Guide
How to Change the Lock on a uPVC Door: Barrel, Handle or Mechanism
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Work Out Which of the Three Jobs You Have to Do
The barrel, handle set and multipoint mechanism within the door edge are three separate replacement jobs. Sort the symptoms before reaching for tools: is the key unable to turn, does it rotate while the door stays unlocked, or is everything working and you simply need fresh keys? That distinction helps establish which part needs attention.
Handle and Mechanism: The Two Bigger Jobs
Damaged or slack handles require a compatible replacement set. Measure the fixing positions, spindle and handle-to-cylinder centres before ordering. A similar-looking set can still be unsuitable for the existing gearbox.
If the locking points do not move, the fault may involve the gearbox or multipoint mechanism. Identifying the complete system along the edge comes before replacement. A qualified locksmith can undertake that work; removing the mechanism can leave the entrance unsecured.
Changing the Barrel: A Five Minute Job
For a change of keys, the euro cylinder may be all that needs replacing. This is generally the simplest task. Locate its retaining screw on the faceplate and establish the required size and outward-facing end. Neither a matching brand nor a familiar shape confirms suitability.
Two arrangements provide TS 007 protection: a TS 007 Kitemarked cylinder rated three stars, or a TS 007 Kitemarked cylinder rated one star together with TS 007 Kitemarked protective hardware rated two stars. These ratings apply at component level, covering the cylinder and protective hardware without certifying the complete door or multipoint mechanism. Anti-snap wording alone proves no recognised testing.
Proceed only with a safely opening door and no force. Check operation after fitting and seek qualified help if problems remain.
Measure the Cylinder Before You Buy Anything
Measure from the centre of the fixing-screw hole out to each end, and never assume the barrel already in the door is the right size. Euro cylinders are sold by two numbers, such as 35/35 or 40/50, one for each side of the central cam. The cam is 10mm wide, so a 35/35 cylinder is 80mm long overall, while a 40/50 has 40mm on one side and 50mm on the other.
Where to Measure From, and the Five Millimetre Rule
Open the door and find the retaining screw in the metal faceplate, usually level with the cylinder. From the centre of that screw, measure to the outside face of the external handle or escutcheon, then to the inside face of the internal furniture. Write the figures down separately and mark which faces outside. Cylinders come in 5mm steps, so 43mm points to 45 and 42mm to 40, but check the available sizes and the finished position before rounding.
How Copying the Old Barrel Can Make the Door Worse
A fitted cylinder that already stands proud stays proud if you buy the same size again. Aim for no more than about 3mm beyond the handle plate, with 2mm to 3mm each side as the accepted range. Too short is also a fault: the barrel sits buried, the key is awkward and the screw may not line up.
Sizing panel: zero at the screw-hole centre; 5mm steps; no more than about 3mm proud. Before ordering, confirm both readings, the outside end, key or thumbturn inside, and how the face meets the handles. This is why an overhanging cylinder is the weak point.
Undo the Fixing Screw Set in the Edge of the Door
This first step is simpler than most people expect. With the door standing open, look at the metal faceplate running down its edge; about level with the keyhole sits the cylinder retaining screw. It is longer than the faceplate screws around it because it reaches through into a threaded hole at the centre of the barrel.
- Check it is the screw in line with the cylinder, not a strip fixing.
- Remove it completely with a suitable screwdriver.
- Put it somewhere it cannot roll away.
- Leave the multipoint strip screws untouched.
Use the correct screw supplied or specified for the replacement if the original is damaged or unsuitable for the new cylinder.
Handles: on most uPVC doors they can stay fitted. If a handle plate or escutcheon hides the screw or the cylinder face, loosen that plate's own fixings rather than prising it.
You should end this step with a single screw out and the cylinder exactly where it was.
Collect the Tools Needed for This Job
Fewer tools than you might expect: three for a barrel change, and one is simply something to measure with.
- A thin screwdriver with enough shaft to reach the screw recessed into the faceplate
- A steel tape or rule
- The replacement cylinder and its set of keys
Bring the key that operates the current lock, since the old barrel is released with it. If needed: an allen key or small screwdriver where the handle has to be taken off, and a torch where the door edge is dim. For a handle replacement, the extra items are a compatible handle set, the correct spindle, the right fixing screws and a suitable screwdriver.
