Walk the floor slowly and mark what changes under load
Clear loose rugs and ordinary clutter, then walk the route in normal footwear while another person observes where possible. Use removable tape to mark squeaks, deflection, raised edges and changes between rooms. Note whether movement happens beside a wall, at a board end, near a radiator pipe or only under heavy furniture. A spirit level can describe slope but does not diagnose the cause, and an old floor does not need to be perfectly flat to function well. Record the pattern with photographs and a short video rather than jumping on the area repeatedly. If movement is broad, worsening or accompanied by cracking, distortion or damp, stop at documentation and seek appropriate building advice. A localised loose trim needs a different response from movement in the supporting structure.

