The front door gets all the attention — the heavy locks, the anti-snap cylinder, the smart doorbell. Meanwhile, the windows are often the genuinely weak point, and burglars know it. A surprising number of break-ins happen through a window that was either unlocked or fitted with a lock that barely slowed anyone down. The good news is that securing your windows is one of the cheaper, higher-impact upgrades you can make. Here is how window security actually works, where the weak points are, and what is worth fitting.
Windows attract intruders for simple reasons: they are often left on the latch “just for air,” they are sometimes hidden from the street by fences or shrubs, and older ones can be opened with very little force. The ground floor and the rear of the house are the favourite targets, because that is where a window is both reachable and out of sight. Upper-floor windows are not immune either — the police note that burglars will use a ladder found in the garden to reach an upstairs window left open, specifically to get above the alarm sensors downstairs.
Not all window fastenings are security devices. A plain window catch or latch holds the window shut against the wind but offers almost nothing against a determined intruder — a small hole and a bit of wire can flip many of them open. Standard sash fasteners are similar: convenient, but a little brute force or a simple tool often defeats them. If your windows only have catches like these, they are effectively unlocked from a security point of view.
There is also an older design flaw worth checking. On some early uPVC windows the glazing bead — the strip that holds the glass in — was fitted on the outside. That let a burglar quietly prise the bead off and lift the glass out without breaking anything. Modern windows have internal beading; if yours are old, it is worth checking.
The single most effective and affordable upgrade for most homes is a key-operated locking handle. It is easy to use, it resists forcing, and — because it is visible from outside — it works as a deterrent: most burglars will not risk the noise of breaking glass to reach a lock they still cannot open. On modern uPVC and timber windows you will often already have an espagnolette (“espag”) handle, which throws hooks or bolts into the frame at several points when you turn it. A multipoint mechanism like this is far stronger than a single catch, because there is no one point to lever.
Where security really matters, look for a recognised standard. Window locks carrying BS3621, and replacement windows tested to PAS 24, have been independently assessed against common attacks — and your insurer may well require key-operated locks on ground-floor windows as a condition of cover. The same British Standard thinking that applies to door locks, which we cover in our British Standard locks guide, applies to windows too.
Restrictors limit how far a window opens. They let you have a window ajar for ventilation while stopping it from opening wide enough to climb through, and they are a cheap, retrofittable win on most window types. Sash jammers do a similar job on sash and uPVC windows, blocking the window from being forced or lifted out. They double as child-safety devices, which is a useful bonus on upper floors.
Never restrict or lock every window so tightly that no one can get out in a fire. Keep at least one easily-openable window in each room as an escape route, and make sure everyone in the house knows where the keys are kept.
A locked window is only secure if the key is not sitting in the lock. Remove keys from locked windows so they cannot be reached through a small broken pane — but keep them close by and known to the household, both for daily use and for escape in an emergency. A small, consistent spot near each window (out of sight from outside) is the usual compromise.
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Good window locks work best as part of the whole picture. Combine them with the door security, lighting and habits in our guide to preventing burglary, and you remove the easy opportunities that most break-ins rely on. If you are not sure what your current windows are fitted with, or whether they meet your insurer’s requirements, a locksmith can assess them and fit the right locks — usually a quick, inexpensive job that closes off one of the most overlooked ways into a home.
Real break-ins are fast, quiet and practical — and they cluster around a handful of methods. Each one explained by the locksmiths who repair the aftermath, with the specific fix.
For the jobs best left to a pro, your local locksmith network has you covered nationwide.
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