What counts as a variation
Under JCT, a variation (in Design and Build, a “change”) is a change to the design, quality or quantity of the works, or to obligations or restrictions such as access, working hours or sequence. Under NEC4, an instruction changing the Scope is a compensation event. Work the contractor was always required to do isn’t a variation, so read the specification and contract terms first.
Instruct it properly
- Only the person named in the contract (architect/contract administrator, employer’s agent or project manager) can instruct variations.
- Instructions should be in writing. If you receive one orally, confirm it in writing straight away.
- Ask for a quotation or agree a price before work starts where possible.
How variations are valued
JCT uses valuation rules: contract rates where the work is similar, adjusted rates where conditions differ, then fair rates, or daywork where appropriate, unless a quotation was accepted. NEC4 assesses compensation events by their effect on Defined Cost plus the fee, using quotations. Variations can also affect time: claim an extension of time if they delay completion.
Homeowners and extras
On home projects, unagreed “extras” are a top cause of disputes. Agree every change in writing, with a price, before it’s done. See homeowners and builders.
General information, not legal advice. What applies to you depends on your contract, the facts and where the work is, and the law changes. Check the sources below and take advice from a qualified professional before acting on anything that matters.
Last updated: 6 October 2026
