Size a pile seal with two numbers: the base width that fits the groove in the frame, and a pile height about 0.5–1 mm greater than the gap it must close. Choose a finned pile for exterior sliding windows and doors, where draught and water resistance matter.
Base width × pile height
Pile seals are described as base width × pile height, for example 4.8 × 6 mm. The base must slide into the groove snugly; the pile must touch the opposite surface lightly so the sash still slides.
| Pile height vs gap | Result |
|---|---|
| Too short | Visible gap, draughts and dust |
| About 0.5–1 mm more than the gap | Light contact, easy sliding – correct |
| Much too tall | Pile bends over, sash is stiff, pile wears fast |
Finned or plain?
A thin plastic fin inside the pile stops air and water far better than pile alone. Use finned pile for exterior sliding windows and doors, plain pile for interior wardrobes and light uses.
Measuring an old seal
Pull out a short piece and measure the backing width with a caliper and the pile height from the backing to the tips. Send us a photo of the piece next to a ruler with your enquiry.
Quick questions
Can I use a self-adhesive brush seal instead?
Yes, on frames without a groove. It is easier to fit but the adhesive must go on a clean, dry surface.
Need a seal for this?
Send your section, gap size or a photo of the old seal – Dora replies usually within 2 hours. Brush & wool pile seals are available from 10 m.