Things You'll Need
Putty knife or scraper
The door threshold plays a critical role in keeping your home airtight. A properly installed threshold helps to keep pests out, but it also reduces cold drafts and helps maximize energy efficiency. Over time, thresholds can suffer wear and tear thanks to foot traffic and exposure to rain and snow. If your threshold is showing its age, take the time to replace it to ensure that your entry door continues to function as intended.
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Open the door to expose the threshold. Use a heavy item to prop the door open while you work, and remove the screws holding the old threshold in place.
Put on your safety glasses and cut the threshold in half using a reciprocating saw. If your threshold is made of metal, equip the saw with a metal cutting blade first.
Pry the threshold out using a hammer and pry bar. If your threshold is made of metal, use a drill to remove screws attaching the threshold to the door sill before attempting to pry it out of the opening.
Use the old threshold as a pattern, and cut the new one to size using a hacksaw. Use a saber saw with a metal cutting blade to cut a metal threshold to size.
Scrape away any old caulk from the door sill to level the surface. Sweep and remove debris from the sill before proceeding.
Inspect the sill carefully for any signs of deterioration. If you see signs of rot or insect damage, you should make repairs to the sill before proceeding.
Press the threshold into place to see if it fits. Slide the ends under the door stops on either side, or under the jambs if they are undercut to receive the threshold. While the threshold is in place, pre-drill any fastener holes in the sill. Remove and trim the threshold further if needed for proper fit.
Tap the threshold in place gently with a hammer positioned along the side of the threshold. Tap each end into place a bit at a time to ensure the unit is positioned evenly from front to back.
Slip wooden shims between the sill and threshold at the center and either end of the threshold. Tap each gently with a hammer to make the sill snug and level in relation to the bottom of the door. It should be tight against the door stops and casing. Once the threshold is correctly positioned, break off any part of the shims that stick out past the sill.
Squirt expanding polyurethane sealant into the gaps beneath the threshold to seal off drafts and help to hold it in place. Apply a bead of sealant where the threshold meets the door jamb on either side, and screw the threshold down. Screws should be countersunk so they won't snag on passing feet. Allow the sealant to dry before stepping on the threshold.
If your door stops -- the parts of the door frame that jut out where the door meets the frame -- are not undercut to receive the threshold, use a saw to undercut them the thickness of the new threshold. This allows you to slip the threshold underneath the stops for a snug installation.
It's a good idea to treat the sill and other underlying wood with a borate product to prevent future insect and fungal damage.
A layer of flashing over the sill will help protect it from stress and weathering.
Wear safety glasses to protect your eyes when cutting wood or metal.