What about the 18 yr old grandson helping out with the washing? And his parents? They should be helping too!! Why should you do the work - he overstepped boundaries and should know that he has to compensate for his neglecting to protect what he must have known what is valuable to you for the trust and privilege of using your house. He is responsible if he's 18 and should be held accountable. I'd contact every one of his friends too and let them know they overstepped it and that you expect them to help too.