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Barnet Lock Installation
Our Barnet engineers handle lock installation across Barnet and surrounding areas. Available day or night, 365 days a year; 20-minute average arrival. No surprises on price.
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All services in Barnet →On Victorian terrace properties the bore size of the existing mortice cut-out determines which replacement case will fit without widening the aperture. A case with a larger body than the existing bore means additional timber removal, which on a period door stile needs care to avoid splitting or weakening the lock rail. We confirm bore dimensions against the replacement case spec before committing to any additional chiselling.
On arrival
Measurement checklist: what we record on arrival
Four measurements are taken before any hardware comes off the van on a Barnet installation. A wrong-part revisit costs more than two minutes of careful measuring — we never skip this step.
| Measurement | Why it matters | Typical range |
|---|---|---|
| Stile width | Sets which security upgrade pathway case will physically fit without weakening the door at the lock rail. Upgrading from a 2-lever or 3-lever non-BS3621 mortice to a 5-lever certified case does not always require aperture extension — confirm the existing pocket dimensions against the replacement case body first. | 44 mm minimum for a full BS3621 mortice; narrower stiles may require a slimline case or a euro-cylinder alternative |
| Frame recess depth | Victorian terrace hardware upgrade: existing lock assessed for lever count and BS3621 compliance before replacement is specified. Partial replacement is costed separately if only one lock is below standard. | 13–20 mm on most residential timber; composite and UPVC frames can run shallower |
| Door thickness | Controls the cylinder length from face to face. A cylinder sitting proud of the outer face — even by 3 mm — creates a snap-attack leverage point that defeats anti-snap ratings. | 44 mm (standard timber), 54 mm (solid composite), 70 mm (hardwood or fire-rated) |
| Cut-out position | The distance from the door edge to the centre of the existing cut-out sets the backset. Extending an existing cut-out adds time and cost; fitting into the existing position is preferred wherever the hardware allows it. | 45 mm backset (most residential); 60–70 mm on commercial and period doors |
All four measurements are recorded on the job card and referenced in the installation certificate. If the measurements reveal a door that cannot accept the specified hardware without prep work, that is flagged and quoted before any tools come out.
Before quoting
Six door conditions that change the Barnet quote
Period property installations are priced around three variables: whether the existing mortice aperture needs enlarging, the BS3621 grade your insurer requires, and whether the door frame needs adjustment before the new hardware will operate cleanly. We assess the door on arrival and adjust the quote before starting any work. From £59 for a standard installation on a door in good condition.
- 01 Narrow stile
Greenwich and Lewisham Victorian terrace doors with a planted glazing bead on the inside face can appear to have a wider stile than is actually available for the lock case. The bead width is discounted from the stile measurement because it is surface-applied and cannot carry the case body screws; only the solid timber beneath the bead is counted toward the available depth.
- 02 Composite vs timber construction
Composite and UPVC doors use a different cylinder system from timber — euro profile with a multipoint gearbox rather than a mortice. Non-compliant hardware that appears functional may still be below the insurance schedule minimum — the lever count and BS3621 marking are the decisive criteria, not whether the lock operates smoothly. Confirming construction type before ordering avoids a wrong-part visit.
- 03 Existing cut-out dimensions
In Waltham Forest and Brent, many Victorian terrace doors retain original hardwood stiles that have been planed down in the past to cure a sticking problem. The stile face at the lock rail is measured top and bottom of the intended cut-out to detect any taper, and the narrowest reading governs the case selection to avoid the forend overhanging the stile edge on the thinner section.
- 04 Nightlatch position
Greenwich and Lewisham terrace doors that face east or west take direct sun through the year and can warp slightly at the leading stile edge, displacing the nightlatch backplate from true vertical. The backplate height is set with a spirit level against the face of the door, not the frame, so that the latch aligns correctly with the rim keep even if the door has developed a slight bow.
- 05 Frame condition
We assess the existing lever count the frame for squareness, settlement, and rebate wear before committing hardware to final position. A frame that is out of square or has a worn rebate needs addressing first — fitting a mortice into a moving frame produces a bolt that binds within months.
- 06 Letterbox clearance
Terrace doors in Southwark and Lambeth housing association stock sometimes carry a draught-excluding brush behind the letterbox flap that adds to the plate depth. The full depth including brush and backing plate is measured before a new lock position is confirmed; the combined depth must not overlap the mortice forend recess or the bolt pocket when the door is measured as-fitted.
Specification
Hardware compatibility: will this door accept BS3621?
Three questions answer most hardware compatibility conversations on a Barnet installation. We work through each on arrival and confirm the spec before any cutting or drilling starts.
- 01
Can this door accept BS3621?
A BS3621 5-lever mortice requires a minimum stile width (44 mm), a frame rebate to accept the forend, and sufficient door thickness at the lock rail. We check all three before specifying — a door that cannot take a BS3621 case without structural compromise will be quoted with a compliant alternative using a security upgrade pathway or existing lock lever count instead.
Partial replacement — replacing the mortice but retaining the nightlatch, or vice versa — is valid if the retained lock meets the insurance standard. Confirm both locks against the policy before quoting.
