Notes · Design-build · Yellow Book
Errors in the Employer's Requirements
“It's a design-build contract — if the error is in our Requirements, isn't that your problem, since you did the design?” The right question for a Yellow Book. Under Sub-Clause 1.9 the test is whether an experienced contractor, exercising due care, would have discovered the error when examining the Requirements at tender. If not, it was baked into the Requirements before the Contractor picked up the pen — and it carries time, Cost, and, unusually, reasonable profit.
The right question for a Yellow Book
“It’s a design-build contract — if the error is in our Requirements, isn’t that your problem, since you did the design?” It is a fair question, and a good test of whether someone knows the Yellow Book rather than the Red. The answer turns on a single clause and a single test.
What Sub-Clause 1.9 actually says
Under Sub-Clause 1.9 (Errors in the Employer’s Requirements), if the Contractor suffers delay or incurs Cost because of an error in the Employer’s Requirements, and an experienced contractor exercising due care would not have discovered that error when examining the Requirements at tender, the Contractor is entitled to an extension of time, to Cost, and to reasonable profit. That last word matters: most FIDIC claims recover time and cost only — recovering profit is the tell of a genuine 1.9 entitlement.
The filter: discoverable at tender?
Because the Contractor designed to the Requirements, the burden carries a filter. The question is not “was there an error?” but “was it reasonably discoverable at tender?”An error a competent tenderer should have spotted is the Contractor’s own risk. The Contractor’s job is to show the error was not reasonably discoverable — that it was baked into the Requirements before anyone picked up the pen.
What that looks like on rail
On a railway it is rarely a typo. It is a flawed design criterion, an inconsistent loading gauge, or a clash in the interface requirements that only surfaces once detailed design is under way. The distinction to hold on to is this: a claim under 1.9 is nota claim for the Contractor’s own design slip. It is a claim for a defect that was in the Employer’s Requirements from the start — one no reasonable examination at tender would have caught.
A worked example
The gauge that won’t fit the tunnel
The Requirements state a rolling-stock loading gauge, a tunnel structure gauge, and the alignment’s radius and cant — each ordinary on its face. But sweep the kinematic envelope around the tightest curve, with sway at the specified cant, and it fouls the specified bore: the three criteria are mutually inconsistent. That clash shows up only in the detailed gauging analysis — a task no reasonable tender review runs — so it was not discoverable at tender. Trace it cleanly (Requirement → your compliant design → the clearance output showing the foul) and it is the Employer’s error: time, Cost and profit.
Another worked example
Continuous rail that overstresses the viaduct
The Requirements mandate continuous welded rail with breather switches to be avoided, a long continuously-articulated viaduct deck, and a design temperature range — each standard on its own. But run the track–bridge interaction analysis(UIC 774-3) and the deck’s thermal movement over that expansion length drives the rail stresses past their limits: the only cures are the expansion joints the Requirements ruled out, or a re-articulated bearing layout. That exceedance surfaces only in the detailed interaction analysis — never in a tender review — so it was not discoverable at tender. Trace it (Requirement → your compliant design → the UIC 774-3 output requiring expansion joints) and it is the Employer’s error: time, Cost and profit.
Surviving the ambiguity
“Reasonably discoverable” cannot be made precise — it is a reasonableness standard, decided on evidence. So you don’t remove the ambiguity; you win it, by moving the argument off the word reasonably and onto the record. Four moves do that:
- Raise and log tender queries. Every ambiguity you flag at tender discharges your due care and, left unanswered, shifts the risk back to the Employer. The items you queried are documented as examined; the ones no one could reasonably have queried are, by contrast, the latent ones.
- Negotiate reliance carve-outs. In the Particular Conditions, secure the right to rely on stated design criteria, interface data and the loading gauge, and list the categories deemed notreasonably discoverable at tender — geotechnical baselines, existing as-built and third-party data. The 2017 edition’s defined scrutiny period is a foothold to build on.
- Fix the benchmark. The test is the reasonable tenderer, at tender, with the tender period and the information then available — not you with completed detailed design and hindsight. Refuse the hindsight standard: show the error only reveals itself once detailed design, survey or third-party data is in hand.
- Keep the traceability clean.Maintain an unbroken line from Requirement → your design → the clash. It proves the defect originated upstream in the Requirements, and cuts off the “it’s your design slip” answer.
You designed to the Requirements — but you don’t warrant the Requirements. If the error was baked in before your pen touched paper and no reasonable tender review would have found it, the Yellow Book puts it back on the Employer: time, Cost, and reasonable profit.