Clean the frame with alcohol and let it dry, measure the gap with the window closed, pick a strip a little taller than the gap, then peel the backing a few centimetres at a time and press the strip onto the frame stop – not onto the moving sash edge. Butt the ends at corners instead of stretching the strip, and close the window for 24 hours so the adhesive sets.
IllustrativeWhat you need
- Self-adhesive foam strip (EPDM foam for long life)
- Isopropyl alcohol and a cloth
- Scissors or a sharp knife, tape measure
- A dry day above about +10 °C – adhesive bonds poorly on cold frames
Step by step
- Remove the old strip and scrape off old adhesive.
- Clean the frame with alcohol; let it dry completely.
- Measure each side of the frame stop.
- Peel 5–10 cm of backing, press the strip into the corner and work along – don't pull it tight, stretched foam shrinks back and opens a gap.
- Cut at each corner and start a new piece; butt the ends together.
- Close the window and check it still latches.
Where to place it
| Window type | Strip position |
|---|---|
| Casement / tilt-turn | On the frame rebate (stop) where the sash closes against it |
| Sliding window | Wool pile in the sash track; foam only on the fixed meeting rail |
| Sash (hung) window | Pile or V-strip at the meeting rails and sides |
If the window won't close
The strip is too tall. Swap to a lower profile (D → P → E → I) instead of forcing the latch – an over-compressed strip loses its spring quickly.
Quick questions
Can I put new weatherstrip over the old one?
No. Remove the old strip and adhesive; new tape does not hold on old foam.
Which side of the window does the strip go on?
On the fixed frame stop, so the sash presses onto it when it closes.
Need a seal for this?
Send your section, gap size or a photo of the old seal – Dora replies usually within 2 hours. Door & window seals are available from 10 m.