Door Security

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Who do you need to protect against?

When thinking of security, people may take measures designed to counteract one group of attackers only. In reality all types of crime occur, and good door security can help reduce the risk of crimes by the following:

  • Casual burglars
  • More determined burglars
  • Vandals
  • Passing angry drunkards
  • Violent offenders
  • Distraction burglaries
  • Con artists
  • Arsonists (both recreational & resentful)
  • Resentful acquaintances

Information Sources

Police have crime prevention officers that can offer advice.

More precise advice is available direct from the home office online.

Neighbourhood watch schemes operate in some locations.

Government Recommendations

Most UK homes fall short of Home Ofice Recommendations on door security.

more recommendations

Stating the Obvious

It shouldnt be necessary to say some things, but the reality is 30% of burglaries are committed because people didn't lock their doors or didnt close the windows. A key left under something outside is another burglar's favourite. When burglary happens in these cases there is no real likelihood of a sucessful insurance claim.



The cylinder lock nightlatch, popularised by Yale, is useful to provide some security at times when people are home.

However these are low security devices not recommended for securing an unattended door.


Eurolock cylinders can be changed easily and quickly, without any need to dismantle a lock. This is a definite advantage from a security point of view, and it keeps lock change costs right down.

Eurolocks cover the range from weak security to fairly good.

Euros with no external security plate can be bent & broken, thus gaining entry.

Euros without hardened pins can be drilled

A good euro lock has a barrel with 6 hardened pins and an external security plate with no bolts accessible externally.

All cylinder locks share some vulnerability, so they're never the best possible option.


2 & 3 Lever

2 and 3 lever locks are cheap & quite easy to pick. These are generally adequate for interior locks where wanted, but offer weak security on external doors.

5 Lever

5 lever deadlocks to BS3621 are the recommended lock for external doors. They give good security, provided other suitable measures are also taken, and are reasonably priced, though not cheap.

Insurers may offer a discount if your external doors are secured by these, but this comes with a gotcha. If a burglary occurs when the 5 lever lock was not locked shut, your insurance is likely to be invalid. Thus there is thus an advantage to not saying you will secure the doors with 5 lever locks.

Higher Security Types

More secure locks are also available, and are recommended for situations where a thief is likely to have specific reason to spend some time targetting your property. These include 6 lever, 7 lever, and keying patterns that are harder to defeat.

Secure the Striker Plate

A fancy lock isn't worth much if a good kick can rip it off, or rip off the striker plate. Dont secure striker plates to the frame with short screws. Drill 3" in, and use long screws with wallplugs to fix it to the masonry. Choose the fattest and thus strongest steel screws that will fit.

Lock Positions

A single central lock is not recommended, as it allows a door to bend, permitting use of a jemmy. 2 locks at different height are recommended. As well as preventing jemmying, 2 locks also have the advantage of being significantly tougher to defeat than a single lock.


Additional bolts are recommended to minimise risk of forcing a door, and to prevent door bending, which enables jemmy attack.

1 bolt at each of top & bottom achieves this. These bolts are only fitted to one door, not both, as you can only put one set on before going out. Thus they are fitted to whichever door you dont use as the main exit & entrance route.

Tower bolts are a low cost option, but suffer from one defect when installed in the traditional way: any change in door alignment prevents them engaging home.

One way to avoid this problem that can be used on at least some doors is to attach the bolt to the wall or frame so that the bolt overlaps the door, and not fit the whatsitcalled-bottom-bit.

Other designs of bolt are available that avoid this defect, but price is higher.

Door Chain

The door chain is the only device that provides some degree of security when the door is open. This is particularly useful against wandering chancers, assault, and to a limited extent distraction burglaries. It also lets people know upfront that youre not a good crime target.

The security provided by a chain is not particularly high, but it is a fair bit better than nothing when the door is open.

Small door bars are also available as an alternative to chains. These are stronger but may permit less opening.


Seeing who is out there first can prevent a percentage of assaults & burglaries. A quick peek lets you know which you want to do:

  • open it fully
  • put the chain on
  • not answer the door
  • make sure you look perfect first
  • hide the bodies quick

Letterbox cage

  • Prevents reaching in to operate locks or reach nearby keys
  • Makes reaching in with wire more difficult
  • Prevents fishing out of letters for ID fraud from under the door
  • Check the cage shape prevents hand entry retrieving letters in the cage.

