Anthony B has hit the nail on the head when it comes to instrusive surveys, particularly in older buildings where critical "As Built" information and documentation is otherwise unavailable, or un-retrievable.
Intrusive surveys aren't cheap and they can cause a great deal of disruption. But there are many benefits of having a survey done.
You can often kill two or three birds with one stone by having a survey undertaken, and once completed you should not, if managed properly, have to have another survey done in future.
I often come across organisations who have spent thousands of pounds on things like asbestos and electrical surveys for all their sites, only to find for a few extra quid they could have had full structural surveys undertaken at the same time, that would inturn have picked up several other issues, which they later had to pay someone else to undertake further intrusive surveys for.
Remember that the information you get back from intrusive surveys can benefit several people in your organisation. From your risk assessor, to your estates manager, maintenance engineers, etc
Whilst doing an intrusive survey, looking at structural elements, someone else at the same time, could be looking at the electrics or mechanical services in those inaccessible areas.
Then, once the survey is complete you will have a line in the sand from which to base future assessments and plans from. You will know what is in that building, how it's been constructed , and can then manage, monitor and document what goes in thereafter, keeping an up-to-date picture of what is going on at that property.
