Why Has My uPVC Window Dropped and Started Catching the Frame?
For a side-hung or top-hung uPVC casement sash that has become slightly lower or skewed and now scrapes, catches or needs lifting to close.
What this usually means
A uPVC window sash can start catching because the friction stays have worn, the sash has dropped, fixings have loosened or the window has lost its original guidance. ERA specifically notes that hinge hardware and hinge bolts are designed to reduce sash drop and keep the sash returning to its prescribed position. If the window needs lifting or force to close, repair the alignment or hardware before the lock and frame are damaged.
What may be causing this
Friction stays have worn
Clues: The sash visibly settles as it opens and catches near the opposite corner.
What to do: Replace correctly sized stays.
The sash has lost alignment within the frame
Clues: Gaps around the perimeter are no longer even.
What to do: Have sash position and hardware adjusted.
Hinge or frame fixings have loosened
Clues: There is visible movement at hinge mounting points.
What to do: Stop using the sash heavily and arrange repair.
The sash is unusually heavy for the existing stays
Clues: The problem recurs after adjustment or affects a large glazed sash.
What to do: Use hardware with the correct load rating.
How to check what is happening
The sash is misaligned.
Worn stays are likely.
Sagging/alignment is more likely than a swollen frame.
Can you fix this yourself?
Avoid planing, filing or forcing a uPVC frame. The correct repair usually involves hardware or alignment, not removing frame material.
- Torch
- Phone camera
- Straight edge for visual comparison
What you can safely try
- 1
Find where it catches
Mark the contact point mentally without forcing the sash.
- 2
Compare frame gaps
Uneven gaps help distinguish sash drop from a local seal problem.
- 3
Inspect hinge movement
Look for looseness or a sash that drops when opened.
- 4
Repair before the lock is damaged
A fitter can correct alignment and replace worn hardware.
Call a window fitter if…
- The sash feels loose or could detach.
- Hinge screws or arms are pulling away.
- The window is an escape window and cannot open reliably.
- Repair would require external access at height.
Get the right window fitter.
We already know this problem maps primarily to a window fitter. Choose the closest type of work, add your postcode and continue in the form.
Sources used for this guide
We prefer primary UK guidance, regulators and manufacturers for technical and safety-sensitive claims.
Last reviewed: 2 September 2026. Home Manual updates review dates only when the substance of a guide is checked or changed.