A drill has no place here; there is no hole to make. The fixing screw is the item most often lost, being longer than people imagine and quick to vanish into carpet, so put a small tray down first.
Make Sure the New Cylinder Is Fitted the Right Way Round
One question comes first: which way round does this barrel go? On an offset cylinder, the longer end must face into the house, and if it has a thumbturn, that sits inside as well. Directional cylinders carry a marking that identifies the outside face, which makes the check easy.
Turn the new key slightly so the cam lines up, then slide the cylinder into the door from the outside without pushing. A little movement of the key settles it the last few millimetres. Should it catch, take it back out and recheck the size, the direction and the cam. Use a finger on the face to bring the threaded hole into line with the faceplate opening, insert the correct screw and tighten it until the barrel holds firm, without straining it.
Confirm two things before moving on: - No movement in the door, a correct fit within the handle plates and no more than about 3mm standing proud outside. - Smooth key entry, turning and removal on both sides, loosening the screw and rechecking if tightening caused stiffness.
Never file, pack or force a cylinder to make it fit; a cylinder that does not fit is the wrong one, and you might also consider whether the door needed a repair rather than a new barrel.
Line Up the Cam and Draw Out the Cylinder
Turning the cam is the step that most guides skip, and it is why so many barrels seem welded in place. The cam is the small tab at the centre of the cylinder, and it must line up with the body before anything slides. Put in the working key and turn it slightly, around 45 degrees, in whichever direction your lock needs; try one way, then the other, gently. Keeping the key at that angle, hold the cylinder where you can and draw it out towards you, adjusting the key a little if it drags.
If it will not come: 1. Recheck that the fixing screw is completely removed and the cam is aligned, as those are the usual causes. 2. Check for a handle plate holding it and for damage or distortion to the barrel. Stop if force would be needed.
At no point should the key take a hard pull or be used as a lever. Keep the old barrel until the new one is fitted and proven.
Test the Door Before You Walk Away
Test it open before you test it shut, and do that every time you fit a cylinder. Here is the sequence.
- With the door open, insert and remove the key from both sides, or turn the thumbturn, then lift the handle and lock as normal. Hooks, rollers and bolts should extend and retract along the edge; if there is a trigger, use the manufacturer's test method.
- Retract every locking point, bring the door gently to the frame without locking, and confirm it closes naturally with the latch meeting the keep.
- Shut it fully and operate the handle and key, with no force, from inside and from outside.
Why that order? Because a lock that works with the door open but not with it closed is reporting on the door, its hinges or its keeps, not on the barrel you just fitted. A lock that is stiff while the door is still open points back to the cylinder: recheck its size, fitting and compatibility before the door is used. A new part should never need excess pressure, and assuming it will wear in only invites damage. The final check is the keys, every one of them, tried from both sides, spares included.
If Any of This Applies, Stop and Call Someone
This guide only holds while you have a working key and a door that opens. Outside that boundary are four stopping points: the key is missing, the key has snapped, the door is locked shut, or the cylinder turns and nothing happens. If the door cannot be kept open and secure, the component cannot be identified or a part needs force, carrying on risks damage to the door, the frame or the whole lock.
If There Is No Key or the Key Has Snapped
There are ways to remove a euro cylinder without its key. We will not describe them, here or anywhere on this site, because a technique that opens your door opens any door. In practice the cylinder is destroyed during removal and a new one goes in, so the end result is the part you meant to buy. A broken key is different: the cylinder itself may be perfectly sound once the broken piece is out.
If the Key Turns and Nothing Happens, or the Door Will Not Open
Neither is a barrel fault. A locked-shut door with a normally turning key suggests the mechanism or alignment. A handle or key that moves while the hooks stay engaged suggests the gearbox. Do not force either.
Damaged doors after a break-in, fire doors and communal or managed flat entrances also need a professional. Note whether the door is open, closed or locked shut, whether the property is secure, and any markings, then contact.
