Mortice Lock Replacement Sheffield 5 Lever BS3621 Locks
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Worn, stiff or uninsurable mortice lock on a wooden door? We match the case size, fit a 5 lever BS3621 deadlock or sashlock and test it against the keep before we leave.
BS3621 Kitemarked locks
The British Standard wording most home insurance policies use for exit doors
Case size matched
2.5 inch or 3 inch bodies so the existing mortice pocket is reused
Deadlock or sashlock
Bolt only, or bolt plus a handle operated latch, to suit the door
Old timber doors handled
Victorian and stone house doors packed and trued so the bolt throws fully
Our mortice lock replacement service in Sheffield swaps worn or underspecified locks on timber doors for new 2, 3 or 5 lever mortice locks, including 5 lever BS3621 deadlocks and sashlocks from £75, with a locksmith usually at your door within 25 to 45 minutes. A plain 2 lever lock starts from £25 and the price is confirmed on the phone before any work begins.
Below we explain what the lever count and the Kitemark actually mean, how to read the faceplate on your current lock, and why the case size matters on older Sheffield doors.
What makes a lock a mortice lock
A mortice lock sits inside a rectangular pocket cut into the edge of a wooden door, so only the faceplate and the keyhole show. That is different from a nightlatch, which is screwed onto the inside face of the door and works with a rim cylinder. Many front doors in Sheffield have both: a latch for everyday use and a mortice deadlock below it for when the house is empty.
Because the lock body is buried in the timber, a good mortice lock is hard to attack from outside. The trade off is that the door around it has to be sound. A split stile or a pocket chewed out by previous fittings weakens even the best lock, which is why we check the timber before recommending anything.
If your problem is the nightlatch rather than the deadlock, our page on Yale nightlatch replacement covers that side of the door.
Sashlock or deadlock: which one is in your door?
Mortice deadlock
A single square bolt thrown by the key. There is no handle and no spring latch, so the door is held shut by something else during the day, usually a nightlatch or a rim latch.
Typical on front doors paired with a Yale style latch.
Mortice sashlock
A key operated deadbolt plus a sprung latch worked by lever handles. One lock does both jobs, which suits back doors and kitchen doors where you want handles.
Typical on back doors of terraces and semis.
Bathroom and internal mortice locks
Lightweight 2 lever or thumbturn privacy locks with no real security role. They fail from wear rather than attack.
Cheap to swap and never needed for insurance.
Replacing like for like keeps the keyhole and spindle in the same place, so the existing handles and escutcheons still line up. Changing from a deadlock to a sashlock is possible, but it means drilling for a spindle and fitting handles, which we price separately.
2 lever, 3 lever and 5 lever mortice locks compared
Levers are the small flat plates inside the lock that the key has to lift to exactly the right height. More levers mean more possible key combinations and more resistance to manipulation. The lever count is usually stamped on the faceplate.
| Lock | Where it belongs | Starting price to change |
|---|---|---|
| 2 lever mortice | Internal doors, store rooms, low risk outbuildings | £25 |
| 3 lever mortice | Older back doors and internal doors; not enough for a final exit door on most policies | £40 |
| 5 lever mortice | External doors where a Kitemarked lock is not demanded | £60 |
| 5 lever BS3621 mortice | Front and back exit doors; the usual insurance requirement | £75 |
A 5 lever lock is not automatically a BS3621 lock. Some budget 5 lever locks lack the drill protection, bolt length and other features the standard needs. If a policy asks for BS3621, only a Kitemarked lock satisfies it. Our full locksmith price list shows every lock type side by side.
How to check your mortice lock is BS3621
Open the door and look at the metal faceplate on its edge. You do not need to remove anything.
- Look for the Kitemark. A small heart shaped BSI logo next to the text BS3621 is the clearest sign. Older locks may show BS3621:1998, newer ones BS3621:2007 or later.
- Count the levers. Many faceplates read 5 LEVER. If you see 2 or 3, or nothing at all, it will not meet the standard.
