If you're worried about how the language will be interpreted, then ask the other party how they intend to handle the repairs. If you're not happy with their answer, then add an addendum to the contract to spell out exactly what you'd like to have done.
With it being so vague, you won't have a leg to stand on if you want to hold them to how it's orginally written, since "finished" has many different definitions as you had mentioned, it just depends on who you're talking to.