Pile Weatherstrip for Casement Windows
Where casement sashes use pile seals in a groove, weather stripping is a compression problem before it is a material problem. A casement sash swings shut and lands against the frame; whatever sits in the groove has to bridge the gap, hold contact around the whole perimeter, and still let the handle pull the sash in without fighting it. XINHAI — Jiaxing Xinhai Doors And Windows Accessaries Co., Ltd., Jiaxing, Zhejiang — manufactures pile weatherstrip from PP polypropylene yarn, with base widths from 4 mm to 25 mm, pile heights from 5 mm to 20 mm, and a base thickness of 0.8 ± 0.15 mm. This page is about matching that product to a measured groove where casement sashes use pile seals.
Sealing points: where casement window weather stripping has to work
A casement sash has four seal runs: hinge jamb, head, sill, lock jamb. They do not behave the same way.
At the lock jamb, the sash moves inward and presses against the frame. The closing direction is largely perpendicular to the seal line — this is compression contact. The pile bends over and holds the gap closed.
At the hinge jamb, the sash rotates. The seal line sees a lateral wipe as the sash swings, and the pile is dragged rather than pressed. The same happens near corners, where a cam or wedge action can slide the pile a few millimetres before it settles.
That difference affects how the pile survives. Pile bent over in compression springs back. Pile dragged sideways can roll, twist and mat.
Most casement profiles have one groove around the perimeter, so one spec usually serves all four sides. Where the sill sees standing water and the head does not, running different specs per run is reasonable — but most fabricators do not. If you do split the spec, silicone treatment on the sill run is the usual place to spend it.
Why lower pile height usually fits casement compression
Pile is not a solid gasket and does not need to be flattened to zero. It works as a flexible barrier — anti-wind, anti-noise, anti-dust. It blocks the path; it does not clamp the joint shut.
A casement sash closes into a small gap, and the hardware pulls it into that gap every time. If the pile is too tall for the gap:
- Closing force rises. The handle compresses yarn that has nowhere to go.
- The pile takes a permanent set. Yarn crushed flat daily stops springing back and the seal line goes slack.
- The sash can be held off the frame. If the pile bottoms out, the sash never reaches the point where the latch engages properly.
So for casement compression, pile height is normally chosen at the lower end of our 5–20 mm range — sized to the measured closed gap plus a small amount of interference. Enough to bend and stay in contact, not enough to be crushed flat. Match pile height to the measured gap, confirmed by test on one window.
Base width and thickness are separate constraints and are not negotiable. The base has to sit in the groove without binding, at 0.8 ± 0.15 mm thickness. Base widths run 4–25 mm, and pile-width codes such as 6.9 (4P) and 4.8 (4P) are quoted separately.
Silicone treatment for casement window weather stripping
We offer pile with silicone treatment or without. The decision is mostly about where the seal sits, not about one option being better in an absolute sense.
Exterior-exposed runs — sill, hinge jamb, anywhere rain and UV reach the yarn — are the usual candidates for silicone treatment. Supplier-stated silicone treatment includes multi-channel silicone oil treatment, better waterproof effect, anti-aging ingredients, elastic pile, and more than 50,000 frictions without deformation. Elastic pile matters more on a casement than on a slider, because the hinge-side wipe drags across the pile.
Interior, dry or sheltered runs are the usual candidates for non-silicone.
Adhesive backing is a separate option and a separate decision. If the strip sits in a groove, you generally do not need adhesive. If you are applying to a flat surface, adhesive backing helps hold position during assembly. A plastic fin is a third option: it places a plastic fin in the middle of the pile, and the fin can sit at the same height, higher, or lower than the pile, in plastic or fabric. A fin adds a stronger wind and water barrier and also adds closing resistance — check it does not hold the sash off the frame before committing a full run.
Colour and yarn density
Two things buyers ask about that we will not invent numbers for.
Colour. We do not publish a colour chart here. Tell us the colour you need — matched to the profile, or neutral — and we will confirm what we can run on your spec.
Density. Yarn density is set against the gap and the closing force, not picked from a catalogue page. A denser pile blocks more and resists dust passage better; it also pushes back harder. On a casement, where the hardware is already pulling the sash in, that pushback is the trade-off. Density options are available; confirm density on the RFQ.
Measuring the sash groove before you order
Measure the groove, not the old pile. Old pile is matted and reads short.
Three measurements, taken at several points along each run:
- Groove width — sets base width. Extrusion tolerances and corner weld buildup mean the groove is not the same at the corner as mid-span.
- Groove depth — sets how much base plus pile can sit inside the profile. Base thickness is 0.8 ± 0.15 mm; a groove machined at nominal minus tolerance can pinch it.
- Closed gap — measure with the sash shut and latched, at lock jamb, hinge jamb, head and sill. This sets pile height.
Length is customized, so order by run and add corner allowance. Do not assume the four runs are equal.
Retrofit replacement notes
Retrofit is measurement work, not a parts-bin job.
Pull the old strip and clean the groove. Adhesive residue left in the groove will hold the new base off the floor and cost you pile height.
Match base width and base thickness first. If the new base does not seat, nothing else matters. Then set pile height from the measured closed gap, not from the old strip.
Check the groove for damage. A groove that has been scraped or widened will not retain a base that fits everywhere else.
Test one window before running the batch: closing force by hand, latch engagement, and water path at the sill. Then commit.
On quantity: our Alibaba listings show a MOQ of 20,000 meters. For a single-building retrofit that is a lot of strip — if that is your situation, say so when you send the spec and we will tell you what is possible rather than waste your time.
Factory figures are supplier-stated: 20+ production lines, 2,000 m², daily capacity 300,000 meters. ISO 9001 was announced in our company news in April 2019; we do not claim current certification here.
Next step: send your base width, pile height and options — silicone or non-silicone, adhesive or none, fin or plain pile — plus total length and the closed gap you measured, to [email protected] or +86-573-86779825. If you would rather narrow the spec first, start with the Pile Weatherstrip Selector, or compare base configurations in pile weatherstrip profiles.