Variation in construction

In practice for trades

Most contracts give the client a right to instruct variations and give the contractor a right to be paid for them. The problem is almost never entitlement. It is evidence. A variation asked for verbally on site, done the same afternoon and never written down is the single most common way trades give work away for free.

Valuation normally follows a hierarchy. Rates in the contract are used where the work is similar, adjusted rates where it is comparable but not identical, and a fair valuation or day works where there is nothing to compare it to. Day works pay for time and materials but need signed sheets at the time, not reconstructed later.

The discipline that fixes this is boring and it works. Confirm every instruction in writing before starting, with the price if you have it and a note that the price is to follow if you do not. A one line message sent the same day is enough to make it a variation rather than an argument at final account.

Worked example

A bathroom contract at £8,000. The client asks to move the soil pipe, which is not in the original scope. Priced at £640 of labour and £185 of materials, the variation adds £825, taking the account to £8,825. Confirmed by message before the wall came down, it is a straightforward line in the final account.