Restricting how far the letter flap opens is a free alternative to a cage when budget is short.



Plain glass in the door is vulnerable, especially when whole panels are glazed. Replacement with a security type of glass is best where the glass is without character. If not replaced, it can be reinforced with iron bars, not prison cell sized bars, but small discreet bars as used in leaded glazing.

Toughened, Laminated & Wired

Laminated & Wired glass both have extra resistance to attack, and do not normally need further protection.

Laminated glass is particularly good against forced entry because it requires repeated glass smashing attacks to get through it, and every hit makes the dreaded glass breaking noise.

Toughened glass is much stronger than plain & laminated glasses, but shatters completely in one go, so is not as secure as laminated.

Toughened is more expensive than lam, and glazing suppliers need time to get the glass hardened after it has been cut. Wired is the cheapest of the three, but doesnt look as good.


Leaded glass is weak, and must be reinforced by regular iron bars. Without this, entry is easy.

All Glass Doors

(need a better phrase for that)

Doors that consist only of an outer frame with full glass fill are not recommended. These are inherently insecure and are better replaced. If it is desired to keep the door, fitting laminated glass is the most secure option. However BR now requires toughened glass be fitted to such doors.

Post Box

Securing the letterbox permanently closed and fitting a post box is more secure than a letterbox cage.

  • Prevents wire access to locks thru the letterbox
  • Prevents arson
  • Prevents viewing of house contents
  • Is effectively a statement of security

Warning Signs

Some signs may give a quick indication that the householder is not careless about security, encouraging wandering thieves to look elsewhere.

Useful signs include:

  • Neighbourhood watch
  • Property security marked
  • Burglar alarm signs

Signs should be placed within view of anyone standing at the front door.

None of these signs prevent entry, and burglar alarm signs are not always effective deterrents, but signs do put some people off.

Hinge Bolts

Low on the external door security list is hinge bolts. These are concealed bolts on the hinge side that engage when the door is closed, thus reducing the chance of removing the door from the frame.

This is not one of the most popular methods of attack, but hinge bolts are very cheap and can stop the small number of more violent door attacks.

It may seem odd to secure a door against violent attack when a glass window is nearby, but attackers come in all types. Some dont want to climb in through a window, and some are in no state to think straight.

Key Loss

Never have anything that can identify you or your house on your keyring.

If you lose a key, replacing the lock or lock barrel is a good idea.

Some insurance companies operate key return schemes. You put their tag on your key with a code, and if its handed in to them they pay the finder £10 and return the keys to you.



Cylinder locks are only rekeyed by fitting a new lock barrel. Rekeying by swapping pins is impractical.


5 Lever locks can be rekeyed once by swapping lever positions and purchasing new keys to fit from a key cutter. The lever pattern must always be symmetrical. This rekeying method is useful for higher priced locks, where it avoids:

  • the cost of a new lock
  • the cost of fitting the new lock

Cutting keys with no master key takes longer, so visiting the key cutter during a quiet time is a good plan, otherwise your request may be refused.

New House

Always rekey all external locks when you buy a house. You have no idea who has keys to those doors.

Used Locks & Barrels

Used Locks & Barrels are fine if the seller has no way to know where you live. But if you let them have your address you have effectively given them the key to your door.

Heavy Duty Security

Where repeat attacks have occured, or heavy physical attack is expected, there are further measures that can improve security.

Steel Plate

Steel doors are justified where heavy physical attack is expected, or where burglars may work on a door undisturbed.

Steel doors and frames are available, but not cheap. A lower cost DIY option is to face plywood with a sheet of 1.6mm mild steel.

Extra attack resistance is imparted if the steel is folded at 90 degrees over the wood around the 4 edges. If only one edge is folded, it should be the bottom edge, which is otherwise the weakest point.



For locations where crime is expected, monitored CCTV is an effective option.


Unmonitored CCTV is sometimes effective, but it should be a system with sufficient video quality and suitable recording format for evidence, and the recording equipment needs to remain undetected by the intruder, or they will simply take the tape.


Basic low cost systems may put off some, but will not stop someone that knows what theyre doing and comes back prepared. Generally they aren't much use as evidence.


Patrols make a real difference to business premises security. The same principle can be applied to homes by letting someone trustworthy stay in your house when you go away, eg on holiday.

Insurance companies need to be notified if the house willl be unoccupied for 30 days or more, as the risk increases significantly.

See Also


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