How do I replace a uPVC window friction stay?

The friction stay is the pair of steel arms that carry a uPVC casement out and hold it against the wind. It is the hardest-worked part of the window and the one that fails first.

Safety

What you'll need

• A replacement stay of the correct length and track width
• A Pozidriv screwdriver or driver bit
• A helper, or a prop for the sash
• PTFE lubricant

Step by step

1. Confirm the stay is the fault.A window that drops at the outer corner when open, will not stay open in a breeze, or that has become stiff and grinding, is usually a stay. A window that closes but does not lock is usually the gearbox.
2. Open the window fully and look.A bent arm, a shoe that has come out of the track, or a sheared rivet is visible immediately. So is a missing friction pad in the shoe.
3. Try the friction screw before replacing anything.Many stays have a small screw in the sliding shoe that tensions the nylon friction pad. If the window opens but will not stay put, this screw is the first thing to try.
4. Measure the stay along the track.End to end of the metal track, in millimetres. Common sizes run from 200mm to 600mm. Measuring the window opening instead gives the wrong answer.
5. Measure the track width.13mm and 17mm are the two standards and they are not interchangeable. Measure the channel the stay sits in, not the arm.
6. Decide standard, egress or restricted.A standard stay opens to about 90 degrees. An egress stay swings the sash clear for escape. A restricted stay stops at around 100mm. Replace like for like unless you are deliberately changing it.
7. Support the sash before undoing anything.Prop it, or have someone hold it. Once both stays are off, the sash is loose in your hands and it is heavy.
8. Undo the sash screws first.Then the frame screws. Working in that order keeps the sash hanging on the frame arms until last.
9. Replace both stays on a window.They wear together. A new stay paired with a worn one carries all the load and fails quickly, and the sash sits out of square.
10. Fit the new stays with the sash closed if you can.Offer the stay into the frame channel, start the screws, then align the sash and fix the sash arm. It is far easier than trying to hold a sash open at the right angle.
11. Check the operation before fully tightening.Open and close a few times with the screws just snug, then tighten. A stay screwed down misaligned binds immediately.
12. Lubricate the track.PTFE on the track and the shoe. Not oil, which collects grit and accelerates the wear you have just repaired.

Tips

• Take the old stay with you or photograph it against a tape measure. Suppliers match them by length, track width and hole pattern.
• If the sash has dropped so the handle no longer lines up, worn stays are usually the cause rather than the hinges — uPVC casements have no separate hinges.
• Stainless stays cost a little more and are worth it on a coastal or exposed elevation where plated steel corrodes within a few years.

Common mistakes

• Measuring the window rather than the stay — The stay is shorter than the opening and its length is a standard size in its own right. Ordering by the window dimension gives a stay that either will not fit the channel or does not open the sash properly.
• Replacing one stay and leaving the other — The two arms share the sash's weight. A new one alongside a worn one takes almost all the load, twists the sash out of square, and fails within a year or two.

If it doesn't work

Questions people ask