Plain-language explanations of key terms — for engineers and project managers, not lawyers.
A change to the scope, specification, or conditions of the works instructed by the Engineer (or Employer's Representative) under the contract. FIDIC Clause 13 sets out the variation procedure: the Engineer may instruct variations and the contractor must carry them out. Variations are valued at contract rates where applicable, or at fair rates where not. The contractor is entitled to an extension of time for variations that affect the critical path. Variations not covered by the contract may be the subject of a claim.
The process of determining the value of work, whether for the purpose of interim payments, variations, or final account. Under FIDIC Red Book, valuation of variations and remeasured work is done by reference to the Schedule of Rates and Prices. Where these are not applicable, the Engineer and contractor agree a fair valuation, or the Engineer determines a fair value. Good valuation practice requires detailed records, agreed procedures, and timely agreement.