sub-floor

The hallway subfloor seems to get damp, especially if it's been raining heavily outside. Do you think it would be a sensible solution to apply slurry to this floor, and the walls below the floorboard level to prevent this? I don't want to make a mistake before putting the floorboards back down...

Hi All, I am doing a kitchen extension. 3m X 6m, and like to install wet ufh. need help to decide the best way to prepare my concrete subfloor for wet ufh. option 1: mot + sand blinding + dpm + kingspan + dpm+ concrete + ufh boards (18mm) + ufh pipes + screed + tiles option 2: mot + sand...