- 02
Cylinder size: 35/35 vs bespoke
Standard residential doors run 35/35 or 35/45 euro cylinders; composite and commercial doors often need bespoke lengths. We confirm the non-compliant hardware spec the cylinder run on site — face to face across the door leaf at the lock rail — and confirm the non-compliant hardware record specification before fitting. An oversized cylinder leaves the anti-snap collar exposed.
Anti-snap cylinders must be sized with the break-point inside the door face. A cylinder that is even 3 mm too long on the outside is vulnerable to a snap attack regardless of its anti-snap rating.
- 03
Nightlatch: rim vs mortice
Rim nightlatches surface-mount on the door face and require backplate clearance from the door edge and from any adjacent furniture. Mortice nightlatches fit into the door thickness and suit doors where the face is already occupied by a letterbox or knocker. The choice depends on the stile geometry confirmed at measurement, not a preference.
On insurance-graded installs both the primary lock and the nightlatch are noted on the compliance certificate. If the policy specifically names a rim nightlatch at a given standard, we confirm that against the door construction before the certificate is issued.
Completion
Handover and testing
The installation is not complete until every lock has passed a full function test on a closed door. On Barnet jobs we sign off three checks before handing back keys.
- Cycle test
Barnet and Enfield terrace doors with lime render on the frame jambs can shed small fragments into the bolt channel during the first few cycles. After the first five cycles the bolt pocket and keep mouth are inspected for debris and cleared before the remaining cycles are completed; this prevents render particles from scoring the bolt face on a new lock during the test period.
- Key issue
Keys are counted against the job card in front of the keyholder. Each key is labelled with the door reference it was cut for. No key leaves site unaccounted — if the agreed number is not present at handover, the job card flags the discrepancy before the engineer leaves.
- Written summary and certificate
Enfield and Barnet terrace properties managed by a block management company receive a handover pack that includes the lock certificate, the key schedule, and a one-page door condition assessment. The condition assessment notes any pre-existing defects observed — frame cracks, hinge wear, stile damage — so the managing agent has a baseline record that pre-dates the new installation.
Questions
Lock installation FAQ: Barnet
Period timber doors have their own sizing constraints: rebate depth and stile width are the primary fitting variables, and the answer to most installation questions starts there rather than with the lock model.
- Do I need to measure my door before calling?
- We measure on site so you do not have to. Tower Hamlets and Lambeth flat-conversion doors converted from room doors to entrance doors are particularly variable: the original door may have been made to a non-standard width, re-hung on new hinges, and had a letter aperture cut post-conversion. Each of these changes affects the lock specification, and only an on-site measurement gives a reliable result for all of them.
- Will the new lock look different from the original?
- On like-for-like replacements — same case position, same forend size — the external appearance changes only in terms of the new cylinder rose or escutcheon. On period doors where the original furniture is being retained, the escutcheon fit is checked for compatibility before the hardware is sourced. Where the new spec requires a different door face profile (e.g. switching from a mortice keyhole to a euro cylinder profile), we flag that on the booking call before the job date.
- How long does a Barnet lock installation take?
- A standard like-for-like cylinder replacement on a composite or UPVC door takes around 30–45 minutes including the full test cycle. A new BS3621 mortice installation on a timber door — where the existing cut-out is the right size — takes 60–90 minutes. If the door needs prep before the hardware fits (rebate adjustment, aperture extension, hinge correction) we agree the additional time and cost before starting. We do not proceed past the assessment stage without a confirmed price.
- What if the door needs repair work before the lock can be fitted?
- Paint build-up on Victorian terrace doors in Wandsworth and Haringey can reduce door clearance to the point where the door sticks in the rebate and the bolt cannot reach the keep. Before the new lock position is cut, the door edge clearance is measured on all four sides; where clearance is under 2 mm the door edge is eased with a plane and the paint build-up in the rebate is pared back to restore free movement.
Lock Installation in Barnet — FAQ
Common questions about lock installation in Barnet.
Can you install a lock on a brand-new door?
Period timber doors have their own sizing constraints: rebate depth and stile width are the primary fitting variables, and the answer to most installation questions starts there rather than with the lock model. Yes — this is one of our most common installation jobs in Barnet. Carpenters and joiners often hang the door and leave lock fitting to specialists. We measure the rebate, chisel for a BS3621 mortice case, fit the strike plate, and test through a full key cycle. Finished work looks factory-fit.
Do I need BS3621 on a new installation?
For external doors on Barnet homes with standard insurance — yes, almost certainly. BS3621 is the minimum most UK home insurers specify on final-exit wooden doors. We fit BS3621 as standard and issue written paperwork confirming the standard for your insurance file.
Can you keyed-alike multiple new locks?
Yes — if you want one key to open your front and rear doors, we supply keyed-alike cylinders on the most common profiles. Arrange at the survey stage so we bring matching parts. This works cleanly on UPVC euro cylinders and on certain mortice profiles.
We've just moved into a new-build in Barnet — do the locks already meet insurance standards?
Not always. Many Barnet new-builds come with entry-level euro cylinders on UPVC or composite doors that lack the TS007 3-star anti-snap rating, and sometimes a mortice case that predates BS3621 on the side door. We survey the whole property, identify any hardware gaps, and upgrade to compliant standards on the same visit — with a compliance pack for your insurer.
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