Quick answer
A composite door that won't lock is nearly always a dropped door misaligning the hooks with the keeps, or a worn multi-point gearbox. Lifting the handle mid-air (door open) tells you which: smooth action means alignment, resistance or a dead feel means the gearbox. Most Cornwall call-outs are same-day fixes from £75.
Overview
A composite door that suddenly refuses to lock is one of the most common problems we're called out to in Cornwall. In 9 cases out of 10 it's either a keep alignment issue (the door has dropped and the hooks miss the frame plates) or a failed multi-point gearbox. Both are fixable, often the same day.
Symptoms
- Handle won't lift, or lifts partway and jams.
- Handle lifts but the key won't turn afterwards.
- Loud grinding or clunking as the hooks try to engage.
- You can lock it when open but not when the door is closed against the frame.
Common causes
- The door has dropped on its hinges and the hooks miss the keeps.
- Multi-point gearbox has failed internally.
- Keeps on the frame have worked loose or shifted.
- Debris or a bent hook fouling the mechanism.
- Weather seal has swollen and is holding the door off the frame.
Why this happens more on the coast than inland
We see a disproportionate number of these call-outs in exposed spots like Hayle, Portreath and along the Lizard, where wind-driven rain forces water into hinge recesses and swells timber sub-frames behind the composite skin. That swelling shifts the whole door leaf by a few millimetres, which is all it takes for a hook to catch the edge of its keep instead of dropping cleanly through it.
Inland properties, particularly older granite cottages with slightly out-of-square openings, tend to see the opposite problem: the frame itself has never been perfectly true, so the door has always relied on a fine-tuned hinge setting that slowly creeps out over a few years of use.
Reading the fault before you call anyone
Stand the door fully open and lift the handle without the door touching the frame. If the hooks, bolts and rollers all extend smoothly with a firm spring resistance at the top of the lift, the gearbox itself is healthy and the fault lives in the alignment between the leaf and the frame keeps.
If the handle feels loose, spongy, or only partially lifts before stopping dead, you are looking at a gearbox that has failed internally — a broken cam, a snapped pawl spring or a sheared drive bar. This is not something to force through; forcing a failing gearbox usually finishes the job of destroying it entirely.
- Smooth lift when open, jams when closed = alignment fault
- Stiff or partial lift even when open = gearbox fault
- Grinding or clicking noise = worn hook or cam
- Works some days, not others = seasonal movement layered on a marginal alignment
What a proper alignment repair actually involves
A competent installer doesn't just spray lubricant and hope. The job starts with checking hinge screws are seated into sound timber or PVC reinforcement, then measuring the door's reveal gap at four points to find exactly where it has dropped or twisted.
Hinges on composite doors are usually adjustable in two or three planes (height, compression and lateral), so a millimetre-precision adjustment can bring the hooks back into true alignment with the keeps without needing to touch the frame at all. On a 1930s semi in Falmouth we recently attended, a top hinge had simply worked loose over eight years, dropping the whole leaf by 4mm — a 40-minute fix.
When it's the gearbox, not the door
Multi-point gearboxes are sealed units, typically rated for many thousands of cycles, but grease dries out, springs fatigue, and the plastic cam followers used in some budget mechanisms wear down faster than the steel components around them. On coastal properties we regularly find corrosion inside gearboxes that have taken in salt-laden condensation over several winters.
Replacement means matching the exact backset, case length and hook spacing of the existing mechanism — get any of these wrong and the new unit either won't fit the door edge or won't line up with the existing keeps in the frame, so this is not a part to guess at from a hardware shop shelf.
Security implications of leaving it
A door that 'won't lock' is sometimes read by homeowners as an inconvenience rather than a security gap, but a multi-point mechanism that isn't fully engaging often means the door is only held by a sprung latch — trivially defeated. Insurers can and do decline claims where a known-faulty lock was left unrepaired.
If you run a holiday let, this is a compliance issue too: guests expect a door that locks properly first time, and a jammed lock at changeover on a Saturday afternoon with a new arrival waiting is a genuinely bad first impression.
