We have tenants that have carved holes on the drywall to access the heat pipes and AC mains. At some point they will patch the drywall very well. Perhaps by another piece of drywall that closely fits the hole and all that had to be done is paint it over and it will be as if nothing had been tampered.
So I need a way to detect any discontinuity on the drywall piece (sort of like a stud finder) if such a technique exists.
Of course, I can simply find where the AC mains and heat pipes run through and then sand the wall right in front of them and viola, I've found the patch. But, I was wondering if such a technique exists.
Best Answer
You can try a magnet. They will have to secure any substantial patch with a nail or screw. But really there is no exact way to know what was the patch and what was existing drywall, because the existing drywall will also have screws/nails around it.
So either the patching will be in a unique shape and you can find it or it isn't and you need to take pictures of the wall before they patch.
Real world I seriously doubt this will be patched absolutely perfect. Not only would they have to do a superb job with the drywall and mud but they would also have to prime it and paint it feathered in with the existing area. So in reality a high powered light and a good angle on the wall and you shouldn't have a problem.