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Construction Law/Approval for Shop Drawings


Dear Sir,
I am working   as  a Consultant QS in a Engineering  firm.  Our contract is based on FIDIC  Red Book(1999).   In the Shop Drawings for plumbing work contractor has indicated wrong diameter  ( different to Contract drawing ) and  Engineer has approved the same without noticing  the change. Later at  site Engineer found the mistake and asked  to carry out the work as per the Contract drawings. But contractor calim additional Cost and time since the Engineer already approved the shop drawings.  Can the contractor    claim for additional money and time?

Your   kind respond is highly appreciated.

Thank you,

Ruawan Kumara

Dear Ruawan,

Thank you for this question.

The answer you seek will depend upon what the purpose of the shop drawings is under your contract and the status they have. Usually shop drawings are intended only as a mechanism for  the contractor to explain its working arrangements and to show minor detailing. They are not intended to supersede or otherwise change any design detail. Indeed under the FIDIC 1999 Red Book contract the Contractor does not have authority to make any change unilaterally. As such, approval by the Engineer does not relieve the Contractor from complying with its obligations under the Contract, including constructing to designs.

The second scenario is where the designs are incomplete and the requirement shop drawings is to "fill in the gaps", then information given on the shop drawings may carry more weight and importance. This is where you contract should define the exact purpose.

If the analysis in my first paragraph is correct, the Contractor has produced work that is not in accordance with the specification/contract and can be required to correct its mistake at its own cost. The fact that the Engineer approved the shop drawings does not detract from the Contractor's responsibility and liability.

If, however, the analysis follows my second paragraph then, subject to the precise wording of the contract (which I have not seen) the Engineer was approving the Contractor's designs and the Contractor has a much stronger argument.

I hope that this assists you.

Kind regards,
John Dowse

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John Dowse


Legal; contract interpretation; quantum; delay analysis. Practitioner in arbitration, adjudication and mediation.


Thirty-three (33) years experience in building and construction, at all levels both within contracting and consulting organisations. Practising arbitrator, adjudicator, and mediator. Faculty approved trainer for the Chartered Institute of Arbitrators. Lecturer on construction contract forms and dispute resolution practices.

Chartered Institution of Civil Engineering Surveyors Chartered Institute of Arbitrators Institute of Directors Society of Construction Arbitrators

Various UK and International construction and legal publications.

LLB (Hons), Pg Dip (Legal Practice), MCInstCES MCIArb MIOD Barrister

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