Yes — replacing a euro profile cylinder is one of the more DIY-friendly lock jobs a homeowner can tackle. It doesn't involve any restricted trade work, requires only basic tools, and can make a real difference to your home's security. That said, getting the sizing right and choosing a quality cylinder are the keys to success.
What Is a Euro Profile Cylinder?
A euro profile cylinder (also called a euro cylinder or DIN cylinder) is the oval-shaped lock insert found in many modern doors — particularly uPVC, aluminium, and some timber doors. It's the part that accepts your key and operates the latch or deadbolt. The cylinder slots into the door hardware and is held in place by a single fixing screw accessed from the edge of the door.
Because the cylinder is a self-contained unit, you can swap it out without replacing the entire lockset — making upgrades relatively simple.
Is This Restricted Work in New Zealand?
No. Replacing a euro cylinder is not restricted trade work under New Zealand law. Unlike electrical work (regulated by the Electrical Workers Registration Board) or gas and plumbing work (regulated by the Plumbers, Gasfitters and Drainlayers Board), locksmithing has no statutory licensing requirement in NZ for standard residential lock replacement. A homeowner can legally replace their own cylinder.
However, if your door is part of a fire-rated assembly or a commercial tenancy, there may be compliance considerations — check with your local council or a qualified locksmith if you're unsure.
Choosing a Higher Security Cylinder
Not all euro cylinders are equal. When upgrading, look for these features:
- Anti-pick pins — resist manipulation by picking tools
- Anti-drill protection — hardened steel inserts or anti-drill pins protect the core
- Anti-bump resistance — bump keys are a common break-in method; quality cylinders resist this
- Key control — restricted keyways mean keys can only be cut by authorised locksmiths
- Snap resistance — a critical feature in NZ and the UK; cylinder snapping is a known attack method where the exposed portion of the cylinder is broken off. Look for cylinders marketed as anti-snap
Well-regarded brands available in NZ include Mul-T-Lock, ASSA Abloy, Lockwood, and Kaba. Look for cylinders that meet EN 1303 (the European standard for lock cylinders) — check the manufacturer's documentation for the security grade rating. You can check standards information through Standards NZ.
Getting the Right Size
This is the most critical step. Euro cylinders are measured in millimetres from the centre of the fixing screw hole to each end — written as, for example, 35/35 (symmetrical) or 35/45 (asymmetrical, where the longer side is on the outside).
How to measure your existing cylinder:
- Open the door and locate the fixing screw on the edge of the door — remove it.
- Insert your key, turn it slightly to release the cylinder, and slide it out.
- Measure from the centre of the screw hole to the outside face, then to the inside face.
- Note the total length (e.g. 70 mm = 35/35).
| Measurement | What it means |
|---|---|
| Outside (e.g. 35 mm) | From screw hole centre to exterior face |
| Inside (e.g. 35 mm) | From screw hole centre to interior face |
| Total (e.g. 70 mm) | Overall cylinder length |
A cylinder that's too long will protrude and be vulnerable to snapping. Ideally, the cylinder should sit flush or no more than 3 mm proud of the door furniture on the outside.
Step-by-Step: How to Replace the Cylinder
What you'll need
- Flathead and Phillips screwdrivers
- Your new cylinder
- The existing key (to release the old cylinder)
Steps
- Open the door and keep it open throughout — don't lock yourself out mid-job.
- Remove the fixing screw from the edge of the door (usually a single screw in the centre of the latch plate).
- Insert the old key and turn it slightly (about 10–15 degrees) to align the cam inside the lock body.
- Slide the old cylinder out — it should pull straight out with gentle pressure.
- Insert the new cylinder in the same orientation, turning the key slightly to align the cam as needed.
- Replace the fixing screw — don't overtighten, as this can stress the cylinder.
- Test thoroughly — lock and unlock from both sides before closing the door.
Security Tips for NZ Homeowners
- Cylinder snapping is a real threat — always choose an anti-snap cylinder for exterior doors.
- Consider pairing your new cylinder with door reinforcement hardware such as a security escutcheon plate, which covers and protects the cylinder.
- BRANZ provides research and guidance on building security and performance that may be useful for broader home security upgrades.
- If you're a landlord, note that the Healthy Homes Standards include requirements around draught stopping and security — ensure any lock changes don't compromise tenant access obligations.
When to Call a Professional
While this is a manageable DIY task, call a qualified locksmith if:
- The old cylinder is damaged, seized, or won't release — forcing it can damage the door or lock body.
- Your door uses a multipoint locking system — these can be more complex to work with.
- You're unsure about sizing or the door is a fire door or commercial entry.
- You want key control across multiple locks — a locksmith can key cylinders alike or to a master key system.
- The job involves a rental property and you need documentation for compliance purposes.
A qualified locksmith can also assess your whole door's security, not just the cylinder. You can find trusted local locksmiths on tradedirectory.co.nz.
