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How To Fix A Window Lock In 10 Steps

windows with locked

It is scary when a lock breaks on a window because intruders can easily use it to enter your home, whether you are there or not. Nobody wants that, so we’re here to help you fix your window lock ASAP. When a window lock is worn, damaged, or loose, it’s best to replace it entirely.

Not doing so will increase your risk of not just break-ins but also humidity, which can lead to mold. Properly sealed windows are vital to keeping your home well-ventilated. Home repairs can seem daunting, but they’re not difficult if you have the tools and follow our handy step-by-step guide.

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First of all, this guide assumes that your lock broke while the window is in the open position. If your window lock has been broken in a way that’s jammed the window shut, skip to the section below on fixing jammed windows.

Before we start, you’ll need to measure your window lock to ensure you get a compatible replacement lock.

4 Steps To Measure Your Window Lock:

Step One

Measure from the outer edge of the lock to the center of the handle to get your backset size. Standard backset sizes are 20 mm (millimeters) and 22 mm.

Step Two

Measure from one end of the window lock faceplate to the other side to get the length. Common sizes include 400 mm, 600 mm, and 1,000 mm.

Step Three

Alternatively, look on the lock faceplate for a manufacturer name and code. Letters in the code vary, but the numbers are typically the size of the lock.

Step Four

Finally, measure the width of the lock. The most common size is 16 mm, but you will want one slightly wider if you have a metal or vinyl window frame.

You Will Need:
  • Replacement lock with same dimensions as the broken lock
  • Drill with bits
  • Screwdriver (optional)
  • Wood putty
  • Fine-grit sandpaper (120+)
  • New screws (only if the old ones are stripped or worn)

How To Fix A Window Lock | Step-By-Step Guide

Step by step:
  • Step One: Remove the screws securing the window lock handle using your screwdriver or drill.
  • Step Two: Remove the window handle.
  • Step Three: Unscrew and remove the screws securing the lock on the faceplate.
  • Step Four: Remove the window lock.
  • Step Five: This step is for wooden windows only. For aluminum or vinyl frames, skip this step. Fill the mounting holes with wood putty and wait for it to dry. Sand the putty until it is flush with the window frame.
  • Step Six: Insert your replacement window lock where you removed the old one.
  • Step Seven: Insert your window handle and ensure it’s in the correct position.
  • Step Eight: Reinsert the screws securing the window handle. You can pre-drill holes for a metal frame to make the process easier.
  • Step Nine: Insert the screws securing the faceplate of the window lock. It may be necessary to drill holes in some cases.
  • Step Ten: If the lock is not the same type as the old, broken lock, it may be slightly different in dimensions. You may need to fiddle with it to get it in position with the window frame.
fixing window lock
Photo Credit By: monte_a, Shutterstock

What If The Window Lock Is Jammed?

If your window lock is broken in a way that has jammed your window shut, the process is much more laborious because you’ll have to replace the window seals. Doing so will void any warranties on the window, and you’ll risk damaging it. We recommend hiring a professional to do this if you’re not confident in your DIY skills.

If you’d rather do it yourself, we understand. You’ll need a few tools for the task.

You Will Need:
  • Drill with bit
  • Vice grips/channel locks
  • Allen keys
  • Screwdriver
  • Hammer (if the mechanism is rusted shut)
fixing shut window with broken lock
Photo Credit By: Maryana Serdynska, Shutterstock

How To Open A Shut Window With A Broken Lock

Step by step:
  • Step One: Unscrew the screws securing the window handle, and check the lock to ensure the handle isn’t broken. Sometimes, it seems like the lock is broken when it’s just the handle.
  • Step Two: Completely remove the handle.
  • Step Three: Use a screwdriver to carefully pry out the window seal between the window and the frame. Once it comes loose, you can pull it with your hands.
  • Step Four: Clamp the vice grips onto the long, straight end of your Allen key.
  • Steep Five: Holding it horizontally, insert the Allen key into the gap where the seal was.
  • Steep Six: Slide it down the gap until it hits the lock.
  • Steep Seven: With the tip of the Allen key in the lock, sharply turn the vice grips to disengage the locking mechanism. If the lock is rusted or seized, you may need to tap the vice grips with a hammer to get it to loosen.


Repairing a window lock secures your home from intruders, prevents air from escaping, and keeps your utility bills reasonable. In most cases, you can repair your window lock without paying a professional, but you must ensure your window’s manufacturer does not limit the types of repairs. Some window makers only honor warranties when their technicians repair their products.

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Featured Image Credit: Emily Wang, Unsplash


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