A variation is work that was not part of the original contract sum and is added during the build, so it is valued and charged separately. The reverse is an omission: work taken out of the contract and credited back.
Where variations come from
- Client changes — a different layout, more expensive tiles, an extra socket
- Unforeseen conditions — asbestos under the floor, a foundation weaker than assumed, a rotten joist only visible once you strip out
- An incomplete specification — what is not described is not in the price. In practice this is the largest source of argument
- Third party requirements — an additional condition from the local authority or a utility provider
How to keep control of it
Under most standard forms of contract the client can instruct a variation, and the contractor is entitled to have it valued. What almost every dispute comes down to is not the entitlement but the evidence: what exactly was instructed, when, and at what price.
- Agree it before the work is done. Description, price and effect on the programme. An email saying “go ahead” is already worth a great deal
- Ask for a price, not an indication. “We’ll sort that out later” is the most expensive sentence on a building site
- Value omissions too. Work taken out should come off the account just as readily as work added goes on
- Hold a contingency. On alterations to an existing building, 10 to 15 per cent of the contract sum is a realistic reserve
- Attack the cause. A complete specification and a drawing that shows everything is the cheapest insurance against variations there is
- Keep one running list. Number each variation and carry a running total, so the final account holds no surprises
Related terms
- Omissions
- Building costs
- Specification
- Contractor
- Contract
- Terms and conditions
- Construction management
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