Yes, fitting a sash jammer to an aluminium window frame is a DIY job most homeowners can tackle confidently. It requires only basic tools, no licensed trade work, and can meaningfully improve your home's security in under an hour. That said, aluminium frames need a slightly different approach than timber, so it pays to understand the process before you start.
What Is a Sash Jammer and Why Fit One?
A sash jammer (sometimes called a window lock or casement stay lock) is a simple lever-action device that prevents a sliding or casement window from being forced open from outside, even if the standard latch is defeated. They're a popular, low-cost security upgrade and are particularly useful for:
- Ground-floor windows
- Windows near doors or accessible from a roof or fence
- Rental properties needing to meet Healthy Homes Standards security requirements
- Any window where the existing latch feels inadequate
Tools and Materials You'll Need
- Sash jammer (choose one rated for aluminium frames — check the packaging)
- Cordless drill with a sharp HSS (high-speed steel) metal drill bit
- Self-tapping screws suitable for aluminium (usually supplied with the jammer)
- Centre punch or sharp nail
- Masking tape
- Pencil or marker
- Safety glasses
Sash jammers are widely available at Bunnings and Mitre 10. Look for a model that specifies compatibility with aluminium frames and comes with appropriate fixings.
Understanding Aluminium Frames Before You Drill
Aluminium window frames are hollow-section extrusions, which means the wall of the frame you're drilling into is relatively thin — typically 1.5–3 mm. This has a few practical implications:
- Use a sharp HSS drill bit sized to match your screws (usually 2.5–3.5 mm for self-tappers).
- Drill slowly and apply steady, moderate pressure — aluminium cuts easily and a sharp bit prevents the drill from skating across the surface.
- Do not overtighten screws. Aluminium strips easily. Tighten until snug, then stop.
- Because the section is hollow, standard wood screws won't grip well. Use the self-tapping screws supplied, or purpose-made aluminium frame fixings.
Step-by-Step Installation Guide
1. Choose the Right Location
Close the window fully. Position the sash jammer body on the fixed frame (the part that doesn't move), with the lever arm able to swing down and engage the sliding or opening sash. Mark the screw hole positions with a pencil.
2. Prepare the Surface
Stick a small piece of masking tape over each marked hole. This helps prevent the drill bit from skating when you start drilling. Use a centre punch or sharp nail to create a small indent in the tape at each mark.
3. Drill the Pilot Holes
Fit your HSS bit and drill at low-to-medium speed. Keep the drill perpendicular to the frame. Clear swarf (metal shavings) as you go — a quick burst of compressed air or a dry cloth works well. Remove the masking tape.
4. Fit the Jammer Body
Align the jammer over the holes and drive in the self-tapping screws by hand or with a screwdriver bit on low torque. Check the lever swings freely and engages the sash correctly.
5. Test Operation
Open and close the window several times. Engage and disengage the jammer. The lever should lock down firmly with no wobble, and release cleanly when lifted.
Choosing the Right Sash Jammer
| Feature | What to Look For |
|---|---|
| Frame compatibility | Explicitly rated for aluminium |
| Finish | Powder-coated or stainless to resist coastal corrosion |
| Screw type | Self-tapping, stainless steel preferred |
| Lever strength | Heavy-duty lever for ground-floor windows |
| Keyed option | Lockable jammers available for higher security |
For coastal NZ homes, a stainless steel or marine-grade finish will resist salt air corrosion far better than standard zinc-plated hardware.
NZ Building Code and Compliance Considerations
Fitting a sash jammer is not restricted building work and does not require a building consent under the NZ Building Code. It's a straightforward security accessory, not a structural alteration. However, keep in mind:
- Egress requirements: Building Code clause F6 requires that certain windows (particularly in sleeping rooms) can be opened from the inside without a key in an emergency. If you fit a keyed sash jammer on an egress window, ensure occupants can still escape quickly. A non-keyed jammer is generally safer for egress windows.
- Rental properties: Under the Healthy Homes Standards, landlords must ensure windows that can be opened have an appropriate latch. A sash jammer can complement — but check it doesn't interfere with — the required latch.
- If in doubt about compliance, check with your local council.
When to Call a Professional
While this is a genuine DIY job, consider calling a qualified locksmith if:
- You're unsure which type of jammer suits your specific window profile
- The frame is damaged, corroded, or the existing hardware is failing
- You want a keyed locking sash jammer installed correctly for maximum security
- You're fitting multiple windows and want a consistent, professionally finished result
- You're a landlord wanting documented evidence of security upgrades for Healthy Homes compliance
A professional locksmith can also assess your overall window and door security and recommend the best products for your situation. You can find qualified local locksmiths on tradedirectory.co.nz.
