That sloped lump of wood or metal on the floor at the base of your front door is called the sill. It is also called the saddle or threshold. Years ago sills were only wood, but have been replaced, for the most part, with an aluminum type. Metal, particularly aluminum, is considerably more durable and far less expensive than the hardwoods that once adorned most entries.
If you have an older home with a wood door sill, it probably is beginning to show wear and tear. Winter rain, snow, summer heat and the sun's ultraviolet rays take a toll on exterior wood surfaces of all kinds. Once a sill has deteriorated to the point where there are more splits in the wood than grain lines, painting it is only a temporary fix. It will require a heavy coat of paint twice a year.
It should be noted that the sill is the only barrier between the elements and the floor framing at the door opening. If the sill is deteriorated and leaking, water could reach the adjacent subfloor and framing causing fungus damage and rot an expensive condition to repair.
Our advice is to change the sill when its condition becomes questionable. If the existing sill is made of wood, we recommend wood replacement for two reasons: It is wise to maintain architectural integrity by matching what exists when a repair or alteration is performed, and wood is more elegant. Also, with proper installation and maintenance a wood sill can last several decades.
Remove the old sill by removing a chunk from the middle. Two saw cuts is all it will take. Be careful not to damage adjacent flooring when making these cuts. Next, use a chisel to split the two sides that remain along the grain (parallel to the length), keeping in mind that in many instances the threshold ends that lie below the door frame are nailed or screwed to either the floor or the door frame itself. Splitting will make removal easier when this is the case. More splits will result in smaller pieces to remove and less chance of damage to the surrounding area.
Clean the area thoroughly, remove all protruding screws and nails and make the new threshold ready to fit by measuring and cutting it. When retrofitting a threshold one will rarely be able to "slip" the new piece into place. This is because the thickest side of the tapered piece faces inward and will neither fit below the door jamb from the outside or between the floor and jamb from the inside. The process is not difficult, all you have to do is notch one end of the threshold to match the shape of the door frame. Holding the threshold at an angle to the floor, slip the un-notched end under the door jamb on one side, and then simply lay the notched end down the opposite jamb. Once it is flat on the floor, slide the jamb an eighth of an inch or so toward the notched side to hide the cutting. And, use several strong weather-resistant screws to hold everything in place.
IMPORTANT NOTE: It is essential that a new threshold be laid in a bed of caulking to prevent attack from moisture. Several long beads of caulking running from side to side in the opening should do the trick. Caulking should ooze out of the threshold at all locations as it is screwed tightly in place. If it doesn't, remove the sill and add more caulking.
