When moving into a new house, changing the door locks is an excellent way of ensuring the property is secure. If all other repair methods have failed, it might be time to replace an old door lock.
Find a replacement lock in our doors and windows range. Here, you'll find a selection of door handles and door knobs as a perfect way to give your door a quick upgrade. If your door has seen better days, it might be time for a full change - find a replacement that complements your home in our internal doors and external doors ranges. You can also learn how to hang an internal door in our handy guide.
In this guide, we’ll show you how to change three common types of locks:
We’ll also show you how to fit security door bolts into a wooden door for extra security. Plus, we’ll discuss the preparation needed before getting started and tips on staying safe.
What are the different types of locks?
This guide will cover the three types of door locks. Here’s a summary of each lock’s main characteristics:
Mortice sash locks: Also known as bolt through latches, these locks are commonly found on internal doors; mortice sash locks are pretty large and so a mortice, or hole, needs to be created so they can slot into the door edge
Euro profile cylinder locks: Commonly used on exterior doors, Euro profile cylinder locks offer more security than mortice sash locks; this type is also easier to replace, as the whole mechanism doesn’t need to be removed
Rim cylinder lock: This lock is ideal if you have a thin door and can’t drill a mortice hole. Rim cylinder locks are attached to the door’s surface and are commonly found on external doors
Preparing to fit and replace a door lock
When choosing replacement locks, it’s best to go for BS3621 or Kitemarked products. In many cases, your insurer will insist on this. If you’re replacing a lock on a final exit door, especially external doors, choose one with at least five levers certified to BS3621.
Remember that different lock designs may have additional fitting requirements, so always check the manufacturer’s instructions.
Preparing to fit a mortice sash lock
When replacing a mortice sash lock, select one that’s compatible with your old lock
If the distance from the edge of the door to the centre of the keyhole is 45mm, you need a 64mm lock; if it’s 57mm, you’ll need a 76mm lock
Your new lock must have the same distance between the centre of the keyhole and spindle as the old lock; installation will be more straightforward if it also has the same or similar-sized faceplate and strike plate
Preparing to fit a Euro profile cylinder lock
These locks all have the same profile, so finding and fitting a replacement is more straightforward; however, you need to choose one that’s the same size as the one you’re replacing.
Measure from the centre of the fixing screw to the outside of the lock on both sides. Deduct five from each measurement and put a 10 in the middle; for example, if the lengths are 45mm and 50mm, you need a 40:10:45 product
If the Euro profile cylinder lock you’re replacing sticks out more than 5mm beyond the door handle faceplate, it’s vulnerable to a ‘snap attack’; choose a replacement that protrudes less
Most Euro profile locks have a keyhole on both ends, but some have a keyhole outside, and a thumb turn inside; these tend to be less secure
Preparing to fit a rim cylinder lock
Ensure your new lock is a British standard rim cylinder, as it will have been independently tested to ensure it can withstand all known forms of attack
Preparing to change a door lock
Mark the position of your fixing points to ensure accuracy
Only use screws and fixings that are provided or recommended by the manufacturer
If your door has glass panels, improve security by fitting toughened glass and a key-operated deadlock so the handle can’t be turned if the glass is smashed
How to change a door lock safely
Here are some tips on keeping safe when changing door locks:
Doors can be heavy, so it’s best to ask for help when taking a door off its hinges or rehanging one
How to change a mortice sash lock:
step by step
Remove the faceplate, handle and spindle
With the door open, turn the key so the bolt is locked. Take out the key, then remove the screws holding the faceplate, internal door handle and spindle bar.
Make sure to keep the handle and spindle for later.
Remove the old lock
Using a pair of pliers, grip the bolt and pull out the old lock.
Adjust the mortice
Compare the size and shape of the two lock bodies and faceplates. If the new ones are larger, use a hammer and chisel to enlarge the mortice. Continue to adjust the mortice until the new lock fits.
Fit the faceplate
Once the lock body is in place, screw the faceplate into position. Then, replace the spindle bar and handle. Check that the new key turns smoothly in the lock.
Position the new strike plate
Remove the existing strike plate from the door frame, then hold the new one in position to see if it fits. If needed, mark any required adjustments on the recess before using a hammer and chisel to remove the excess wood.
