How about suggesting that the person pay for a destructive test to
confirm the wall is actually damp, rather than go through the whole:

These might be of use if there is reason to believe there is a damp
problem, but doing one simply because a surveyor wants to offload
responsibility and a salesman says they want to do some work
isnt appropriate imho. Unless theres a realistic reason to believe
otherwise, the problem normally isnt damp, its the damp game.


NT