Signs Your uPVC Window Mechanism Needs Replacing (and How to Replace an Espag)

The short answer

The signs of a worn uPVC window mechanism are a handle that turns but doesn't lock, cams that don't move, grinding or crunching as you turn the handle, and a window that won't stay open or close tight.

Do this test first: open the window and turn the handle. If the cams on the edge move smoothly with the window open, but the handle is stiff when it's shut, the mechanism is fine. The keeps or alignment need adjusting instead.

A worn espag is a screwdriver job to replace. Match the length, inline or offset, and the backset.

A window that's stiff, won't lock or won't stay open usually needs one part replacing, not a whole new window. Here's how to tell which part has failed, and how to replace a worn locking mechanism (the espag) yourself.

Replacement espags

Best seller

Inline Espag£8.99

Gearbox in the middle of the strip
250, 400, 600 or 800mm
20mm or 22mm backset

Choose this if: the gearbox on your old espag is in the middle of the strip.

View inline espags

Offset

Offset Espag 5.0 (2 reviews) £8.99

Gearbox set to one side
250, 400, 600 or 800mm
20mm or 25mm backset

Choose this if: the gearbox on your old espag is set to one side.

View offset espags

Keeps

Universal Espag Keeps 5.0 (1 reviews) £9.99

Pair of keeps
3, 4 and 5mm clip-on packers
Fits most profiles

Choose this if: the handle is stiff only when the window is shut, or doesn't pull in tight.

View the keeps

Just the handle

Home Secure Universal Handle 4.8 (44 reviews) £4.99

Five spindle lengths included
Left or right-hand espag windows
No measuring needed

Choose this if: the spindle has snapped, or the handle is cracked or loose.

View the handle

Not sure which espag you've got?

Send a photo of your espag with a tape measure along it to info@homesecureshop.co.uk and we'll match it.

Call 0151 521 8089

4.8 from 1,000+ reviews
Same-day dispatch, order by 2pm
Trade counter in Aintree, Liverpool
Window experts on the phone

Inline or offset?

Feature	Inline Espag	Offset Espag
Our verdict	Best seller	Offset
Gearbox position	Middle of the strip	To one side
Customer rating	New	★ 5.0 (2)
Backset	20mm or 22mm	20mm or 25mm
Lengths	250 to 800mm	250 to 800mm
Price	£8.99	£8.99
Shop	View	View

Swipe the table sideways to compare.

Our counter tip

Take the old espag out before you order. You can measure the length, see where the gearbox sits and check the backset in seconds, and it's the surest way to get the right one first time.

The Home Secure counter team, Aintree

Warning signs, and what they mean

Sign	Usual cause
The handle turns freely, but the window doesn't lock	The espag gearbox has failed, or the handle's spindle has snapped
Grinding, clicking or crunching as you turn the handle, even with the window open	A worn espag
The handle is stiff only when the window is shut	Keeps or alignment. The window has dropped, or the keeps are out of line.
Draughts or rattling with the window locked	Worn keeps, worn friction stays, or tired seals
The window won't stay open, or drops when opened	Worn friction stays (the hinges)
The handle is cracked, wobbly or won't lock with its key	The handle

For friction stays, see our guide to window mechanisms, which shows you how to measure them.

The 30-second test: mechanism, keeps or handle?

Open the window and turn the handle through its positions. Watch the cams (the small rollers or mushrooms) along the edge of the window.
If they move smoothly with the window open, the espag is fine. If the handle is only stiff when the window is shut, the cams are fighting the keeps. Adjust the keeps or the window's alignment.
If the handle turns but the cams don't move, take the handle off (two screws under the cover at its base). If the square spindle has snapped, you only need a new handle. If it's whole, the espag gearbox has failed.
If it grinds or sticks with the window open, the espag is worn. Replace it.

Don't force it. Leaning on a stiff handle is how a worn espag or keep becomes a snapped spindle or a window that won't open at all.

Is it just the handle?

White lockable uPVC espag window handle fitted to a window

Handles wear too, and they're the cheapest part to replace. Replace the handle if it:

wobbles even after you've tightened the screws
is cracked or faded
won't lock with its key
has a snapped or worn spindle

A new handle won't fix a worn espag, so do the test above first. Our Home Secure universal handle comes with five spindle lengths, so you don't need to measure.

Spindle snapped?

You only need a new handle. Ours comes with five spindle lengths, so there's nothing to measure. £4.99.

View the handle

How to replace a uPVC window espag

Inline espag window locking mechanism for uPVC windows

Open the window and turn the handle to the open position.
Take the handle off. Lift or twist the cover at its base and undo the two screws.
Undo the espag. Undo the screws along the metal strip on the opening edge of the window, and slide the espag out.
Measure the old one:
- Length, end to end: 250, 400, 600 or 800mm.
- Inline (gearbox in the middle of the strip) or offset (gearbox to one side).
- Backset, from the face of the strip to the centre of the spindle hole: 20mm or 22mm for inline, 20mm or 25mm for offset.
Fit the new espag the same way round, in the same position, and screw it in. Don't overtighten.
Refit the handle and turn it through its positions with the window open. The cams should move smoothly.
Close and lock the window. If it's stiff, or doesn't pull in tight, adjust or replace the keeps on the frame.

Keeps worn? Our universal espag keeps come with 3mm, 4mm and 5mm clip-on packers to suit your frame. Screws won't grip? See our screws guide.

Measured your old espag?

Inline and offset espags in 250, 400, 600 and 800mm. Same-day dispatch if you order by 2pm.

Shop window espags

Tilt and turn windows

Tilt and turn windows use a brand-specific gear system that's more involved to replace. Send us a photo of the mechanism and any brand name on it, and we'll tell you what we can supply.

Need help?

Send a photo of your espag, with a tape measure along it, to info@homesecureshop.co.uk, or call us on 0151 521 8089. You can also bring the old one to our Aintree trade counter, and we'll match it.

View all window mechanisms

Helpful guides

uPVC Window Mechanisms: Friction Stays vs Espags (and How to Measure Each)

How to Replace a uPVC Window Handle (5-Minute DIY Guide)

Are uPVC Window Handles a Standard Size? What We Actually Sell

Screws for uPVC Windows & Doors: Self-Tapping, Repair or Jack Nut?

FAQ

The handle turns but the window doesn't lock, the cams don't move, the handle grinds or crunches even with the window open, or the window won't stay open or close tight. Open the window and turn the handle to see which part is at fault.

If it's only stiff with the window shut, the cams are fighting the keeps: the window has dropped or the keeps are out of line, so adjust them. If it's stiff or grinds with the window open, the espag mechanism inside is worn and needs replacing.

Take the handle off and look at the square spindle. If it's snapped, you only need a new handle. If it's whole but the cams don't move when you turn it, the espag gearbox has failed and the espag needs replacing.

Not usually. If the gearbox is worn or broken, replace the whole espag. It's a screwdriver job: take the handle off, undo the screws along the strip and slide it out. Match the length, inline or offset, and the backset.

Don't force the handle, as that can snap the spindle or damage the mechanism. Check whether the handle turns fully or feels loose. If it turns but nothing moves, the espag gearbox has failed. Call us with a photo and we'll talk you through it.