- Check the bolt. With the door open, lock it. A compliant deadbolt projects about 20mm, noticeably further than a cheap lock.
- Check the keep. On the frame, a boxed keep that encloses the bolt is better than a flat plate. A loose or split keep undoes much of the lock’s strength.
If the faceplate has been painted over, which is common in older houses, we can identify the lock on arrival. You may also see BS8621 on some locks: that version can be opened from inside with a thumbturn, which is useful where people need to leave quickly without hunting for a key.
Case sizes, backsets and why measuring matters
UK mortice locks mostly come in two case depths: 2.5 inch (about 64mm) and 3 inch (about 76mm). The backset, the distance from the door edge to the centre of the keyhole, is roughly 44mm on a 2.5 inch lock and 57mm on a 3 inch lock. Sashlocks also have a fixed distance between the spindle and the keyhole, which decides whether the old handles fit.
Matching all three measurements means the new lock drops into the existing pocket with no fresh cutting. Get one wrong and you end up with a keyhole that does not line up with the escutcheon, or a pocket that needs chiselling deeper. Narrow stile glazed doors sometimes need a shallower case altogether.
A quick photo of the faceplate and the inside of the door sent before we visit usually lets us bring the right body first time. Our general lock replacement service covers nightlatches, cylinders and other lock types if more than the mortice needs changing.
Mortice locks and your home insurance wording
Many home insurance policies say something like: final exit doors must be secured by a five lever mortice deadlock conforming to BS3621. Some accept an equivalent multipoint lock on uPVC doors instead, and some say nothing at all. The only way to know is to read the security section of your own policy.
Where the wording is there, a claim after a burglary can be reduced or refused if the lock does not match. That is the main reason people ask us to swap a perfectly working 3 lever lock for a Kitemarked one. While we are there, it costs little extra to make sure the keep on the frame is fixed into solid timber, since an insurer will not care about the lock if the frame splits around it.
Landlords
Rental policies often repeat the BS3621 requirement. If you are changing locks between tenancies anyway, our landlord locksmith service can upgrade and rekey in the same visit.
Mortice lock replacement on Sheffield's older timber doors
The city’s stone and brick terraces still have plenty of original or early replacement timber doors. Around Walkley and Crookes the back door often opens onto a steep yard or shared passage, and it is frequently the one with the weakest mortice lock. In the larger stone villas of Nether Edge and Ranmoor, heavy front doors may carry old locks with oversized cases that no longer match modern stock.
Timber moves. In a damp Sheffield winter a door can swell enough that the bolt no longer meets the keep cleanly, so the key feels stiff or will only turn when you push the door. Replacing the lock alone does not fix that; the keep may need moving or the door easing. Where the frame or door itself is damaged, our door repair team can sort it in the same visit.
For oversized or unusual old locks we either source a modern lock that fits the existing pocket, or pack and re-cut neatly so the new case sits square.
What a mortice lock change involves
Most swaps take under an hour per door. We remove the old lock through the edge of the door, check the pocket, fit the new body, then test it with the door open and closed, from both sides, several times. Spare keys come with the new lock, and you get all of them.
If a key has snapped inside the old lock, we remove it first; see our page on broken key extraction. If the lock has simply jammed and the door is shut, we open it non-destructively where possible before replacing anything. More options are listed on our locksmith services page.
Mortice lock replacement prices
Starting prices from our published list; the exact lock and total are agreed on the phone before we attend.
| Service | Starting price | Notes |
|---|---|---|
| 2 lever mortice | from £25 | Internal doors and low security uses |
| 3 lever mortice | from £40 | Older internal and secondary doors |
| 5 lever mortice | from £60 | External doors without a Kitemark requirement |
| 5 lever BS3621 mortice | from £75 | Kitemarked deadlock or sashlock for insured exit doors |
| Lock rekeying | from £25 | Where the lock body is sound and only new keys are needed |
| Lock repair | from £55 | Freeing and servicing a stiff or jammed mortice lock |
Starting prices, confirmed on the phone before any work begins. See the full Sheffield locksmith price list.
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