Yes — fitting a door reinforcement kit is one of the most effective security upgrades you can make to your home, and in most cases it's a perfectly legal DIY job requiring only basic tools and a free afternoon. No building consent is typically needed for like-for-like hardware upgrades on an existing door, though it's always worth confirming with your local council if you're unsure about your specific situation.
Why Door Reinforcement Matters
Most forced entries in New Zealand don't involve picking locks — they involve kicking or shouldering a door until the frame or strike plate gives way. A standard strike plate is often held in place by short 25–30 mm screws that bite only into the door stop, not the structural framing behind it. A door reinforcement kit addresses this weak point by spreading the load across a much larger area of the frame and using long screws (typically 75–100 mm) that reach the wall framing or studs behind the lining.
What's in a Door Reinforcement Kit?
Kits vary, but most include some combination of:
- Reinforced strike plate — a heavy-gauge steel plate that replaces the standard strike plate
- Door edge guard / wrap-around reinforcer — a steel channel that wraps around the door edge where the lock bolt sits, preventing the door from being split
- Hinge reinforcers — steel plates that beef up the hinge side of the frame
- Long fixing screws — the most critical component; these must reach the structural framing
Some kits also include a door frame repair kit if the frame has already been damaged. You can find a range of options at Bunnings and Mitre 10.
Tools You'll Need
- Cordless drill and drill bits
- Screwdrivers (Phillips and flat-head)
- Tape measure and pencil
- Chisel and mallet (for mortising a recessed plate)
- Safety glasses
Step-by-Step: Fitting a Reinforced Strike Plate
1. Remove the existing strike plate
Unscrew the old plate and set it aside. Inspect the mortise (the recess in the frame) and the surrounding timber for any existing damage or rot.
2. Check your framing
Use a stud finder or probe gently with a thin nail to confirm where the structural framing sits behind the door lining. The long screws in your kit need to hit solid timber — typically the door jamb stud — to be effective.
3. Fit the new strike plate
If the new plate is larger than the old mortise, carefully chisel out the additional timber so the plate sits flush. A proud (raised) plate can prevent the door from closing properly.
4. Drive the long screws
This is the key step. Drive the supplied 75–100 mm screws at an angle if needed to ensure they bite into the structural framing behind the lining. Avoid over-tightening, which can split the timber.
5. Test the door
Close and latch the door several times to confirm smooth operation. The bolt should engage cleanly without binding.
6. Fit edge guards and hinge reinforcers
Follow the manufacturer's instructions for any additional components. Hinge-side reinforcers are fitted in the same way — remove the existing hinge screws one at a time and replace with the longer fixings.
Choosing the Right Kit for Your Door
| Door Type | Key Consideration |
|---|---|
| Timber framed | Most kits suit; check framing depth |
| Steel or aluminium door | May need specialist hardware; check with supplier |
| Hollow-core door | Frame reinforcement helps, but consider upgrading the door itself |
| French / double doors | Look for kits with flush bolts and astragal reinforcers |
If your door is a hollow-core interior door being used as an exterior door, reinforcing the frame alone won't be enough — the door leaf itself is the weak point and should be replaced with a solid-core or steel door.
NZ Building Code Considerations
Replacing hardware on an existing door is generally exempt from building consent under Schedule 1 of the Building Act 2004, as it is maintenance or like-for-like repair. However, if you're replacing the entire door or door frame, or making structural changes, you may need consent. Always check with your local council or visit MBIE Building Performance for guidance.
For rental properties, landlords should also be aware of **Healthy Homes Standards. Note that the Healthy Homes Standards primarily cover heating, insulation, ventilation, moisture, and draught stopping — check the Tenancy Services website for the current requirements applicable to your rental property. The Tenancy Services website has up-to-date information on what's required.
Safety Note
This work involves no electrical, gas, or plumbing components, so there are no restricted-work licensing requirements. Use safety glasses when drilling and chiselling, and take care when working near door edges to avoid pinch injuries.
When to Call a Professional
Consider engaging a qualified locksmith if:
- Your door frame is significantly damaged or rotten and needs structural repair
- You want to upgrade to a high-security deadlock or multi-point locking system at the same time (a locksmith can ensure correct installation and alignment)
- You're unsure whether your door or frame is suitable for reinforcement
- You're fitting security hardware to a commercial or rental property and want documented, professional installation
A licensed locksmith can also advise on whether your existing lock cylinder meets current security standards. You can find qualified local locksmiths on tradedirectory.co.nz.
