How to Replace a Window Weatherstripping

Step 1: Make sure weatherstripping is really the problem

1. Open and close the window slowly and look for visible gaps where the sash should seal against the frame.
2. Check the existing weatherstripping for cracks, flat spots, missing sections, loose adhesive, or pieces that pull free by hand.
3. Feel for drafts on a cool or windy day, or look for light showing through around the sash where it should be sealed.
4. Compare both sides of the window if only one side seems to leak, since uneven wear can make the bad section easier to spot.

If it works: You found worn, loose, flattened, or missing weatherstripping that lines up with the draft or leak area.

If it doesn’t: If the seal looks intact, check for a warped sash, damaged frame, failed caulk, or drainage problems before replacing parts.

Step 2: Open the window and remove the old strip

1. Set the window in a stable open position so you can reach the weatherstripping comfortably.
2. Start at one end and gently pull the old strip free. If it is stuck, use a putty knife or small flat screwdriver to lift it a little at a time.
3. Remove any clips, staples, or leftover adhesive carefully so you do not gouge the frame or sash.
4. Keep a sample of the old weatherstripping if possible so you can match the profile and thickness.

Step 3: Clean and inspect the mounting surface

1. Wipe the channel, groove, or contact surface with a rag and mild cleaner to remove dust, old adhesive, and grime.
2. Dry the area fully so the new weatherstripping can sit flat and, if adhesive-backed, stick properly.
3. Check for bent metal, packed debris, paint buildup, or rough spots that would keep the new strip from seating evenly.
4. Lightly scrape away stubborn residue so the replacement can lie flat from end to end.

Step 4: Cut the new weatherstripping to fit

1. Measure the length of the section you removed, or measure the full sealing area directly on the window.
2. Compare the new weatherstripping profile to the old one so the shape, width, and compression look close.
3. Cut the replacement to length with a utility knife or scissors, making clean square ends unless the original used angled corners.
4. Dry-fit the piece before final installation to make sure it reaches the full sealing area without bunching up.

Step 5: Install the new weatherstripping

1. Start at one end and press the new weatherstripping into the channel or onto the contact surface, following the same path as the original.
2. Work along the full length a little at a time so the strip stays straight and does not twist.
3. Press firmly along the entire piece so it seats fully, especially at the ends and corners.
4. If the window uses multiple sections, install each one so the seal is continuous and the ends meet neatly without large gaps.

If it doesn’t: If a section lifts or shifts, remove that section and reinstall it before testing the window.

Step 6: Close the window and test the seal in real use

1. Open and close the window several times to make sure it moves smoothly and latches normally.
2. Check that the sash compresses the new weatherstripping enough to seal, but not so much that the window binds hard.
3. On a windy day, feel around the repaired area for drafts, or lightly spray the exterior and check inside for water entry if that was the original problem.
4. Look again after a day or two of normal use to make sure the strip has stayed in place and the ends have not pulled loose.

If it works: The window closes normally, the seal feels tighter, and the draft or minor leak at that location is gone.

If it doesn’t: If the window still leaks or drafts, recheck the weatherstripping profile and look for other causes like frame movement, sash misalignment, or exterior water intrusion.