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How to Change Locks on uPVC Doors

A uPVC (unplasticised polyvinyl chloride) door is an increasingly common choice in many homes due to its sturdy and insulating properties. There may be circumstances when you need to change the locks on your uPVC door. Perhaps you’ve lost a key, experienced a break-in, moved to a new home, or simply wish to upgrade your lock for added security.

Whatever the reason may be, changing locks on a uPVC door is a critical task that demands a high degree of precision and attention to detail. While it is possible to perform this task yourself, the process can be quite complex, and even a small mistake can compromise the security of your home. This guide will walk you through the steps of changing locks on a uPVC door.

Step 1: Purchase the Right Replacement Lock

Before starting any work, the first and most critical step is to purchase the appropriate replacement lock. uPVC doors are usually equipped with euro cylinder locks, a design that offers both security and ease of use. However, these locks come in varying sizes, necessitating accurate measurement of your existing lock to ensure an exact fit.

Start by locating the securing screw on the side of your door; it holds the lock firmly in place. Using a suitable screwdriver, remove this screw carefully. With the screw removed, the lock should be free to slide out, revealing the cylinder for you to measure.

To measure the lock cylinder, you’ll need to take note of the distances from the center of the fixing hole to each end of the cylinder. Precise measurement is paramount here as these values will directly determine the size of your replacement lock. Remember to use a reliable measuring tool for the most accurate results.

British standard Euro Cylinder lock

Once you’ve obtained the measurements, it’s time to source your replacement lock. Opt for a high-quality, anti-snap cylinder lock that has been rated for security. While these locks might be slightly more expensive, they provide an enhanced level of protection for your uPVC door, deterring potential break-ins and improving overall security. Your choice of lock should always prioritise safety, and an investment in a top-grade cylinder lock will provide peace of mind and effective security in the long run.

Step 2: Insert the New Lock

Once you have removed the old lock and sourced a new one, it’s time to insert the new one. This process may seem straightforward, but careful attention to detail is vital for ensuring successful installation and subsequent operation. Start by inserting your key into the new lock, then gently rotate it in the same direction you did when extracting the old lock. This alignment is important to help guide the lock into its proper position.

As you gently introduce the new lock into the door, concentrate on aligning it perfectly with the fixing hole. The new lock should slide in smoothly, with no force necessary. Misalignment here can cause difficulties in future operations, and in the worst cases, a poorly fitted lock can compromise the security of your door.

It’s also crucial to test the key insertion and removal process at this point. The key should glide smoothly into the lock, and you should be able to remove it without any resistance. This test can help you identify potential issues early and make necessary adjustments.

Once you are confident that the new lock is correctly positioned and operating smoothly, it’s time to secure it in place with the fixing screw. When inserting the screw, make sure it fits comfortably without the need for excessive force. A common mistake to avoid is overtightening the screw; while it may seem to provide extra security, it can lead to mechanical issues with the lock’s operation, impairing its effectiveness.

Step 3: Test the New Lock

Before you close the door, it’s important to conduct a comprehensive test of the new lock. Insert the key and rotate it in both directions, observing how the latch responds. This operation should be smooth, with no resistance or unusual sounds. Furthermore, make sure the latch fully engages and disengages as it should.

It’s also a wise practice to test the door’s operation from both the inside and the outside. This dual perspective will give you a complete understanding of the lock’s functionality and identify any potential issues that might compromise security, such as the lock working when open, but not when closed.

A Word of Caution

Although this guide provides a general overview of how to change locks on a uPVC door, remember that every door and lock can have unique features that may complicate the process. This task demands precision, and even the slightest misalignment can lead to serious security risks.

Given the complexity and high stakes of this job, it’s often advisable to hire a professional locksmith, particularly if you’re not a seasoned DIY enthusiast. Not only do locksmiths have the right tools and expertise, but they also ensure that your new lock is fitted correctly and securely. Your peace of mind and the security of your home are well worth the investment.

While it’s possible to change the locks on your uPVC door yourself, it’s a task that should be approached with caution. Whether you choose the DIY route or decide to hire a professional, remember that the aim is to enhance your home security effectively and reliably.

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Murray - Veteran Locksmiths


Murray is a seasoned locksmith with a wealth of expertise in the field. As the founder of Veteran Locksmiths, he combines his extensive knowledge of locks and security, with years of experience servicing the South Coast delivering excellent locksmithing solutions. Murray's dedication and commitment to exceptional service has earned him a reputation as a trusted and reliable expert in the industry.

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Veteran Locksmiths

Local mobile locksmith offering emergency, commercial and domestic locksmith services. Covering the whole of Hampshire, West Sussex and Surrey.


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