My bathroom wall tiles are in very sound condition but ugly colour. To save on cost I'd like to install PVC panels over, however due to the age of my home I can't say for absolute certain how good the waterproof membrane would have been. I know the PVC panels can be applied directly over tiles but there's no mention (that I can find) of applying a waterproof layer first. To be totally safe I'd like to apply a new membrane over the old tiles before installing the PVC panels. Are you able to provide any advise about what I'm considering doing please ?