Quick answer
A stiff composite door lock is usually dried-out lubricant, a slightly dropped door dragging the hooks, or early gearbox wear. It's a warning sign, not a nuisance — leaving it risks a snapped key or a seized mechanism. A service visit costs £75-£150 and prevents the far costlier failure that follows if ignored.
Overview
A lock that feels stiff, gritty or needs two hands to turn is telling you something is wrong. Ignoring it almost always ends in a snapped key or a seized gearbox. The fix is usually a proper clean, lubrication and a hinge adjustment.
Symptoms
- Key needs firm pressure to turn.
- Handle needs a shove upwards to engage the hooks.
- Locking is fine open but stiff when closed.
- Cold mornings are noticeably worse.
Common causes
- Cylinder is dry or contaminated with dust and old oil.
- Door has dropped slightly, so hooks are dragging.
- Gearbox internals wearing - grease has dried out.
- Frame has moved (common on new-build settlement).
Stiffness is a symptom, not the problem
Homeowners often describe a stiff lock as if it were the whole fault, but stiffness is really the door telling you that something upstream has changed — the alignment has shifted, the lubricant has failed, or a component inside the gearbox is starting to bind. Treating the symptom with oil and ignoring the cause simply delays a worse failure.
We've lost count of the call-outs in Cornwall where a customer says 'it's been getting harder to turn for months' and by the time we arrive the key has already started to bend slightly from the repeated extra force being applied.
Cold mornings make everything worse
Composite slabs and the multi-point mechanisms inside them both respond to temperature. On cold Cornish mornings — particularly after a damp night near the coast — old grease thickens and the door leaf itself contracts fractionally, tightening tolerances that were already marginal.
If your lock is noticeably worse first thing and eases off by mid-morning, that's a strong clue you're dealing with a combination of dried lubricant and a door sitting right on the edge of correct alignment, rather than a catastrophic mechanical fault.
The right way to lubricate — and what ruins locks
A dedicated graphite or PTFE-based lock lubricant is the only product that belongs in a Euro cylinder. General-purpose oils and aerosol sprays like WD-40 feel like they help for a day, then attract dust and grit that binds the pin stacks even harder than before.
We see this constantly on service visits: a lock that was 'fixed' with kitchen-cupboard oil eighteen months ago, now gummed with a black paste that has to be flushed out before the correct lubricant can even do its job.
- Graphite or PTFE lock spray only — never oil, WD-40 or grease from a tube
- Apply into the keyway and work the key several times, don't just spray the surface
- Lubricate hooks and rollers on the door edge separately with a light PTFE spray
- Twice-yearly is enough for most homes; more often for exposed coastal doors
How to tell if it's alignment, not just dry lubricant
Test the lock with the door standing open. If it turns freely and smoothly with the door open but becomes stiff the moment the door is closed against the frame, the mechanism itself is fine and the door has moved slightly out of true — usually a hinge issue rather than anything wrong with the lock hardware.
This distinction matters because it changes the fix completely: lubricant will never solve an alignment problem, and an alignment adjustment won't fix a genuinely dry or worn gearbox. Diagnosing the wrong one wastes a call-out and delays the real repair.
What happens if you keep forcing it
The most common outcome of an ignored stiff lock is a snapped key, because the weakest point in the whole system is the thin brass or nickel-silver key blade, not the lock itself. The second most common outcome is a sheared gearbox cam, which turns a straightforward service call into a full mechanism replacement.
Neither of these failures happens without warning. Stiffness building over weeks or months is the door's way of asking for attention before something breaks rather than after.
A proper service visit versus a quick fix
A proper visit involves stripping and lubricating the cylinder, checking hinge tension and screw security, greasing the hook and roller mechanism along the door edge, and testing the lock through a full cycle with the door both open and closed under load.
This is deliberately more thorough than a five-minute spray-and-go, because the goal is to identify which of the two or three possible causes is actually responsible, rather than masking the symptom for another few weeks.
What we check first on arrival
On every stiff-lock visit we run the key through a full cycle with the door open, then again with it closed, timing how much extra resistance the closed position adds. That single comparison usually separates a dry cylinder from a genuine alignment problem before we've even opened a toolbox.
We also check the weatherstrip compression along the latch side, because an over-compressed seal — common after a door has been readjusted to fight draughts — can add just enough drag to make a healthy lock feel stiff without anything actually being worn.
How a stiff lock progresses toward failure
Stiffness doesn't stay constant; it accelerates. As dried lubricant turns to a gummy residue, that residue picks up dust and grit every time the key passes through, effectively turning the cylinder into a very slow grinding wheel on its own pins.
The realistic timeline we see across Cornwall properties is months, not years — a lock that's 'a bit stiff' in early autumn is often fully seized or key-snapping by the following spring, especially on coastal properties where salt air speeds up the lubricant breakdown considerably.
Coastal vs inland stiffness patterns
On exposed coastal doors, stiffness tends to build gradually across a whole season and affects the cylinder and gearbox roughly equally, because the salt-laden air degrades both at a similar rate. Inland properties more often show a lopsided pattern — the cylinder stays smooth for years while the gearbox stiffens first, usually because inland doors see more thermal movement than salt exposure.
Granite-built cottages present their own quirk: original openings are rarely perfectly square, so a door hung to compensate for that can develop stiffness that's really a very slow return toward the frame's natural (out-of-true) resting position.
Insurance and guarantee considerations
If your composite door is still within its manufacturer or installer guarantee, a stiff lock reported early is usually a straightforward warranty item — most guarantees explicitly cover premature hardware wear. Left until the lock seizes or the key snaps, some warranty terms treat that as consequential damage from neglect rather than a covered fault.
It's also worth knowing that a number of home insurance policies require locks to be in full working order for a burglary claim to stand, so a stiff lock you've been meaning to get looked at is not just an inconvenience — it's a small but real gap in your cover.
Timescales and getting parts on the day
Cylinder lubrication and hinge adjustments are always same-visit jobs. Where a full gearbox is needed, we carry the common Yale, ERA and Fuhr cases as standard stock, so the large majority of stiff-lock visits that do turn out to need a new gearbox are still resolved without a second appointment.
The exception is less common or older mechanisms, particularly on doors more than fifteen years old, where the exact case length has sometimes changed between manufacturer revisions — in that situation we'll measure precisely and order in, usually a two-to-four day wait.
Typical repair costs in Cornwall
| Work | Typical price | Notes |
|---|---|---|
| Cylinder clean and lubrication | £45-£75 | Often bundled with a hinge check |
| Full lock service (cylinder + gearbox + hinges) | £90-£150 | Recommended if stiffness has been present for weeks |
| Hinge adjustment only | £75-£110 | If stiffness only occurs with door closed |
| Gearbox replacement (if worn) | £180-£320 | Where lubrication alone hasn't resolved it |
Guide prices only — we confirm the cost after seeing the door.
When to call a professional
- Lubricant hasn't fixed it after 24 hours.
- You can hear grinding inside the door edge.
- The key has started to bend or you've had to use pliers.
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.
