extra charges after job is completed

[GregTheStopSign]

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??

[GregTheStopSign]

Bump

[MrsTaraPlumbing]

Contact the builder to point out these things.
If it was included in the quote you shouldn't pay twice.

[GregTheStopSign]

Thanks Tara, I don't plan to pay twice!

He is a friend of a friend and has done an average job but it's more that I want to be sure I'm being fair as I really don't want to pay him another penny, so my judgement might be out