The builder says it is an extra. Do I have to pay for it?

Some extras are real: you changed your mind, the drawings moved, the ground surprised everyone. But whether something is an extra is decided by the contract and the priced quote, not by the sentence 'that will be extra' - if the work was already included in what was priced, it is not extra at all, and a generous allowance elsewhere is not a licence to re-price included work. So the response is always the same, delivered politely: show me. Which drawing changed, which item was excluded, where the quote says this was never allowed for. If it is genuinely extra, the second rule lands: the price in writing before the work is built, because an extra priced first is a decision and an extra priced afterwards is a bill. The free Is It A Variation? decision tree walks the question step by step.