Variation orders,
and the variations nobody instructed.

A variation order is an instruction to change the work under a construction contract: to add to it, omit it or change how it is done. The standard forms call it an instruction. Under the JCT Standard Building Contract, an instructed variation is valued only if it was instructed in writing, confirmed in writing afterwards or sanctioned later. Extra work done on a nod, with none of those, is the variation most often argued over at final account.

What is a variation in construction?

The JCT Standard Building Contract defines a variation in clause 5.1. It covers two kinds of change:

• Changes to the work itself: an alteration of the design, quality or quantity of the works. That includes adding, omitting or substituting work, changing the kind or standard of materials, and removing work already done.
• Changes to how the work is done: new obligations or restrictions from the employer on access, working space, working hours or the order of work.

The contractor can make a reasonable objection to the second kind. The first kind it must normally carry out once properly instructed, with narrow exceptions such as a quotation still pending.

Variation order, instruction or change order

“Variation order” is the everyday name on site, but none of the main UK standard forms uses it as a defined term. Each has its own:

The name matters less than the person. On the JCT Standard Building, Intermediate and Minor Works contracts, only the architect or contract administrator can instruct a variation. Under JCT Design and Build, the employer instructs. JCT’s guidance on the Minor Works contract is plain that the employer cannot. A client who asks the foreman for an extra socket has not given an instruction under the contract.

Instructions given on site

JCT requires instructions in writing. An instruction given any other way, on a site walk or over the phone, has no immediate effect under the Standard Building Contract. Clause 3.12 sets out what happens next:

• The contractor confirms it in writing within 7 days. If the architect does not dissent within 7 days of receiving that confirmation, the instruction takes effect.
• The architect can confirm it in writing within that period instead.
• Where nobody confirms it but the work is done, the architect may still confirm it at any time before the Final Certificate, with retrospective effect.

Clause 3.14.4 adds a further route. The architect may sanction in writing a variation the contractor made without any instruction. The Minor Works contract is stricter: an oral instruction has no effect until the architect confirms it in writing, and there is no route for the contractor to confirm it.

Writing does not have to mean a formal form. In Vainker v Marbank in 2024, on an amended JCT contract, the court held that only variations instructed in writing or confirmed under clause 3.12 are valued. It also said an email or the issue of a drawing may be enough writing.

On a JCT job the instruction given on the slab is worth seven days. After that it is worth whatever the architect decides to confirm.

How a variation is valued

Under the Standard Building Contract, the valuation rules in clauses 5.6 to 5.10 apply in order:

• Work of similar character to work in the contract is valued at the contract rates, with a fair allowance for changed conditions or a significant change in quantity.
• Work not of similar character is valued at fair rates and prices.
• Work that cannot be measured is valued as daywork: prime cost plus the percentage additions in the contract. Daywork vouchers go in within 7 business days of the work.
• Other work affected by a substantial change in conditions is treated as varied too. Anything left is given a fair valuation.

A variation can also be priced before it is done. Under clause 5.3 and Schedule 2, the contractor can be asked for a Variation Quotation. The work then waits for a Confirmed Acceptance or a further instruction. The contractor can decline to quote within 7 days. On the Minor Works contract, the parties try to agree a price before the work starts. Failing that, it is valued on a fair and reasonable basis.

Signed daywork sheets carry most of the weight on small variations. Daywork sheets: getting them signed and paid covers what one needs.

Variations under NEC4

NEC4 has no variations as such. A Project Manager’s instruction that changes the Scope is a compensation event under clause 60.1(1). The Project Manager should notify it, since it is their own instruction.

For events the contractor has to notify, clause 61.3 sets a time bar. Notice must be given within eight weeks of becoming aware of the event, or the entitlement is lost. Under the NEC4 subcontract it is seven weeks. The time bar does not apply to events that arise from the Project Manager or Supervisor giving an instruction or notification, issuing a certificate or changing an earlier decision. A compensation event is assessed on Defined Cost plus the Fee.

The variations nobody instructed

Most disputed variations were never refused. They were agreed on site, done in good faith and never written down. By final account the person who agreed them has left, and the architect will confirm only what the file supports.

Two decisions explain why the courts rarely help. In Rock Advertising in 2018, not a construction case, the Supreme Court enforced a clause requiring changes to the contract itself to be in writing. Estoppel was left as a narrow safeguard. In Obrascon in 2014, a contractual notice requirement was treated as a condition precedent to the claim, though read reasonably broadly. The court will enforce the procedure the contract sets out.

The fix happens on site, the same day. Confirm every instruction in writing, to the person with authority to give it, before the work starts where possible. An email naming the instruction, the date and who gave it is enough to start the clock under clause 3.12. A photograph of the work before and after helps value it.

Getting a variation paid

Once a variation is in an application for payment, it follows the Construction Act like any other sum. It is paid if it survives the payer’s payment notice or, where no payment notice is served, a valid pay less notice. A variation the contract does not recognise can still be challenged on its merits, so the instruction behind it needs to be on file.

Getting paid for variations you were told to get on with covers the evidence that stands up when the instruction was verbal. Pay less notices covers the deadlines.

Clause numbers in this article are from the JCT Standard Building Contract and Minor Works Building Contract 2016. The 2024 editions keep the same headings, and many contracts are amended. Read the contract on the job. This is general guidance rather than legal advice.