How to fix a scraping door
Step 1 - Assess the cause of the scraping
Have a look around the door. The house may have moved slightly and the door is no longer square to frame or floor. This is seen as a gap that is wider at bottom than at top or vice versa. First, check all screws holding hinges are secure. If not, tighten.
If you can’t get a screw to bite, remove the screw and fill the hole with glue and a matchstick, then drive the in screw again. If the door still scrapes the floor, run utility knife around bottom hinge to cut paint film.
Step 2 - Undo screws
Now it's time to start undoing screws. If they have been painted over many times, place the screwdriver in the screw slot and tap with a hammer. This will loosen the screws and ensure that screwdriver blade can get proper purchase.
Step 3 - Place cardboard shim behind the hinge
Pull the hinge away from the door frame and place 1mm shim of cardboard or timber to fit behind hinge. Screw the hinge back and check door operation. It should have lifted the closing bottom edge slightly. If the door still scrapes the floor, try a second shim. This should fix it. If the door is still scraping badly, you may actually need to take the door off and plane the bottom edge, but it’s always worth giving this simple fix a go first.