Making Windows More Secure From Thieves

The majority of break-ins, over 60% in fact, occur through windows, so you must take window security very seriously indeed. A wide variety of window locks have been produced to help you make your windows more secure. Most of these are effective and simple to fit. The type you choose depends on how your windows are designed.

Most at risk are small-paned windows because the glass- in these is usually fairly easy to break without making a great deal of noise which would attract attention. Once

Timber French doors

Being glazed and situated facing a garden where they may not be overlooked, these doors are always vulnerable and should be protected in several ways. Normally fitted with both doors opening outwards, the first closing door should be fastened with either flush bolts at top and bottom, recessed into the edge of the door and hidden by the second leaf, or with mortise rack bolts installed to shoot into the sill and head of the frame. The second closing door should lock to the first leaf with either a mortise deadlock or a hook-bolt mortise lock and also be secured at top and bottom with mortise rack bolts which shoot into the sill and head of the frame.

An alternative lock which can be fitted to French doors is an espagnolette bolt which extends the full length of the door and consists of two sliding bolts which by means of a central handle extend into recesses at the head and sill of the frame. Ideally, the handle should be lockable. If it is not then an additional mortise lock will be required.

Hinge bolts

A problem with doors which open outwards is that the hinges are exposed. It is possible that these can be tampered with, allowing the door to be opened on the hinge side. To prevent this from happening, hinge bolts should be fitted. These consist of a fixed bolt fitted into the edge of the door close to the hinge position and a matching the pane is broken the intruder can reach in to open the window and make his entrance.

With timber windows in particular, before fitting any type of lock, first make sure that the window frame is sound and that the putty holding the glass is in good condition. Secondly, do not take the easy way out and simply screw down opening windows so they cannot be opened. Even if the windows are not opened very often it is important to retain the option of opening them for ventilation when required. More important still, you should be able to open the window quickly in the event of a fire. In this respect some of the more expensive window security devices which operate by key are better than the cheaper devices which screw together and are therefore slower to unlock. The latter, if they are detachable, are also easily mislaid when they have been removed.

Casement-window locks

With casement (hinged) windows the best way to improve security is to change the fasteners for key-operated locking types. A cheaper alternative is to fit supplementary locking devices.

One of the best devices is the locking cocicspur handle which is fitted in place of the standard type. Alternatively, the cock-spur handle can be retained and security supplemented by key-operated casement-window locks. For maximum security you should fit two of these close to the top and bottom of each casement. These locks can also be used to secure top-hung fanlight windows. Another device is the automatic self-lock for hinged windows. This type locks automatically when the window is closed and is released with a key.

Mortise rack bolts

An excellent supplementary device for

securing hinged-windows closed is the mortise rack bolt which is fitted in exactly the same way as it is to doors. The bolt is slightly shorter than the door version. Surface-mounted dual screws work in a similar way, but they are not so neat in appearance.


A cheap and quick way to secure hinged windows is to fit casement stay-screws and stops. Although these are not as strong as the previously mentioned devices, they do have the advantage that they can hold a window in a partially open position.

Timber sash windows

Although horizontal sliding timber-framed windows are occasionally found, the vast majority are vertical sashes. Many of the locks for this latter type can be used an horizontal sliders, but if you are in doubt take the advice of your crime prevention officer.


The first stage in securing sliding sash windows is to fit a secure type of fastener. The old type of pivoting sash-fastener, which can be opened with a knife blade from outside, should be discarded and in its place either a cam-type fitch fastener or a screw-type Brighton fastener should be fitted. The action of closing these fasteners draws the sashes together which not only aids security but also considerably reduces draughts which can blow between the meeting bars.

Sash locks

In addition to improved fasteners you still need to fit security locks which cannot be undone simply by breaking the glass. However, there is an easy way out with windows you never open for ventilation and that is to screw the meeting rails together, although you must never screw all the windows in a room together in this manner because there must always be an escape route in the case of fire.

The quickest-acting sash window security device is the key-operated sash lock. Fit one of these on each side to the top edge of the lower (inner) sash. By operating the key the body of the lock can be slid forwards so that a bolt enters a hole in the outer (top) sash. By drilling two holes the top sash can be lowered a little for ventilation. Because this type of lock is key-operated it offers better security than the other devices mentioned below.


The first of these is the locking stop. In this case a metal plate is screwed to the outer sash, and into the plate a small stop can be screwed using a special key. At the top of the lower sash a protective metal plate is fitted and when the stop is in place the movement of the top sash is restricted. Although the stop cannot be removed by hand it is easy to remove it with a key of the right make. Again, two locking stops should be fitted per window.

