We've just had our bathroom updated and the joists under the bath needed to be replaced (I'm not surprised and did tell the guy this also!). Anyway, he's charging us for unforeseen work and I can't work out what is fair. Normally you'd just pay what they're asking for but he's included stuff on his list that a) was in the quote and b) one was his cock up so I expect him to fix it properly anyway.
How do I work out what's fair to pay for the replacement of damaged joists??