Patio Door Specialist
A sliding door carries its whole weight on four small wheels
Every other door in your house hangs from hinges screwed into a frame. A sliding patio door does not hang from anything. A panel of double glazing weighing somewhere between sixty and a hundred kilos sits on four rollers the size of a two pence piece, running along an aluminium track set into the threshold. That is the entire arrangement, and it is why patio doors fail from the bottom upwards rather than from the lock inwards.
The wear is relentless because of where the track sits. It is at floor level by a garden, so it collects grit, leaf mould, sand off boots and whatever the mower throws up. That debris grinds into the roller bearings every time the door moves. The rollers flatten, the door starts to drag, and people respond by shoving harder — which loads the frame, pushes the panel out of square, and eventually stops the hook lock lining up with its keep at all.
Which is the part worth understanding before you call anybody. When a patio door will not lock, the lock is very rarely the problem. The panel has dropped a few millimetres onto worn rollers, so the hooks are meeting the keep low. Replace the lock and you have a new lock that still will not engage. Lift the door back to its correct height and the original lock usually works perfectly again.
How We Get a Sliding Door Running Again
When a patio door stops locking, the lock is usually innocent. The panel has dropped onto worn rollers and the hook is meeting the keep too low, which is a lifting job rather than a lock job.
Rollers, Tracks and the Weight of Glass
Rollers are consumable parts and most patio doors are on their originals. When they flatten, the panel sits low and drags. Replacing them means taking the weight of the glass off the track safely, which is the part that needs two people and proper lifting gear rather than enthusiasm. While the panel is out we clean and check the track, because dropping new rollers into a scored, packed track simply wears them out again within a couple of years.
uPVC and Composite DoorsDoors That Can Be Lifted Out
The weakness unique to sliding doors is vertical. Because the panel rests on rollers rather than hanging on hinges, an older door with worn wheels and no anti-lift protection can sometimes be lifted up and out of its track from the garden side, with the lock still engaged. Anti-lift blocks, correctly adjusted rollers and a good hook lock together remove that route entirely, and they cost very little compared with what sits behind the door.
Upgrade the LockPatio Locks, Handles and Keeps
Sliding doors use their own hardware: a hook lock that swings out into a keep rather than a bolt that shoots forward, and slim inline handles that take real force when the door is dragging. Hooks wear round, keeps work loose, and handle spindles shear. All three are replaceable individually, which is worth knowing because a patio lock failing does not mean the whole door has to be reglazed or replaced.
If the Mechanism Has FailedWhy the Track Matters More Than the Lock
- We check the rollers before the lock — a dropped panel and a failed lock look identical from the inside, and only one of them is expensive.
- Glass handled properly — taking a sealed unit out of a track is a two-person lift with the right gear, not something to improvise on a patio.
- Tracks cleaned and checked, not just topped up — new rollers dropped into a packed, scored track are worn out again inside a couple of years.
- 180-day warranty on locks, lifetime on keys — with the exact rollers and lock named on the invoice, which matters when parts are needed again.
Our Process - What Happens When You Call
- Tell us how it slides, not just how it locks. Dragging, grinding, catching halfway, or needing a shoulder behind it. The way a door moves tells us far more than the way it locks.
- Say what the door is made of. uPVC, aluminium or timber, and roughly how old. Aluminium patio systems from the seventies and eighties take different parts to a modern uPVC slider.
- Diagnosed with the panel on the track. We measure the drop, check the rollers and look at where the hook is meeting the keep before quoting anything.
- Lifted, adjusted and tested repeatedly. New rollers or an adjustment, the track cleaned, then the door slid and locked over and over until it runs and latches without any help.
Why Choose N1 Locksmiths?
You speak to the person doing the job
Describe how the door slides and the right rollers, hook locks and keeps are on the van before it leaves Holloway Road.
Priced on the call, before we travel
An adjustment, a set of rollers and a full patio lock replacement are three different prices, and you hear which is likely first.
Two-person lifts where the glass demands it
A sealed patio unit is heavy and awkward. We bring the help and the equipment rather than risking your glass or your threshold.
180-day warranty on locks, lifetime on keys
Every lock and every roller set we fit is guaranteed, with the parts named on the invoice.
Security checked while we are there
Anti-lift protection and the state of the hook are looked at as a matter of course, because this door faces your garden.
15–30 minutes across N and NW
Worked from Holloway Road, so a patio door that will not lock does not have to stay that way overnight.
