Guide

Need to Change the Lock on a uPVC Door Today? Barrel, Handle or Mechanism

You want new keys, or the key has started to fight you, and the lock on your uPVC door has to change. On most uPVC doors the part people mean by "the lock" is the barrel. It is held by a single screw, and once the correct replacement is in your hand, swapping it takes about five minutes.

The other two jobs sold under the same name, the handle and the multipoint mechanism, are different work. And what goes wrong most often is not the fitting but buying a barrel in the wrong size. This guide from Runcorn Locksmith covers the job, the measuring and the point to stop. If you would rather not do it yourself, call 01928 611001; emergency calls are taken day and night, every day of the year.

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Work Out Which of the Three Jobs You Are Doing

Three jobs hide behind the phrase "changing a uPVC door lock": the barrel, the handle, and the multipoint mechanism inside the door edge. Before any tool comes out, answer one question. Does the key turn but the door refuse to lock? Does the key not turn at all? Or does the lock work perfectly and you simply want new keys? Our guide to identifying which lock type you are looking at helps if the door hardware is unfamiliar.

The answers map onto the jobs like this:

You need new keys: the euro cylinder alone is likely all that needs to change. This is normally the easiest of the three.
The handle is loose or broken: a compatible handle set is needed, and that means extra measurements.
The locking points will not move: the gearbox or the multipoint mechanism may be at fault, and replacing it starts with identifying the exact system along the door edge.

If you are upgrading rather than repairing, the security rating is worth knowing about. TS 007 protection can be achieved with either of two combinations: a TS 007 Kitemarked three-star cylinder, or a TS 007 Kitemarked one-star cylinder combined with TS 007 Kitemarked two-star protective hardware. These ratings apply to the cylinder and protective hardware, not to the door as a whole.

The Five Minute Job: Changing the Barrel

The barrel is the part your key goes into. Locksmiths and suppliers call it a euro cylinder; almost everyone else calls it a barrel, and they are the same thing. It is the easy job because a single long screw through the faceplate on the door edge holds it in place. With that screw out, the barrel slides out sideways and the new one slides in. The mechanism, the handle and the door itself stay untouched.

People usually change the barrel for one of four reasons:

New keys after moving into a property.
A key that has been lost.
A worn barrel that needs jiggling before it will turn.
An upgrade to a rated cylinder.

One honest caveat before you start: the fitting is easy, and the buying is where most attempts go wrong. If you would prefer to hand it over, see our.

The Two Bigger Jobs: Handle and Mechanism

The handle and the multipoint mechanism are both bolted to the door rather than slotted into it, and each is a bigger undertaking than a barrel swap.

The handle: it comes off on two bolts that pass through the door and is a straightforward exchange, but the spindle size and the screw centres must match the door. That is why a handle chosen for its looks alone often will not fit.
The mechanism: this is the long metal strip in the door edge carrying the hooks and rollers. It can only come out with the door open and the faceplate screws removed, and the replacement must match a long list of dimensions, including the backset and the gearbox.

The mechanism is a measuring job before it is a fitting job, and it is the one most people pass to a locksmith. This guide does not set out a mechanism changeover.

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. A cylinder size is written as two numbers, such as 35/35 or 40/50. They describe the two sides of the central cam, which is itself 10mm wide, so a 35/35 cylinder measures 80mm end to end.

Where to Measure From, and the Five Millimetre Rule

Every euro cylinder measurement begins at the centre of the fixing screw hole, which sits in the middle of the cam.

Measure from that centre point to the outside face, then from the centre point to the inside face. Write the two figures down, outside first.
Round each one to the nearest 5mm, because cylinders are only made in 5mm steps. Tradelocks' own example: 43mm becomes 45mm, and 42mm becomes 40mm.
Label which side is which before the old cylinder leaves the door. An offset size such as 40/50 fitted backwards leaves the long side on the outside.

If nothing has been taken apart yet, you can take a first reading with the cylinder still fitted: measure from the centre of the keyhole to each face of the door, then confirm the figures once the barrel is out.

Why Copying the Old Barrel Can Make the Door Worse

Some well-known guides say to measure the barrel you removed; the suppliers who sell replacements warn against it, and they are right. If the barrel in the door is already too long, it stands proud of the handle plate, and buying the same size keeps it standing proud.