Fit the strike plate
Secure the strike plate in position with the supplied screws. Finally, close the door and check the bolt engages with the strike plate.
How to change a mortice sash lock:
step by step
Remove the faceplate, handle and spindle
With the door open, turn the key so the bolt is locked. Take out the key, then remove the screws holding the faceplate, internal door handle and spindle bar.
Make sure to keep the handle and spindle for later.
Remove the old lock
Using a pair of pliers, grip the bolt and pull out the old lock.
Adjust the mortice
Compare the size and shape of the two lock bodies and faceplates. If the new ones are larger, use a hammer and chisel to enlarge the mortice. Continue to adjust the mortice until the new lock fits.
Fit the faceplate
Once the lock body is in place, screw the faceplate into position. Then, replace the spindle bar and handle. Check that the new key turns smoothly in the lock.
Position the new strike plate
Remove the existing strike plate from the door frame, then hold the new one in position to see if it fits. If needed, mark any required adjustments on the recess before using a hammer and chisel to remove the excess wood.
Fit the strike plate
Secure the strike plate in position with the supplied screws. Finally, close the door and check the bolt engages with the strike plate.
How to change a Euro profile cylinder lock:
step by step
The cylinder lock can be removed without taking out the entire mechanism, so replacing a Euro profile cylinder is more straightforward than a mortice sash lock.
Prepare the door
Open the door and remove the central lock fixing screw. Slightly loosen the door handles to help ease the removal of the cylinder.
Slide out the lock
Place the key in the lock and gently pull it towards you as you turn it to the left (10 o’clock) or right (2 o’clock) positions to align the cam. When the cam is aligned, the lock should slide out towards you.
Fit the new cylinder
Insert the new cylinder into the lock and replace the fixing screw. Then, tighten the handles. Use the key to test the new lock on both sides before closing the door.
How to change a rim cylinder lock:
step by step
Unscrew lock body and rim cylinder
On the inside of the door, unscrew the existing lock body. Keep this to one side, as it will be refitted later. Then, unscrew the two screws holding the existing rim cylinder lock.
Remove the old lock
Push out and remove the old lock, making sure not to move the mounting plate on the inside of the door.
Adjust the new lock
If the overall length of your replacement lock is longer than the old one, use a hacksaw to shorten the tail bar so the two locks are the same length.
Insert the new lock
Push the new cylinder into place and fix it with the two screws provided.
Refit the lock body
Screw the lock body back into position and use the new key to test that it works before closing the door.
Fit a pair of security door bolts:
step by step
If you require some additional security to an internal door or external door, adding a pair of security door bolts will do just that. Here’s how to install security door bolts:
Measure the bolt depth
Select a wood drill bit of the size recommended in the manufacturer’s instructions. Mark the bolt’s depth on the drill bit with masking tape.
Drill bolt holes
Drill a pair of horizontal holes to the marked depth into the centre point of the door’s edge. The holes should be near the top and bottom of the door.
Carve endplate positions
Slide the door bolts into position and mark the outline of the endplates onto the edge of the door. Use a hammer and chisel to remove wood from within the markings so the endplates sit flush with the door.
Measure keyhole positions
Hold the bolts against the inside of the door, flush with the edge. Use a carpenter’s awl to mark the position of the keyholes.
Drill the keyholes
Using a wood drill bit of the recommended size, drill the keyholes. Be careful not to drill through the door and only on the inside.
Place the door bolts into position, then put the keys through the new keyholes to check they line up and turn smoothly.
Drill endplate and keyhole screws
Use a pencil to mark the endplate and keyhole plate screw positions, then use a small wood drill bit to create pilot holes. Screw the endplates and keyhole plates and double-check that the key and bolt still turn smoothly.
Fit the strike plates
Follow the bolt manufacturer’s instructions and the above process to drill and fit the strike plates. Most door bolts have a small bump on the end that can mark the bolt’s position onto the frame to ensure accuracy. Check this when the door is shut, and the key is turned.
Lock installation aftercare
Ensure your locks are clean and lubricated to keep them in good working condition. Use suitable lubricants for the material and finish; using the wrong product could cause permanent damage.
