Get the price before the change is built

Every change - a variation, in contract language - has its cheapest moment exactly once: before the work is done. Priced in writing first, it is a decision you make with a number in front of you; built first and priced later, it is a bill you receive, at a number the builder chose, with the work already in the wall behind it. The rule survives politeness: however small the change, however good the relationship, the sentence is always the same - happy to go ahead once we have the price in writing. A builder who resists that sentence is telling you something worth knowing.