Window Security

sash jammer

U-PVC Windows

Illustration of UPVC lock mechanismIn many cases it is not possible to retro-fit any extra locks to UPVC windows. This is because the material used is not strong enough to support a metal lock fitted with steel screws. It could also damage the window and perhaps invalidate any existing warranty.

Double glazed window locking systems should be fitted at the time of manufacture. A general rule to follow is that the handle should not be the only means of keeping the window closed. The locking system should be fitted within the framework and the handle is used as a means of throwing or engaging the internal locking system.

Always consult the manufacturer/supplier before attempting to fit any extra locks. There are locks that can be fitted to UPVC casement windows, but only if there is no integral locking system within the framework, typically where the only means of security is a locking handle.

There are two main types of locking systems:

  • The first is espagnolette (multi-point) locking, which are bolts (normally 3 sets) set into the window and located into locking points in the frame when the handle is turned. The bolts should be mushroom headed so that they can engage behind the locking point, thus enabling the window to resist being forced apart from the frame.
  • The second type is deadlock shoot bolts which locate into the frame at both opening side corners. There is also a deadlock which secures the opening side of the window at the handle. The window can also be fitted with high security friction hinges which locate into the frame on the hinge side.

For additional strength sections of hardened aluminium or galvanised steel reinforcements should be fitted at the time of manufacture within the hollow profiles of the windows and frames, so that the locking systems can be secured through the UPVC frames into the reinforcements.

It is preferable for the windows to be fitted with internal beading to avoid the possibility of the glass being removed from the outside. There are some systems which have external beading but are secure because the glass is adhered to the frame or secured by special tamper-proof clips, but in most cases internal beading is preferable.

Lastly, if you are considering replacing your existing windows, look for the new British Standard 7950 kite mark. It has been established to set specific manufacturing standards of design and security for windows.

Wooden casement

Illustration of Casement lock mechanism Fit locks which secure the frames together in preference to locks which simply secure the handle or stay bar. Casement windows, by their very design, need to be locked by securing the window to the frame. Most casement locks are screwed to the window rather than the frame – a weaker system. There are locks which are fixed to the frame and these are probably more secure, as well as being easy to use.

There are also locks specifically designed for use on windows with tapered edges (not 90º to the frame).

Illustration of rack bolt mechanism If the window is flush to the frame fit mortice rack bolts (bolts fitted into the window and operated internally with a key). They should always be fitted at 90º to the grain of the wood, reducing the likelihood of the wood splitting if subjected to pressure and fixed into either end of the frame. You might want to consider using door mortice bolts for a longer throw.

Illustration of push lock mechanism If you are intending to use the type of lock that screws to the window, the following test is a rough guide to help you to decide how many you will require: with the window closed, press each opening corner. If there is any movement, fit a suitable lock, such as a push lock (push to lock, key to open) at each corner on the opening side. If there is no movement, a lock fitted to the centre of the opening frame will suffice.

It is possible to secure wooden casements in the open position for purposes of ventilation, very necessary in hot weather, or child safety. These are particularly appropriate in a ground floor bedroom situation where someone wishes to sleep with the window open.

Likewise they are well suited to upper floors where windows can be locked open, allowing ventilation but, at the same time, preventing children from opening the window beyond a safe aperture. Whilst it is recognised that this type of device is designed more for safety purposes rather than security, it would be likely to alert the occupant if an attempt to force it was made. It is intended that these locks should be used only when someone is in residence. If your home is unoccupied the windows should be locked in the usual manner.

If you are considering replacing your existing windows, look for the new British Standard 7950 kite mark. It has been established to set specific manufacturing standards of design and security for casement windows.

Note: Georgian wired glass may look strong, but it will easily break. It is a fire safety glass not a security glass.

Wooden sliding sash

Illustration of sash stop mechanismYou cannot rely on existing central sash fasteners. Sash stops are strong and convenient to use and do not need to be removed from window when opening fully. They can be set into the top frame allowing the window to be left open about 5″ for ventilation but still secure. For optimum security fit in pairs.

Illustration of dual screw mechanismAn alternative form of lock is the dual screw. These in effect bolt the two sashes together. An added bonus is that, in so doing, they also reduce draughts.

The beading which holds the glass in place is frequently only pinned. The window can be made more secure, either by gluing in addition to pinning or screwing the beading, if wide enough, in place.

A modern style is the ’tilt to clean’ sliding sash, not only sliding up and down but also tilting inwards for cleaning by undoing two clips on top of each moving sash. These should be secured by fitting both sash stops and dual screws.