Get It Changed Instead
Whether you have finished the job or decided not to start it, HD Locksmiths Bournemouth can change uPVC cylinders and mechanisms across Bournemouth when the size is uncertain, the key has gone or the door is resisting. Plenty of people fit their own barrel, and the guide above holds; this is the alternative. Calls are free of any call-out charge, whatever the hour, and emergency calls are answered around the clock all year. The price is given on the call, based on your description.
Useful to have: the door material, a note on whether the key turns, and a photograph of the edge and the handle.
Get a Price for a uPVC Lock Change: 01202 935089
Or book a uPVC lock change with HD Locksmiths Bournemouth, and see our lock replacement service for more.
uPVC Door Lock Questions
Can I change a uPVC door lock without the original key?
The normal DIY removal procedure is generally unsuitable when every working key is missing. A key is normally used to set the cylinder cam in line; removal without it may require professional assistance. Access with an open door is usual when taking out the multipoint strip as well as the handles and cylinder. Do not follow routine replacement directions on a locked, closed door, and avoid forcing or dismantling the lock while the locking points remain engaged with the frame.
Can I change a uPVC door lock if the door will not open?
A door locked shut needs attention before standard replacement work can begin. Normal removal of the cylinder and multipoint strip, plus the handles, is carried out with the door open. Do not force or take apart the lock while its locking points remain engaged in the frame. For cylinder removal, the usual DIY approach generally needs a working key to position the cam; lacking a key, removal may require a qualified locksmith.
How do I know whether the cylinder or gearbox has failed?
An inspection is needed to establish the cause, with symptoms helping to choose what to examine. Failure to insert or rotate a key could concern that key or its cylinder. If it rotates while the locking points do nothing, check the gearbox and multipoint mechanism, plus the spindle and cylinder connection.
Can I replace the barrel without changing the multipoint mechanism?
Yes, replacing a euro cylinder on its own is normally possible. Check that the handles, gearbox and locking points all work correctly. With those parts functioning, a barrel change may be sufficient if the aim is to obtain new keys or improve the lock's security.
Do I need to remove the handles to change a euro cylinder?
Usually, the handles can stay in place. For most euro cylinders, removal involves undoing the retaining screw and using the key to bring the cam into line. If the handle plates or protective furniture block the cylinder, those parts may need to be loosened.
Are all uPVC door handles the same size?
No, matching uPVC handles involves more than their overall size. The PZ centres, backplate dimensions, fixing layout, spindle arrangement and operation all vary between sets. Record the existing set's measurements before ordering. Door thickness can influence the necessary lengths of both the screws and the spindle.
Why does my uPVC door lock work when open but not closed?
The frame contact is a likely place to investigate. Resistance where the locking points and door meet it commonly explains this symptom. Possible reasons are hinge wear, a drop in door position, or hooks, bolts and a latch that no longer meet their keeps in alignment.
Can I replace only the gearbox in a uPVC door lock?
Yes, but the replacement gearbox must match the backset, spindle arrangement, fixings, PZ centres and locking strip connections. Check the rest of the mechanism too. If its strip or any other locking points are worn or damaged, replace the complete mechanism.
Can I replace a multipoint lock with a different brand?
Another brand is an option if the replacement mechanism is designed for compatibility. The gearbox, locking point locations, faceplate, operating method and dimensions must all match the door. Where the locking points differ, the keeps fitted to the frame may need changes as well.
What happens if I fit the wrong-size euro cylinder?
Too long may mean too exposed; too short may mean awkward key use. Extra cylinder length can project past the protective furniture outside, leaving more visible. Insufficient length may leave the cylinder sitting too deeply. Before ordering, measure its inside length separately from its outside length.
Do I need to replace the complete lock after losing my keys?
A cylinder change will usually suffice instead of a complete lock replacement. Where the lost keys operate a euro cylinder, with every other locking component functioning correctly, renewing it should stop the keys working at the door. Also assess any additional locks with keys to establish whether they require attention.
Why is the new uPVC door handle still drooping?
The gearbox or fitting may be involved, as well as the handle components. Possible causes include handle springs, the spindle, alignment of the fixings and the internal gearbox. Check the measurements and installation again with an open door. A replacement handle set must not be assumed to fix gearbox trouble.