A variation is any change to the originally agreed scope of work, whether it's additional work, work that's been omitted, or a change to what was specified. Variations are a normal part of renovation — no project of any size runs exactly as planned. What matters is how they're managed.
of UK homeowners who used a builder had to pay unexpected costs that arose during the project. Many of these were legitimate variations. Some were not.
The difference between a legitimate variation and a scope dispute
A legitimate variation arises when work is genuinely beyond what was agreed — either because something unexpected was discovered (hidden structural issues, outdated wiring behind a wall) or because the homeowner changed their mind about something after the contract was signed.
A scope dispute arises when a builder claims something is additional work, but the homeowner believes it was included in the original price. These disputes almost always trace back to the same source: ambiguity in the original scope of work.
The prevention is always better than the cure: Every legitimate variation and every scope dispute is the consequence of something that wasn't clearly defined before work started. The more precise the original specification, the fewer variations arise — and the easier the legitimate ones are to identify.
What to do when a variation is submitted
First, pause. Don't agree to anything verbally or via an informal message. A variation submitted under time pressure on site is still a change to a legal contract, and agreeing to it without understanding it fully is how costs spiral.
The questions to ask before approving any variation:
- Is the additional work clearly described in writing?
- Is there a written cost estimate showing how the price was arrived at?
- Is the work genuinely outside the original scope, or was it implicit in what was agreed?
- Does the work need to happen now, or can it be deferred until the cost is properly understood?
- What happens to the programme (timeline) if this work proceeds — or if it doesn't?
How to respond to a variation you're not sure about
You are entitled to query any variation before approving it. A reasonable response is to ask the builder to provide, in writing: a description of the issue, why they believe it falls outside the original scope, how they arrived at the cost, and how long it will take to carry out.
If you have a contract, refer to the variation clause. Most standard contracts (including the JCT Minor Works form) require variations to be authorised in writing by the client before the builder proceeds. If your builder has done additional work without written authorisation, their entitlement to payment may be limited — though this depends on the specific contract terms.
When a variation is clearly legitimate
Not all variation claims should be challenged. When a builder opens a wall and finds asbestos, or discovers that the original drainage run is in a different location than the drawings showed, the cost of dealing with that is genuinely additional. Arguing against legitimate variations damages the working relationship and rarely produces a fair outcome.
The discipline is knowing the difference — and that comes from understanding what was in the original scope well enough to assess whether something falls outside it.
Building a system before work starts
The homeowners who handle variations best are the ones who established a clear process before work started. Specifically:
- All variations must be submitted in writing before work proceeds
- Each variation must include a cost estimate and a programme impact assessment
- No variation proceeds without written client approval
- A running variation log is maintained by the builder and shared with the client
This doesn't require a formal project management system. It requires a shared understanding, established at the start, that this is how changes will be handled. Most builders will agree to this — and the good ones will suggest it themselves.
If you believe a variation claim is unfair
If you dispute a variation claim, raise it in writing with the builder as soon as possible. Explain which element of the original scope you believe covered the work in question. Give the builder an opportunity to respond.
If the dispute cannot be resolved directly, the JCT contract provides for adjudication — a relatively quick and inexpensive process compared to litigation. The Technology and Construction Court (TCC) handles more serious construction disputes. The Federation of Master Builders also offers a dispute resolution service for projects involving FMB members.
In most cases, a clear written record of what was agreed, combined with a calm and factual approach to the dispute, is enough to reach a resolution without formal proceedings.
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