7 Questions to Ask Before Replacing Your Deadbolt Lock

Replacing a Deadbolt? Think Before You Buy

A deadbolt is one of the most important security investments you can make for your home. Done well, a replacement gives you years of reliable protection. Done poorly - wrong type, wrong size, poor installation - and you may end up with a false sense of security.

These seven questions will help you make the right decision.

1. Why Do I Actually Need to Replace My Deadbolt?

Before spending any money, be clear about your reason for replacing the lock. Different reasons call for different solutions:

Wear and tear (stiff key, loose cylinder, visible damage) - a direct replacement of the same type usually suffices
Lost or stolen keys - full replacement is the safest option; rekeying may be sufficient if the lock is in good condition
After a break-in - replace with a higher-security model and review the door frame too
Moving into a new property - always replace locks, as you have no way of knowing how many copies of the old keys exist
Security upgrade - newer deadbolts offer significantly better protection against picking, drilling, and bumping

If your existing lock is still in good condition and you have simply lost a key, rekeying is often a faster and more cost-effective option than full replacement.

2. Which Type of Deadbolt Is Right for My Door?

Single Cylinder Deadbolt

The most common type. Operated by key from the outside and a thumb-turn from inside. Suitable for most residential exterior doors. The one vulnerability: a door with glass panels near the lock could allow an intruder to break the glass and use the thumb-turn.

Double Cylinder Deadbolt

Requires a key on both sides. Eliminates the thumb-turn vulnerability on glass-panel doors, but introduces a safety concern - in a fire or emergency, occupants need a key to exit. If you choose this type, always keep a key accessible near the door and ensure all household members know where it is.

Electronic / Smart Deadbolt

Replaces the key and thumb-turn with a keypad, app, or other electronic method. Ideal if you want keyless access, remote control, or access logs. See our guide to smart locks for more detail.

3. Does the New Lock Fit My Door?

Two measurements are critical:

Backset: The distance from the edge of the door to the centre of the lock hole. UK residential doors typically have a backset of 44mm or 57mm (roughly 2⅜” or 2¾”). Measure this before purchasing a replacement.

Bolt length: The standard residential deadbolt throw is 25mm (1 inch). For improved security, a longer throw (32mm or more) provides greater resistance to door kick-ins.

If you are replacing like-for-like, the existing hole and strike plate recess should accommodate the new lock. If you are switching types (for example, from a basic deadbolt to a mortice deadlock), modifications to the door and frame will be needed - best left to a professional.

4. What Is the Security Rating of the Lock?

In the UK, look for locks certified to British Standard BS 3621. This certification means the lock has passed independent testing for resistance to picking, drilling, and forced entry, and is recognised by most home insurers.

Also look for:

Sold Secure or Secured by Design certification - additional endorsements used by police-preferred products
Anti-snap cylinders - essential for Euro cylinder locks on uPVC and composite doors, where snapping attacks are common
Anti-pick and anti-drill pins - standard on quality locks; check the product specification

5. How Will It Be Installed?

Proper installation is just as important as the quality of the lock itself. A poorly fitted deadbolt - loose in the door, with misaligned strike plate, or with inadequate screws - can be defeated even if the lock itself is excellent.

DIY installation is feasible if you are replacing a deadbolt with an identical fitting and have basic woodworking skills. The manufacturer’s instructions must be followed precisely.

Professional installation is strongly recommended if:

You are changing to a different lock type that requires new holes or a rebated mortice pocket
Your door frame needs reinforcement
You are fitting a smart lock with wiring requirements
You want the work guaranteed

A professional lock change typically takes 30-60 minutes and comes with the assurance that the fitting is correct.

6. What Is My Budget - and Am I Spending It Wisely?

Entry-level deadbolts start at around £20, but a certified BS 3621 lock with anti-snap protection typically costs £40-£80 for the cylinder and lock body. Smart deadbolts range from £100 to £250+.

Spending more on a quality lock is a sound investment - but do not neglect the frame. The strongest lock in the world will not stop a determined intruder if the door frame can be kicked apart. Pair a quality lock with:

A solid hardwood or composite door
A reinforced strike plate secured with 75mm screws into the structural frame (not just the door casing)
Hinge bolts on the hinge side of the door

Check our locksmith price list for professional fitting costs alongside the price of the lock.

7. How Will I Maintain the New Lock?

A quality deadbolt should last many years with minimal maintenance:

Clean the exterior face with a damp cloth; avoid bleach or abrasive cleaners
Lubricate the keyway and bolt mechanism every six months using graphite powder or a silicone-based lubricant - avoid oil-based products, which attract dirt
Inspect annually for loose screws, cylinder movement, or any misalignment with the strike plate
Replace promptly if you notice stiffness, difficulty turning, or visible wear - a lock that is hard to operate is already compromised

Ready to Replace Your Deadbolt?

City Locksmith London supplies and fits a wide range of high-security deadbolts and Euro cylinder locks across London. Whether you need a straightforward like-for-like replacement or a full security upgrade, we can advise on the best option for your door and budget.