What Is a Variation?
Written by James Walker · Last reviewed 15 August 2026
James Walker has 2 degrees in construction (BSc (Hons) Building Surveying · MSc Environmental Design of Buildings) and an extensive background in issue resolution, resolving over £4 billion of consumer issues.
A variation is a change to the work that was originally agreed, something added, removed or altered, which is priced separately from the original quote.
Why variations cause so many disputes
Because they are usually agreed verbally, in passing, on site, and then argued about at the end.
A homeowner asks for an extra socket. The builder does it. Neither discusses the price. Six weeks later a final invoice arrives with a figure attached, and there is nothing written down to compare it against.
Multiply that by twenty small changes across a long project and you have the single most common cause of a disputed final bill.
How they should be handled
Each variation described in writing, priced before the work is done, and confirmed by both parties. An email exchange is enough, it does not need to be formal.
The original agreement should set out how variations are priced. That clause costs nothing to include and saves a great deal.
Unforeseen work
Some variations are not choices. Rot found under a floor, foundations needing more depth, pipework that must be replaced. These are genuine and reasonably chargeable, but the same rule applies: described, priced, agreed, then done.
How it works
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