Direct answer: To replace an exterior door threshold seal, first make sure the draft or leak is really coming from the bottom threshold, then remove the old gasket, clean the track, install the same profile, and test the closed door for even contact.
A good threshold repair is about fit, not force. If the door is square and the threshold is solid, this is usually a clean homeowner job. If the frame is rotted, the threshold is loose, or the door has to be slammed, fix that bigger problem before blaming the seal.
Before you start: Match the old seal profile and threshold track style. A seal that is close but not the same can make the door hard to latch or still leave gaps.
The bottom of an exterior door has a few parts that all get blamed for the same draft or leak. Use this quick check so you fix the part that is actually failing.
This page fits when: The gasket in the threshold track is worn, torn, loose, or no longer touching the bottom of the closed door.
Check something else when: If the threshold seal looks healthy, check the door sweep and side weatherstripping before replacing this gasket.
This page fits when: This page helps only if the threshold gasket is also worn. A torn sweep on the bottom of the door is a separate part.
Check something else when: If only the sweep is damaged, you likely need to replace or adjust the door sweep instead. This page is for the gasket in the threshold track.
This page fits when: A threshold seal can help when the gap is even and the seal profile is clearly worn.
Check something else when: If only one corner leaks, inspect corner pads, hinge sag, latch alignment, and side weatherstripping. A new threshold seal may not close an alignment problem.
This page fits when: Do not treat this as a gasket job until the structure is solid.
Check something else when: Soft wood, swelling, rot, or water under the threshold means the sill or subfloor needs attention before any seal will last.
Use the profile and track fit as your reference: the replacement seal should match the old gasket and sit evenly in the aluminum threshold channel.
If it works: You found visible wear or a poor seal at the threshold gasket, and the threshold itself is still solid enough to reuse.
If it doesn’t: If the seal looks intact, check the door sweep, side weatherstripping, and threshold adjustment before ordering a replacement seal.
If it works: The old seal is fully removed and you can see the full channel or mounting area.
If it doesn’t: If the seal will not budge, work from both ends and loosen it a little at a time. Damaging the threshold creates a bigger repair than the seal you came to fix.
If it works: The threshold is clean, dry, and ready for the new seal.
If it doesn’t: If residue keeps the channel rough or sticky, clean it again until the new seal can slide or press in without binding.
If it works: The new seal matches the old style closely and is cut to the correct length.
If it doesn’t: If the new seal profile is clearly different or much taller or wider than the old one, pause and get a better match before installing it.
If it works: The new seal is fully seated, even across the threshold, and the door closes against it with light resistance.
If it doesn’t: If one section pops up or shifts, reopen the door and reseat that section before testing again.
If it works: The door closes normally, the bottom edge seals evenly, and no draft or water gets past the threshold in normal use.
If it doesn’t: If you still have a leak or draft, inspect the door sweep, threshold height, corner gaps, and side weatherstripping for a second source.
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If the gasket mounted in or on the threshold is cracked, flattened, or missing, replace that first. If the threshold seal looks good but the flexible strip on the bottom of the door is torn or not reaching the threshold, the door sweep may be the real issue.
Yes, if the threshold is still solid, straight, and able to hold the new gasket. If the threshold is loose, rotted, badly corroded, or damaged where the seal mounts, replacing only the seal usually will not last.
That usually means the profile is too tall, too wide, reversed, or not fully seated in the channel. Double-check the fit and orientation first. If it is installed correctly and the door still will not close normally, you likely need a better-matched replacement or a threshold adjustment.
Usually no, if the seal is designed to press into or slide into a threshold channel. Use the mounting style the threshold was designed for. A mismatched seal should not be glued in as a workaround.
The leak may be coming from a worn door sweep, side weatherstripping, an out-of-adjustment threshold, a bad corner pad, or water getting under or around the threshold assembly itself. If the floor or framing is staying wet, inspect for hidden damage and a larger sealing problem.