Replacing a window lock on an aluminium joinery frame is a job many NZ homeowners can tackle themselves, provided you can source a matching replacement lock. The trickiest part is usually identifying the correct part — aluminium joinery comes in many proprietary systems, so getting the right fit matters. Here's how to go about it safely and correctly.
Understand Your Joinery System First
NZ homes use a wide variety of aluminium window systems — brands like Altherm, Metro, Vantage, and Rylock are common, and each uses its own hardware. Before you buy anything, identify your joinery brand if possible. Check for a label or stamp on the frame, often found on the inside edge of the sash or frame. If you can't find a brand, take the old lock with you to a hardware store or locksmith for matching.
Window locks on aluminium joinery generally fall into a few types:
- Sash locks (also called cockspur handles) — the most common on sliding and casement windows
- Cam locks — a rotating barrel lock, often on awning windows
- Inline sliding locks — used on sliding windows and doors
- Key-lockable stays — used on awning or casement windows for security and ventilation
Tools and Materials You'll Need
- Flathead and Phillips head screwdrivers
- A small drill and appropriate drill bits (if re-drilling screw holes)
- Replacement window lock (matched to your joinery)
- Pencil for marking
- Masking tape (optional, to protect the frame finish)
Replacement locks are available from Mitre 10 (https://www.mitre10.co.nz), Bunnings (https://www.bunnings.co.nz), and PlaceMakers (https://www.placemakers.co.nz), or directly from a locksmith or joinery supplier. As a rough guide, basic replacement sash locks can cost anywhere from around $10 to $50+, depending on type and brand — but prices vary, so check with your supplier.
Step-by-Step: Replacing the Lock
1. Remove the Old Lock
Open the window fully so you have clear access. Use a screwdriver to remove the screws holding the lock body to the frame. Keep the screws — you may be able to reuse them if the new lock has the same hole spacing. Gently wiggle the lock free; some locks have a small clip or tab holding them in place.
2. Inspect the Frame
Check the screw holes and the surrounding aluminium for damage or corrosion. Aluminium doesn't rust, but it can corrode in coastal environments. If the screw holes are stripped, you can use slightly larger screws or fill the holes with a suitable epoxy before re-drilling.
3. Match the Replacement Part
Compare the old lock to your new one carefully:
- Screw hole spacing (centre-to-centre distance)
- Backset (distance from the edge of the frame to the lock body)
- Hand (left or right — some locks are handed)
- Finish (anodised silver, white, or black to match your joinery)
If you're unsure, a qualified locksmith can identify and source the correct part for you.
4. Fit the New Lock
Position the new lock body on the frame, aligning it with the existing screw holes. If the holes don't align, mark the new positions with a pencil. Use masking tape over the frame to protect the finish while drilling. Drill pilot holes carefully — aluminium is soft and easy to over-drill. Secure the lock with the supplied screws, being careful not to overtighten and strip the threads.
5. Check the Keeper/Strike Plate
The keeper (or strike plate) is the part on the fixed frame that the lock engages with. Check that the new lock aligns and engages smoothly with the existing keeper. If it doesn't line up, you may need to adjust or replace the keeper as well — this usually involves the same removal and re-fixing process.
6. Test the Lock
Open and close the window several times, engaging the lock each time. It should operate smoothly without excessive force. A stiff or misaligned lock won't provide reliable security.
Security and Healthy Homes Considerations
Window locks play an important role in home security and, for rental properties, in meeting Healthy Homes Standards. Under the Healthy Homes regulations, rental properties must have windows that can be secured — so a broken or missing lock may put a landlord in breach of their obligations. Check the requirements at Tenancy Services.
For ground-floor windows or those accessible from outside, consider upgrading to a key-lockable replacement lock for added security. BRANZ provides useful guidance on home security and weathertightness that's worth reading.
Does This Require a Building Consent?
Replacing a like-for-like window lock is routine maintenance and does not require a building consent under Schedule 1 of the Building Act. However, if you're modifying the window itself — for example, changing the type of opening or adding a new lock mechanism that alters the joinery — check with your local council first. Visit MBIE Building Performance for guidance on what work is exempt.
When to Call a Professional
Call a qualified locksmith or joinery specialist if:
- You cannot identify the joinery brand or source a matching part
- The frame itself is damaged, bent, or corroded
- The window no longer closes or seals properly
- You need key-alike locks across multiple windows (a locksmith can key them to match)
- You're a landlord needing to meet Healthy Homes compliance quickly
A licensed locksmith can source proprietary parts, rekey locks, and ensure everything is fitted correctly. You can find trusted local locksmiths on tradedirectory.co.nz.
