Water-damaged walls can be hard to notice, primarily since they work from the inside out, and water seeps through from behind the wall. Also, sometimes, water can leak from the middle of the wall out into the front. So, when doing the repairs, you must be aware of the source or cause of the leakage. That is, you must know where water is leaking.
A few common signs that you may have water-damaged walls include bubbling, staining, or sagging in and around the area. So, check for any leakages or water-damaged walls or surfaces, especially if you notice these signs.