Things You'll Need
Drill with screw tip
Treated deck screws, 3 inches long
A threshold is the sill plate located under most exterior entrance doors, between the jambs. Some thresholds have height adjustment screws that allow the weatherstrip atop the threshold to be raised, or lowered to meet the bottom edge of the door. When replacing thresholds, it is important to check that the replacement part is the same thickness, or height, as the original to maintain weatherproofing and prevent obstructing the door.
Remove the rubber gasket on top of the threshold to reveal the adjustment and mounting screws. Locate the mounting screws. These are set in recessed holes, lower than the adjustment screws, and spaced evenly along the threshold. There are typically three or four.
Remove the mounting screws with a cordless drill and screw tip, turning them counterclockwise to twist them out. Cut along the edges of the threshold with a utility knife to cut any old caulking between the threshold and the floor.
Pry the threshold from the door frame with a large pry bar, starting by lifting one end of the threshold up and tilting it out of the frame. Scrape away any old caulking from under the threshold with a paint scraper, and sweep the installation area to remove debris.
Position the old threshold on top of the replacement, and trace the end profile of the original onto the new threshold. Cut the ends of the new threshold to match the original, using a reciprocating saw. Apply a quarter-inch bead of silicone caulk along the outside edge on the bottom of the threshold. Fit it into the door jamb and tap it down to the floor. Remove the rubber gasket on top of the new threshold.
Install a 3-inch treated deck screw through each of the mounting screw holes in the threshold. Use a screwdriver to adjust the height adjustment screws until the top of the threshold is one-eighth of an inch below the bottom of the door. Replace the rubber gasket on top of the threshold so it presses against the bottom of the door.