There are several signs you may have foundation problems. If your foundation is visible (you have a basement or crawlspace foundation) there will be visible evidence of cracking or crumbling. If your walls are warped, or the floor slopes, those are major indicators you foundation is sinking. If doors are hard to open or close, or get stuck, this may be a foundation problem (but could also just be a door frame issue, so don’t freak out yet). Cracks on the walls or on floor tiles are a sign. Water in the basement or crawlspace can be a definite danger sign. Warped walls or gaps between the walls and ceiling should be cause for concern. Having any of these symptoms (outside of the blatant visual evidence of a cracked or crumbling foundation) might be a warning sign, but is not necessarily proof of foundation problems. However, if you do have symptoms, you would be wise to have an inspection done. Problems like that only get worse.