If your door threshold is badly deteriorated, it may need to be completely removed and replaced before adding any new weatherizing effects to the doorway.
1. Check the clearance between the door and the trim pieces (such as the door stop) and remove if necessary.
2. Swing the door open as far as it will go. If necessary, carefully pry the trim loose with a prybar and a wooden wedge so as not to damage either the trim or the frame.
3. You may need to use a circular saw or chisel to cut through the threshold to remove it from the doorway. Take great care in this step so as not to cause any damage to the interior floor and other trim.
4. Measure and cut the new wooden threshold to the proper length so that it will fit snugly.
5. Notch the threshold to fit properly around the stops.
6. After thoroughly cleaning the old material and dirt out of the doorway, spread a good amount of caulk on the bottom. This will assure an airtight seal in that joint between the floor and the threshold.
7. Tap the new threshold gently into place with your hammer.
8. Drill some pilot holes slightly smaller than the finishing nails you will use to secure the threshold. Then nail the threshold into its permanent position.
9. Countersink the nails with a nailset and fill the holes with wood dough. Sand lightly when dry.
10. Apply a stain if you prefer, and a water repellent finish or two coats of a penetrating sealer.
This requires the same installation steps as the wooden threshold. The exception would be the use of a hacksaw with a fine toothed blade to cut it to length and a metal file to smooth out the roughness. Pre-drill the screw holes to avoid splitting the sill and to ease screw installation.
Vinyl Gasket Threshold
Also called a Thermal Threshold, this wide aluminum strip has a concave plastic strip running down the center. When the door is closed, the vinyl gasket presses against the bottom of the door.