Variation
A change to the scope of works under a construction contract. Standard forms typically provide mechanisms for valuing variations and adjusting the contract sum and completion date.
Independent editorial summary — not the official statute text. Read the official version on legislation.gov.uk.
A variation is a change instructed to the scope, specification or sequence of works under an existing construction contract, rather than a separate new contract. Standard forms such as JCT contracts typically empower the contract administrator or architect to issue instructions varying the works, with built-in machinery for valuing the resulting change and, where necessary, adjusting the completion date. The Technology and Construction Court decision in Hallamshire Construction plc v South Holland District Council [2004] EWHC 8 (TCC) illustrates this in practice: additional 'phase 2' works were 'added to the existing contract by means of a variation issued under that contract', implemented through an Architect's Instruction, rather than requiring the parties to negotiate an entirely new contract for the extra work.
Because a variation is issued under the existing contract, its cost is usually dealt with through the contract's own valuation machinery rather than open-ended negotiation. In Hallamshire, the variation instruction itself specified that 'all costs in connection with this variation to be agreed at fair and reasonable costs' by the parties' quantity surveyor, and the court held that this phrase meant individual rates in the bills of quantities would be agreed item by item using the JCT contract's established processes for pricing omissions, specification changes and rate changes — not as a single lump-sum package outside the contract.
The Hallamshire case also shows the practical importance of distinguishing a true variation from a fresh, free-standing contract: the contractor argued the additional works had never been the subject of any binding contract at all, while the employer argued the instruction took effect as a variation under the original agreement, so that the extra works were extra or additional work performed under, and priced by reference to, that same contract. The court's conclusion — that the arbitrator had correctly found the instruction to be an agreed variation to the existing contract, not a new stand-alone bargain — turned on the parties' negotiated acceptance of the specific terms of the variation instruction.
Example
A client who instructs the contractor, part way through a build, to substitute a more expensive type of external cladding is issuing a variation; the contract's valuation rules (rather than a fresh negotiation from scratch) determine how much extra the client must pay and whether the completion date should be extended.
Related terms
Official sources
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