How to Fix a Door That Won't Lock Because It's Misaligned

A door that won't lock properly is more than an annoyance — it's a security and safety issue. In most cases the culprit is a misaligned latch or deadbolt that no longer lines up with the strike plate on the door frame. The good news is that many alignment problems are straightforward DIY fixes requiring only basic tools and a bit of patience.

Why Doors Go Out of Alignment

Before reaching for your screwdriver, it helps to understand what's causing the problem. Common reasons include:

• Settling or movement — NZ homes, especially older timber-framed houses, shift over time as the ground moves or timber dries out and shrinks.
• Seasonal swelling — Timber doors absorb moisture in humid or wet conditions (common in many NZ regions), causing them to swell and bind.
• Loose or worn hinges — Hinge screws work loose over years of use, letting the door sag.
• Foundation movement — More significant structural movement can rack a door frame out of square.
• Poor original installation — Sometimes the door was never quite right from the start.

Step 1 — Diagnose the Problem

Close the door slowly and watch where the latch or bolt meets the strike plate. Ask yourself:

• Does the latch hit above or below the strike plate opening?
• Does it hit to the left or right?
• Does the door feel tight or binding in the frame?
• Is there a gap between the door edge and the frame on the hinge side?

A quick trick: rub a lipstick or crayon on the end of the latch bolt, then close the door. The mark left on the strike plate shows exactly where the bolt is landing.

Step 2 — Tighten the Hinges

Loose hinges are the most common cause of a sagging door. Start here before doing anything else.

1. Open the door and check every hinge screw. Tighten any that are loose.
2. If screws spin without gripping, the timber holes are stripped. Remove the screw, push a wooden toothpick or matchstick dipped in PVA glue into the hole, snap it off flush, let it dry, then re-drive the screw.
3. For a more permanent fix, replace short screws (often only 25–30 mm) with longer 65–75 mm screws that reach into the structural framing behind the lining.

After tightening, test the door again. Many alignment issues disappear at this step.

Step 3 — Adjust or Reposition the Strike Plate

If the latch is only slightly off — say, less than 3–4 mm — you can often fix it by adjusting the strike plate rather than moving the door.

Filing the Strike Plate

Use a metal file to enlarge the strike plate opening in the direction the latch needs to travel. This is a quick fix for minor misalignment.

Repositioning the Strike Plate

1. Remove the strike plate screws.
2. Mark the new position with a pencil.
3. Use a sharp chisel to extend the mortise (the recess in the frame) in the required direction.
4. Refit the strike plate and fill any exposed gap with wood filler, sand, and paint to match.

Step 4 — Plane or Sand a Swollen Door

If the door is binding because of moisture swelling, you may need to remove a small amount of timber from the door edge.

1. Identify where the door is binding (look for shiny or worn patches on the edge).
2. Remove the door from its hinges.
3. Use a hand plane or belt sander to carefully remove a small amount of timber — take off a little at a time and keep testing the fit.
4. Once the door moves freely, seal the bare timber edge with primer and paint to prevent future moisture absorption. Leaving it unsealed will just cause the problem to return.

Step 5 — Adjust Hinge Positions

If the door needs to move more than a few millimetres, you may need to reposition a hinge.

• Packing a hinge (placing thin cardboard or a hinge shim behind it) pushes the door away from that side of the frame.
• Deepening the hinge mortise with a chisel pulls the door closer to the frame on that side.

This takes a bit of trial and error, so adjust one hinge at a time.

When to Call a Professional

Some situations are best left to a qualified locksmith or carpenter. Call a professional if:

• The door frame or surrounding structure appears racked, cracked, or significantly out of square — this could indicate foundation or structural movement that needs assessment.
• You have a multi-point locking system (common on modern exterior doors and ranch sliders) where the mechanism itself may need adjustment or replacement.
• The lock cylinder or deadbolt mechanism is damaged or faulty — a licensed locksmith should handle lock repairs and replacements to maintain security integrity.
• You've tried the steps above and the problem keeps returning.
• The door is part of a fire-rated or smoke-stop assembly — these must be maintained to their rated specification.

For significant structural movement, it's worth checking whether any work requires a building consent. Most minor door repairs fall under Schedule 1 exemptions, but always confirm with your local council if you're unsure. The MBIE Building Performance website has useful guidance on what work requires consent.

You can find a qualified local locksmith or carpenter on tradedirectory.co.nz.

A Note on Security

A door that doesn't lock properly is a real security risk. If you can't fix the problem quickly, use a door chain or temporary security bar in the meantime, and prioritise getting it sorted — especially for exterior doors.

Sources & Further Reading

• MBIE Building Performance — Building Consent Exemptions
• BRANZ — Maintenance and Repair Guidance
• WorkSafe NZ — Safe Use of Hand Tools
• Bunnings — Door Hardware and Tools
• Mitre 10 — Door and Lock Hardware