If everything you can see, in the way of structure, is dry, that’s a pretty good sign that the water proofing system is in good shape. Look particularly in unfinished spaces where you can see the wall structure. You may have to open up some areas. Look in areas where ext. grading doesn’t provide good drainage away from the bldg. If there are places with interior water problems that’s where you should spend your time. And, that ext. water proofing must be fixed. Be very careful with a jack-knife, the blade has a nasty habit of closing on your fingers which are around the handle. Use an ice pick or a long slender, small blade, screwdriver, or some such, instead. Test the wood for soundness particularly if there have been water problems, dry wood vs. stained wood. Is the wood sound, is the appropriate wood treated to the correct spec. for PWF’s, is the lower level dry? Are there any inward bulges in the bsmt. walls, a sign of a failed stud. Carpenters have a habit of forgetting that the inner edge of the studs is in tension and knots, etc. should be avoided on this edge, just like the bottom edge of a fl. jst. Check the connections, hardware and blocking at the top of the wall and to the fl. diaphragm, for adequacy and any movement. Does the wall have good support at the bsmt. fl. slab? That’s about it, after all it has stood for 15 years already, and is still dry.