Too long: Lock Shop Warehouse recommends aiming for a protrusion of no more than 3mm, and the Suffolk Latch Company accepts a slight projection of 2mm to 3mm on each side of the handle plate. Anything beyond that is overhang, which leaves the cylinder easier to attack.
Too short: the cylinder sits recessed, the key can be awkward to use and the fixing screw may not line up.

So measure the door, compare the old barrel with it, and treat any mismatch as a fault to put right rather than a size to repeat. Our guide to the marks that tell you a cylinder is certified helps you choose the replacement.

Three trade suppliers agree on the method: Lock Shop Warehouse on the fixing screw as the reference point, the Suffolk Latch Company on the 10mm cam and the internal and external projections, and Tradelocks on rounding to the nearest 5mm and not copying the existing cylinder.

Sizing panel - Measure from the centre of the fixing screw hole, outside first, then inside. - Round each figure to the nearest 5mm. - Check the old barrel against the door; do not copy it blindly. An overhanging cylinder is why the euro cylinder becomes the weak point.

Collect the Tools This Job Needs

A barrel change calls for three things, and one of them is a ruler.

A long, thin screwdriver for the fixing screw, which sits deep within the faceplate on the door edge.
A steel rule or tape measure.
The new cylinder with its keys.

You might also need an allen key or small screwdriver if the handle has to come off, and a torch for a shadowy door edge. You will need a working key for the existing lock too. The fixing screw is longer than most people expect and easy to lose in a carpet, so decide where it will sit before you take it out.

A handle swap is a different list. It suits a fault confined to the handle set, spindle or handle springs, and it will not cure a failed gearbox or a misaligned door. Check the handle-to-cylinder centres, known as the PZ measurement, before the old set comes off, and keep the door open throughout.

Undo the Fixing Screw in the Edge of the Door

Open the door and find the metal faceplate running down its edge, roughly level with the keyhole. Follow these steps only if the door opens normally, and keep it open from start to finish. One screw, in line with the cylinder, runs through the faceplate into a threaded hole in the middle of the barrel. The screws securing the multipoint strip to the door are usually shorter than this fixing screw. Undo it completely and lift it out.

A note on handles. Guides disagree on whether the handle has to come off, and the honest answer is that it depends on the door. On most uPVC doors the screw can be reached with the handle still in place. The handle only needs removing where its plate or the escutcheon covers the screw or the face of the cylinder.

At this stage you should be holding one screw, and the cylinder should not yet have moved. Do not lever, force or drill anything to get further.

Line Up the Cam and Draw the Cylinder Out

The cylinder will not slide out until the small tab in its middle, the cam, is turned into line with the body. Insert the key, turn it a little, and draw gently on the key at the same time. Lock Shop Warehouse puts the turn at around 45 degrees to the left or right, and the direction varies between locks, so try one way and then the other rather than forcing it. Once the cam lines up, the cylinder slides out sideways towards you.

It will not budge, and the cam is aligned: the fixing screw is most likely still in, because nothing else holds the cylinder.
It is out: keep the old cylinder until the new one is fitted and tested.

A note for anyone eyeing the mechanism instead: it has to match the door's gearbox, faceplate and locking-point layout, and lookalikes are not necessarily interchangeable. A locked-shut door or locking points caught in the frame mean you must go no further.

Fit the New Cylinder the Right Way Round

Before the new cylinder goes in, confirm that the longer side faces into the house. Slide it in from the outside with its key turned to the same slight angle, so the cam clears the mechanism. Line up the threaded hole with the hole in the faceplate, which is easiest with a fingertip pressed on the cylinder face, then refit the long screw and tighten it without straining it.

Two checks decide whether the job has been done properly:

The cylinder should sit close to flush, standing proud by no more than about 3mm.
The key should go in and come out smoothly from both sides.

Some cylinders are directional, and Tradelocks notes these are marked to show which face goes outside. A cylinder that will not fit is the wrong cylinder; never file it, pack it or force it home. If the barrel was fine and something else was wrong, see whether the door needed a repair rather than a new barrel.

Test the Door Before You Walk Away

Test with the door open first, every single time. With the door wide open, lift the handle and turn the key both ways, and watch the hooks and rollers move in and out along the edge.

Operate the handle and key with the door open.
Close the door and repeat the whole sequence from outside.
Try every key in the set, from both sides, including the spares heading for a drawer.

The order matters. A cylinder that works with the door open but not with it shut is telling you about the door's alignment, not about the barrel, and our guide to a uPVC door that will not lock picks up from there. A new cylinder should turn smoothly without extra pressure. Keep the door open if the cylinder resists turning. Before closing or locking the door, check again that the part, measurements and fitting are correct. Do not assume a stiff new barrel just needs to bed in; forcing it can damage it or another part of the lock.