Dual screws

A neater type of sash window lock is the dual screw which consists of a screwed bolt within an outer barrel. The barrel is fixed in a hole drilled in the rail of the lower sash and when the key is turned this screws in the bolt which engages in a hole drilled in

the meeting rail of the top sash preventing the window from being opened, but not allowing ventilation.

Metal casement windows

Many of the locks described under timber windows may also be used on metal ones but check on the pack before buying.

Steel windows

The majority of metal casement windows are made from steel or, more recently, galvanised steel. In the same manner as hinged timber windows, they are secured with cockspur handles and metal stays. There are a number of security locking devices for this type of window.

Cockspur-handle locks

Unlike those on timber windows, the sliding wedge lock

A problem with surface-fitting locks is that they are obtrusive and can be tampered with. An excellent securing device for metal casements is, therefore, the sliding-wedge lock, which is fitted inside the channel within the metal frame and is thus not only unobtrusive but also cannot be tampered with. The device should be fitted about 100mm below the window catch and requires only one hole to be drilled in the fixed part of the frame through which the lock is secured. When the key is turned in the lock the sliding wedge expands, preventing the window from being opened. The only snag with this lock is that it fits only medium section frames, so take careful measurements of the frame dimensions before purchasing.

Spur handle on steel windows is very difficult to change for a key-operated locking version, but there is a good alternative and that is to fit a cockspur-handle lock. There are various types of this lock which screw to the fixed frame below the handle fixing position and which have a sliding or pivoting bolt which can be locked into position with a special key to prevent the handle from being operated. As long as the handle has a secondary ventilation slot these devices will allow a degree of ventilation and it is fairly easy to release the bolt to allow the window to be fully opened.

However, where metal casement windows are rarely opened there are cheaper window-latch locks available which by means of a key provided, lock directly on to the cockspur handle to prevent it from being opened. The advantage of this type is that it can be fitted without needing to drill the window for screw fixing.

Key-operated casement-window locks Those key-operated locks which can be fitted to timber hinged windows can also be fitted to metal windows. In this case the lock is positioned on the opening frame so that there is maximum engagement of the bolt on the fixed frame. The frame has to be drilled carefully so that the window glass is not damaged and the lock is fixed using the self-tapping screws supplied.

Stay locks

There are also various devices for locking the window stay in position and this type is particularly useful with metal fanlights which are particularly vulnerable to break-ins. One screw-operated type of stay lock works like a clamp which very simply holds the stay on to its rest. Another type uses a key-operated locking screw through one of the holes in the stay to hold a bar under the stay retainer. There is also a type with a pivoting locking-bar, operated by

key, which is permanently attached to the window stay. The bar can be locked in place under the retainer to prevent the stay from being lifted.

Aluminium windows

Because the metal is so soft there is not a great deal that can be done to improve the security of aluminium replacement windows. Therefore, great reliance has to be placed on the locks originally fitted by the manufacturer. Some of the devices which are described for steel windows can be fitted to aluminium types, but in the latter case it is best to take the advice of your crime prevention officer. When buying new aluminium windows make sure that the security locks conform to BS4873 which will ensure as far as possible that the windows are secure.

Sliding windows

The best way to improve the security of horizontal or vertical sliding metal windows is to fit a key-operated lock, as recommended for patio doors, which screws on to the edge of the inside window and allows it to be locked to the outer pane.

If the window is not sufficiently wide to allow one of these locks to be fitted, fit instead a clamp-on type of lock which is attached to the sliding track to prevent the window from being opened.

Pivoting windows

Centre-pivot windows, both metal and timber types, can be secured with most of the devices intended for casement windows.

Louvre windows

By their nature these windows are very insecure. With the cheaper louvre mechanisms in particular, it is very easy to remove whole panes of glass from the metal clips. Make sure that the glass is well fitted in a good quality mechanism. It may pay to glue the glass in place with epoxy resin. Consider changing the window for a more secure type, or improve security by fixing an expanding metal-grille over the window.


If you have timber casement windows, the best protection is provided by mortise rack bolts, although key-operated cockspur handle locks are also good and are easier to fit. With timber sash windows, use the type of bolt that locks the two parts of the window together — these afford much better security than the basic catches found on most sash windows. Of the latter, Brighton fasteners give more protection than the simple fitch types. If you have metal casement windows, fit sliding wedge locks if possible — these are ideal because they are hidden and cannot be tampered with by an intruder. With metal sliding windows, try one of the screw-on or clamp-on locks. If you are having new windows fitted, pay particular attention to security, especially if .you have chosen aluminium double-glazed windows. It can be difficult to fit security devices to these.