Quick answer

Yes but rarely in the United Kingdom: a change so peculiar and different from what the parties contemplated may fall outside the variations clause and amount to a separate contract to be paid on a quantum meruit or fair valuation, but a mere increase in quantities will not, and the English courts are cautious about finding one

Yes, but rarely in the United Kingdom. A change so peculiar, so unexpected and so different from what the parties reckoned on may fall outside the variations clause and amount to a separate contract, to be paid on a quantum meruit or fair valuation rather than at contract rates. In Thorn v Mayor and Commonalty of London the court accepted that such work may fall outside the contract altogether, while a mere increase in quantities, even a substantial one, will not invalidate the contract. Bush v Whitehaven Trustees shows a job forced by employer delay into harder winter conditions paid on a quantum meruit, and in Blue Circle Industries v Holland Dredging Co a variation directing that excavated material form a bird island was held to be work wholly outside the dredging contract and so a separate contract. The English courts are cautious, and in McAlpine Humberoak Ltd v McDermott International the Court of Appeal overturned a finding of a separate contract despite a large rise in drawings and a cut in the number of pallets.