Stop and Call Someone If Any of This Applies

Everything above assumes a key that works and a door that opens. There are four points at which a locksmith becomes the shorter route: no working key, a snapped key, a door that will not open, and a cylinder that turns without achieving anything. Stop as well if the door cannot stay open and secure, if you cannot identify the correct part, or if any part needs force. The door, frame or whole locking system could suffer damage if you continue a repair you are unsure about, even when only a replaceable part needed attention. For any of these, an emergency locksmith is the faster answer.

If There Is No Key, or the Key Has Snapped

Yes, a cylinder can be taken out without its key, and no, this page will not explain how. A method that removes a cylinder without the key works on any door, including one that is not yours, and a locksmith publishing it openly is publishing it to everyone. The normal DIY route depends on a working key to line up the cam, so without one, professional removal is usually needed. What matters to you is the outcome: the old cylinder is destroyed in the process and replaced, so the job always ends with a new cylinder, which is the part you were going to buy anyway.

A snapped key is a different case and is often better news. If part of the key is still in the cylinder, the cylinder itself may be perfectly sound once the broken piece is out. Our guide to getting a snapped key out of a lock explains what happens next, and our broken key removal service handles it.

If the Door Will Not Open or the Key Turns and Nothing Happens

These two symptoms share one thing: neither is a barrel problem. Use the symptom as a pointer, not as a confirmed diagnosis.

The door will not open, though the key turns normally: this usually points to the mechanism or the alignment, and a new barrel will not touch it. The cylinder, handles and multipoint strip are normally removed with the door open, so do not follow the steps above while it is locked shut, and do not force or dismantle anything while the locking points are engaged in the frame.
The key turns freely and nothing happens, and the handle does nothing either: this usually points to the gearbox in the middle of the mechanism, a different part in a different place. Check compatibility before choosing a replacement gearbox: its connections to the locking strip, fixings, spindle arrangement, PZ centres and backset must all match.

A barrel bought to fix either of these is a part that was never at fault, and once it has been fitted in a door it is unlikely to be returnable. For a proper diagnosis, see a uPVC door that will not open and what goes wrong inside a uPVC lock mechanism.

Have It Changed Instead

If the size is unclear, the key is missing or the door is fighting you, we change uPVC cylinders and mechanisms across Runcorn. The steps above still stand; this is simply the alternative for anyone who would rather not.

Have ready: the door material, whether the key turns, and a photograph of the door edge and the handle.

There is no call-out charge at any time of day, and emergency calls are answered 24 hours a day, every day of the year. Technicians are [PROVIDER PACK: DBS check confirmation] and the business holds [PROVIDER PACK: public liability insurance details]. You are given a price on the call from what you describe, and if anything on site would change it, you are told before work starts. See also our lock replacement service.

Get a Price for a uPVC Lock Change: call 01928 611001.

uPVC Door Lock Questions

What do I need to change a uPVC door barrel?

A suitable screwdriver, a replacement cylinder in the correct size, and a working key for the lock already fitted. A ruler or tape is needed to measure first.

How do I find the fixing screw?

With the door open, inspect the metal faceplate along the door edge. The screw you want sits in line with the cylinder and is usually longer than the screws holding the multipoint strip.

Why will the old barrel not slide out?

Usually because the cam is not lined up with the cylinder body, or because the fixing screw is still in. Turn the key slightly, around 45 degrees either way, while drawing gently on it.

Can I just buy the same size as the barrel I took out?

Not without checking. The old barrel may have been the wrong size in the first place. Measure the door from the centre of the fixing screw hole and round to the nearest 5mm, aiming for no more than about 3mm standing proud.

Can I change the barrel without a key?

Not by the usual DIY method in most cases, because a working key is normally needed to line up the cam. Without one, professional removal is likely to be needed.

Should I change the barrel if the door is locked shut?

No. The standard steps assume the door is open, so do not follow them while it is locked shut. While the locking points remain engaged in the frame, do not apply force to the lock.

Is it the barrel, the handle or the mechanism?

Treat the symptom as a guide rather than a diagnosis. A key that will not go in or turn suggests the key or the cylinder. A key that turns while the locking points stay put points to the cylinder connection, the spindle, the gearbox or the multipoint mechanism.