Slide it slowly and listen
Before you call, run the door gently from one end to the other and pay attention to what you can hear and feel. A grinding or rumbling noise means the rollers have gone. A door that runs sweetly but stops short of locking means the panel has dropped. A door that catches at one specific point usually has something packed into the track. Those three sounds point at three different jobs and three different prices, so describing what you heard gets you a realistic figure before anybody travels — typically arriving within 15–30 minutes across the N and NW postcodes.
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A patio door is rarely the only thing on the list at the back of a house. These are the jobs most often booked alongside it — a back door that has dropped the same way, folding doors onto the same garden, or a rear entrance brought onto the same key as the front.
Areas We Cover Across London
We repair sliding patio doors across N1 to N22 and NW1 to NW11 from 37 Holloway Road in N7, and this job maps almost exactly onto where the gardens are. The rear extensions built across Highbury, Canonbury, Barnsbury and Hampstead through the seventies and eighties nearly all came with aluminium sliders, and a great many are still on their original rollers half a century later. Family houses towards Finchley, Golders Green, Barnet and the NW11 roads tend to have later uPVC sliders onto larger gardens, where the security side matters more — rear access from a side gate or an alley is what makes a garden-facing door worth protecting properly rather than simply making it slide again.
FAQs – Patio Door Specialist
My patio door is really hard to slide. What causes that?
Worn rollers and a dirty track, in that order, and they feed each other. Grit packs into the track, grinds the roller bearings flat, the panel sits lower and drags harder, which grinds them further. Cleaning the track helps briefly, but once the rollers have flattened they need replacing. It is a straightforward job and it transforms how the door feels.
The door slides but the lock will not engage. Is the lock broken?
Usually not. The panel has dropped a few millimetres onto worn rollers, so the hook is arriving below the keep. Fitting a new lock to a dropped door gives you a new lock that also will not engage. Getting the panel back to the right height, either by adjusting the rollers or replacing them, normally brings the original lock straight back into use.
Can patio door rollers actually be replaced, or do I need a new door?
Replaced, in the large majority of cases. Rollers are consumable parts and most doors are still on the originals fitted decades ago. Replacing them means lifting the panel off the track safely, which needs two people and the right equipment, but the door itself, the frame and the glass all stay exactly where they are.
Is it true a sliding door can be lifted out of its track?
On older doors with worn rollers and no anti-lift protection, yes, and it is the weakness specific to sliding doors. Because the panel rests on wheels rather than hanging on hinges, there is upward movement available. Anti-lift blocks and correctly set rollers remove that movement, and they are inexpensive compared with everything behind the door.
Do you work on old aluminium patio doors as well as uPVC?
Yes, and they come up constantly in houses that were extended in the seventies and eighties. Aluminium sliders use their own patio lock patterns and roller assemblies, some of which are no longer made, so occasionally we fit a modern equivalent rather than a like-for-like part. We tell you which on the doorstep rather than after.
What is the difference between this and bi-folding doors?
A slider has one or two panels running past each other on a bottom track. A bi-fold has several leaves that concertina, running on a top or bottom track with shootbolts at each leaf. The faults are different and so are the parts, so if yours folds rather than slides, our bi-folding door page is the one you want.
The handle turns but nothing happens. What has gone?
Most often the spindle has sheared or the hook itself has worn round, both of which are common on a door that has been dragging for years and taking force through the handle. Both are replaceable on their own. It is worth mentioning the make on the phone if you can see it, because patio handles are not all interchangeable.
I am locked out through my patio door. Can you open it?
Usually, and non-destructively wherever the mechanism allows. Sliding doors have their own opening techniques and they are not the same as a front door, which is exactly why it is worth telling us it is a patio door when you call rather than just saying you are locked out.
Should I add a secondary lock to my patio door?
It is worth considering, particularly on a ground-floor door facing a garden with rear access. Foot bolts, secondary patio locks and anti-lift blocks all add a second point of restraint for very little money. On a door that is already sound they are quick to fit, and they matter more than upgrading a lock that is working fine.
How long does patio door work take?
An adjustment and a track clean is usually under an hour. A set of rollers, including lifting the panel out and refitting it, is typically ninety minutes to two hours. A patio lock or handle change on its own is quicker. We would rather give you an honest window than promise thirty minutes and overrun.
Is it worth repairing an old patio door?
Very often, yes. A door with tired rollers and a worn hook can be running smoothly and locking securely again for a fraction of what replacing the whole unit costs, and the glass and frame are frequently in perfectly good order. Where the frame has corroded or the sealed unit has failed, we will say so plainly rather than sell you a repair that postpones the inevitable.