Guide · 5 min read
What is a variation in construction?
A plain-English guide for UK builders: what counts as a variation, what usually doesn't, and why the paperwork matters.
The short answer
A variation is a change to the agreed scope, price or programme of a building contract. It changes what the client has agreed to pay for, or when the work is done. Adding work, removing work, changing materials and moving the programme are all variations.
Common types of variation
- Addition: work that is not in the original scope, such as an extra socket or a larger window.
- Omission: work that is removed from the scope and no longer needs doing.
- Substitution: a different material or specification from the one priced.
- Change of sequence or programme: work moved to a different time, or extra time needed on site.
- Unforeseen conditions: problems found once work starts, such as a drain run under a slab. Whether these count as variations depends on your contract.
What usually isn't a variation
- Correcting your own defective work, which you normally do at your cost.
- Small adjustments that fall within the agreed scope.
- Work the client has already accepted in the original price.
Check your contract, because the exact definitions vary.
Why the paperwork matters
Most building contracts expect variations to be instructed in writing and valued. Without a written instruction, you may have to prove both the work and its cost after it is done. Clients and builders often disagree about whether something was agreed. A dated record settles that question quickly.
How contracts handle variations
Standard building contracts, including the JCT forms, have a variations clause. It sets out how instructions are given, how the work is valued and the time limits for giving notice. The rules differ between contracts, so read the clause in the contract you actually use.
This page is general information, not legal advice.
Related guides
- Variation guideHow to stop extra work going unpriced, unsigned and unbilled. A practical guide for UK builders and remodellers.
- Pricing a variationHow to price extra work for a UK building job: rate cards, the programme effect, overheads and a worked example.
- Extra work on siteA six-step checklist for UK builders when a client asks for extra work on site: pause, price, get it signed, then start.
- Variation or change orderVariation or change order: what the terms mean in UK building contracts, what matters more than the name, and how to record every change.
- Avoiding unpaid extrasFive habits that stop unpaid extras on a building job: site logs, photos, same-day pricing, written confirmation and billing in every application.