We had an extension and moved the toilet. The old pipes to the sewer were not capped off properly. We now have rats in the house / cavity walls to 4 properties. We have had a camera survey that identified the problem. It will cost £900 to get it sorted. Is the builder liable? If yes, how do I go about getting them to pay up... They no longer answer emails of calls of course, not about this but a few snagging issues. Another option is insurance. Or do we have to just pay ourselves. I feel like the builders should pay but making it happen with be a pita and obviously we want it done sooner rather than later.