A window that won't lock is a security risk — most causes are mechanical and fixable without replacing the whole unit.
If the handle is stiff or completely jammed, the most common cause is the multi-point locking gearbox inside the sash binding, often because the window has dropped slightly on its hinges and the locking pins no longer line up with the keeps on the frame. Forcing the handle can snap the internal mechanism, turning a simple adjustment into a full gearbox replacement, so it is worth stopping and checking alignment before applying more force.
This usually means the locking pins are engaging but not fully seating into the keeps, which happens when the window sash has dropped or the frame has moved slightly, often due to age, heavy use, or a hinge starting to fail. A locksmith or installer can adjust the keeps or hinges to restore correct alignment in most cases without replacing any glass.
The keeps are the metal receivers on the frame that the locking pins engage into. Over years of use they wear, especially on frequently used windows, and eventually the pins slide past rather than locking home. Keeps are a relatively inexpensive replacement part and swapping them out often restores full function without touching the sash or gearbox.
uPVC window mechanisms are metal components inside a plastic housing, and if they are never lubricated they stiffen and eventually seize, particularly in exposed coastal or north-facing locations. A light silicone-based spray lubricant applied to the hinges, locking points and gearbox track twice a year prevents most mechanical locking faults before they start.
If the handle spins freely without engaging the mechanism, or moves with a loose, disconnected feel, the internal gearbox has likely failed and needs replacing rather than adjusting. This is a same-day job for an experienced fitter on most standard uPVC casements, and it is far cheaper than replacing the whole window.
A window that cannot be fully secured is a genuine vulnerability, particularly on ground floor and easily accessible upper floor windows. Until it is repaired, use any secondary restrictor or additional bolt available, and treat the repair as a priority rather than something to leave for months.
Yes, in the majority of cases. Locking faults are almost always down to worn keeps, misaligned hinges or a failed gearbox, all of which are replaceable parts rather than reasons to replace the whole window.
Simple adjustments and keep replacements are inexpensive, while a full gearbox replacement costs more but is still significantly cheaper than a new window. An installer can usually quote after a quick inspection.
No, particularly on accessible windows. Treat it as a security priority and get it inspected promptly, using any secondary locking device you have in the meantime.
Sashes gradually drop over time due to the weight of the glass on the hinges, which is a normal ageing process. This slowly moves the locking pins out of alignment with the keeps until the lock stops engaging properly.
A window that's become a struggle to open is rarely broken beyond repair — usually it just needs cleaning, adjusting or lubricating.
A window that sags, won't stay open, or feels loose on its hinge is a common and usually inexpensive fix.
A snapped key is usually a sign of a worn lock or cylinder — and a good opportunity to upgrade your door's security.
Black mould on window frames is a moisture problem, not a cleaning problem — here's how to find the real cause.
A snapped door handle is one of the most common uPVC door faults — and one of the quickest to fix correctly.
A door that scrapes the frame or is hard to lock hasn't broken — it has simply dropped, and it can usually be adjusted back.
Call us on 07424 714402 for a quick diagnosis of your window lock, or book a free survey if it's time to consider replacement.
