried several updates deep.

Routine comparison — every update against the last, and against the baseline — is how you catch the drift while it is still attributable.

2. Compare the right pair, for the right question

Baseline vs current answers the contractual question: how far from the promise are we, and where? Update n-1 vs n answers the management question: what changed this period, and was it progress or re-planning? Both comparisons matter, and they routinely disagree — a re-sequenced network can hold the finish date while consuming the float that the next event will need.

In ControlsIQ

Schedule Comparison diagnoses any two uploaded programmes — variance on finish dates, durations, float, effort, cost and predecessors — so re-planning is visible separately from genuine progress.

3. Read the variance set as evidence

Finish-date variance is the headline, but the others carry the story: duration changes show re-estimation; float changes show consumption or release of buffer; predecessor changes show re-sequencing (and are where added constraints and broken logic hide); effort and cost variance show scope movement masquerading as progress.

A change you cannot explain is a finding. Either the update contains an error, or something happened on the project that has not yet been logged as an event.

In ControlsIQ

Each comparison is exportable for the period record — the contemporaneous evidence trail that delay analysis and EOT submissions later rely on.

4. From drift to attribution

The discipline that makes comparisons valuable at claim time: when a comparison surfaces movement, tie it to its cause now — an instruction, a late approval, a subcontractor failure, weather — and where the cause is an event giving entitlement, log it and start the notice clock. Attribution recorded at the data date is worth more than any reconstruction.

In ControlsIQ

Log the causal event in Notice Tracker as soon as the comparison surfaces it — the awareness date is then contemporaneous, and Delay Analysis can later correlate the event to the window where the path moved.

Run this workflow — free See the platform

Educational content for construction professionals. This guide summarises common contract mechanics and industry practice; it is not legal advice, and contract forms differ — your contract’s wording, including its Particular Conditions, governs. ControlsIQ outputs are designed to support professional judgement, not replace it.