Damp proofing companies install a product. The individuals who perform such tasks have been trained in that particular task and nothing else.
To conduct an accurate survey from which a report proposing works to rectify the causation requires the ability to draw a correlation between factors that can only be obtained from hands-on experience. There is a world of difference between confirming damp and suggesting a solution and locating the source of ingress and proposing works which will ensure a complete and indefinite cessation. It takes about twenty years to have experience from groundwork upwards to roofing, to have complete awareness of materials and knowledge of construction. Without that practical experience, it doesn’t matter what your Protimeter says, or what your qualifications say you are, in actuality you’re only guessing at what’s causing the damp. There are many get-out clauses in the damp industry, that’s why it attracts so many crooks, amateurs or those who are unconcerned whether their treatment works or not. Twenty years is a long time, I can’t think of many other professions that require that level of experience.
Below: Close to Chatham Station, these properties are of some historical significance; most notably due to a Dickens connection with a property further along. The damp in this instance was caused by a roofing issue.