Due diligence will only go so far, though. Last time we bought, our surveyor was clear that there were parts of the property they would not be able to inspect, and obviously they could not give any assessment of the state of those parts. For example, they weren't allowed to move the seller's furniture to check underneath or behind it, and naturally there would be structures and services that couldn't be inspected without taking floors up or the like. We have since identified several significant defects that were missed as a result of those limitations, but there is nothing either we or our surveyor could realistically have done to anticipate them given there were no visible warning signs in accessible areas.