What we do differently on a call-out
Our vans carry the common gearbox brands used across Cornwall new-builds and retrofits — Yale, Winkhaus, ERA, Fuhr and Avocet — so the majority of these jobs are resolved in a single visit rather than needing a return trip for parts.
We always check hinges and drainage before condemning a gearbox, because a surprising number of 'failed lock' call-outs turn out to be a £75-£120 alignment job rather than a £180-£320 mechanism swap. Being told the cheaper diagnosis first is, frankly, rare in this trade, but it's how we keep repeat customers across the county.
What actually happens when we attend a call-out
We start every visit the same way, regardless of what the customer told us on the phone: door open, handle lifted in free air, watching how the hooks and bolts travel. That thirty-second check tells us more than a five-minute description ever can, because homeowners understandably describe symptoms rather than mechanisms — 'it won't lock' could mean six different faults.
Only once we've confirmed whether the mechanism itself is healthy do we start checking the frame side: keep positions, packer shims behind the hinges, and whether the frame has racked out of square. On a lot of Cornwall properties, particularly ex-council semis with original 1980s frames, the frame has moved more than the door has.
How this fault progresses if you leave it
A door that won't fully lock rarely stays at 'won't lock' for long. The next stage is usually that the handle starts to feel gritty or resistant as the hooks repeatedly catch the edge of a keep instead of dropping through it, chewing small burrs into the metal each time.
Left further, those burrs turn into proper damage on both the hook and the keep, at which point a simple realignment is no longer enough — the worn components themselves need replacing, turning a £75-£120 job into a £180-£320 one. We've seen this play out over a single winter in exposed spots like Portreath.
Brand and mechanism differences worth knowing
Not all multi-point systems fail the same way. Winkhaus mechanisms tend to give a distinct clicking warning as the cam wears before full failure, whereas some older ERA and budget Chinese-import mechanisms fail more abruptly, going from 'a bit stiff' to 'completely dead' within days.
If your door was fitted as part of a new-build development anywhere in Cornwall over the last fifteen years, there's a reasonable chance it uses one of a handful of common gearbox footprints, which is exactly why we keep multiple brands stocked in the van rather than ordering in after diagnosis.
Holiday lets and unoccupied properties
For a holiday let, a lock that won't engage fully between changeovers is a liability most owners don't spot until a guest reports it. We'd recommend a quick lift-and-turn test as part of every changeover clean, because a door that worked fine for the outgoing guests can develop a fault over a few unoccupied days, particularly after a spell of driven rain.
Unoccupied second homes — common along the north coast — have a similar issue: nobody notices the lock has become intermittent until moving day, by which point moving furniture in and out through a door that won't reliably secure is a real headache.
What to tell us on the phone to speed things up
The most useful thing you can tell us is exactly what the handle does when the door is open versus closed, and whether the fault is constant or comes and goes with the weather. Mention if you've noticed the door dragging on the floor or rubbing the frame anywhere, as that points straight to a dropped hinge rather than a lock fault.
If you know the door's approximate age or who installed it, that helps us bring the right gearbox on the first visit rather than a general-purpose one that might not match the hook spacing.
Typical repair costs in Cornwall
| Work | Typical price | Notes |
|---|---|---|
| Hinge and keep realignment | £75-£120 | Most common fix; usually resolved same visit |
| Multi-point gearbox replacement | £180-£320 | Depends on brand and number of locking points |
| Emergency call-out (evenings/weekends) | +£40-£60 | Waived if booked as a standard weekday visit |
| Full mechanism + cylinder combined | £230-£380 | Sensible if both are near end of life |
Guide prices only — we confirm the cost after seeing the door.
When to call a professional
- The multi-point mechanism no longer engages when you lift the handle.
- You can see or feel a broken hook, roller or cam inside the door edge.
- The key turns but the door stays locked, or you are locked out.
- Recent forced-entry attempt or visible damage to the cylinder.
Prevention
- Lubricate the cylinder twice a year with a graphite or PTFE lock spray - never WD-40 or oil.
- Grease the hooks and rollers on the door edge every 6 months.
- Always lift the handle to engage the multi-point locks before turning the key - this takes load off the gearbox.
- Never force a stiff key - book a service call before the mechanism snaps.
