Exterior door thresholds are hardworking utilitarian fixtures that are under almost constant stress due to frequent foot traffic, moisture, temperature variations, friction and vibration. When thresholds are sound, they are hardly noticeable. Once they show signs of wear such as splitting, cracking or warping, they can no longer keep out wind and insects, or help to maintain the energy efficiency of your residence. Depending upon the size of your doorway, the extent of the damage, and whether your existing threshold is wood or metal, this project can be finished in 1 to 3 hours. Replacing your exterior door threshold is a straightforward and simple project that a beginning to intermediate do-it-yourself homeowner can execute without too much difficulty. In addition to the list of materials needed, all that is required is mild weather and a clear day.
Open the door and secure with a doorstop or heavy object such as a brick. Put on the knee pads and safety goggles. Wear protective gloves if the old threshold is broken or splintered.
Pry away the damaged wooden door threshold carefully with a crowbar to avoid damaging the door's frame.
Measure your replacement threshold, and the base of the doorway. Cut the new threshold to size using the saw.
Lay the new threshold in the doorway to make sure that it fits well. Wooden shims may be needed to support uneven surfaces. If necessary, notch the ends of the new threshold so that it snugly fits without any gaps in the doorway. Use your sandpaper or an electric sander (see the image above) to sand the cut edges smooth. Apply caulk to the bottom and at either end of the new threshold and press it into place.
Make sure to pre-drill holes in the threshold for the finishing nails. Securely nail the threshold to the sill. Countersink the nail heads and fill in the holes with putty. Sand the threshold again and coat it with a moisture resistant clear sealant or polyurethane.
If your original threshold is metal, you can unscrew it for removal. To cut an aluminium (or other type of metal) threshold, you will need a hacksaw or sabre saw with a metal-cutting blade. As always, put on your safety goggles before cutting.
Do not omit the knee pads. You may be kneeling for an extended period during this project. Be kind to yourself and put them on over your clothing before you begin.