How to Make Your Windows More Secure Against Break-Ins
How to Make Your Windows More Secure Against Break-Ins
Windows represent one of the most vulnerable entry points in any home.
They account for roughly one in five domestic burglaries in the UK.
Intruders can target several weak spots, depending on the type of window.
And they often rely on speed and silence. Locks, reinforced glass, and alarms often reduce their chances of achieving either of these.
Fit key-operated window locks
Further reading
Key-operated locks are a solid basic form of home window security.
Unlike latches, they require a key. This stops one of the simplest intruder methods: Breaking a glass pane and reaching inside to turn a handle.
(This is why you should always store window keys out of sight of the window.)
You should fit key-operated locks to all ground-floor windows and easily accessible upper-floor windows, i.e., ones reachable from:
- Flat roofs
- Balconies
- Low boundary walls
- External drainpipes.
Secure your sash windows
Traditional timber sash windows slide vertically within their frames.
As most long-term owners of these windows know, it’s easy to accidentally knock these off their frames.
So, it’s even easier to purposely do it, hence them being a frequent target for opportunistic intruders. A thin tool inserted between the meeting rails often does it.
To secure them against forced entry, install specialized secondary hardware:
- Sash locks: Key-operated locks mounted across the central meeting rails where sashes overlap.
- Barrel locks: Metal cylinders go into holes drilled through the inner sash frame. This prevents movement until you remove the locking pin with a key.
- Sash stops: Heavy-duty metal pegs or bolts fitted into the upper frame track that prevent sashes from opening wide enough for an intruder to climb through.
- Sash jammers: Metal arms mounted on the window frame that swing over the sash edge to hold the window firmly shut.
Fitting a combination of these allows you to safely leave sash windows partially open for ventilation.
Real-World Case: When Window Restrictors Work
In 2020, a burglar attempting to climb through a Swindon property window got his leg wedged in the frame. This left him stuck hanging upside down. He had to dial 999 himself to request a fire crew rescue before he was promptly arrested.
Fitting sash stops or window restrictors keeps window openings under 100mm. They are narrow enough for ventilation, but tight enough that opportunists end up trapped or turned away.
Secure your UPVC windows
Modern UPVC windows often have built-in security, but poor maintenance or broken handles can leave your property exposed.
Most UPVC casement windows rely on an espagnolette bar mechanism (commonly called an espag bar). This is a flat metal rod running with multiple rotating studs inside the inner frame.
Turning the window’s handle slides this rod and pushes the metal studs into plates mounted in the outer frame.
Espag bars require maintenance. If the handle feels loose or the studs don’t engage smoothly, replace the internal mechanism.
Sash jammers also reinforce UPVC windows’ security. They are small metal arms secured to the frame that pivot over the opening sash.
Further reading
Secure windows from the inside
This improves home protection without altering external building aesthetics.
Window stops are a great way of doing this. They are heavy-duty clamp stops or screw bolts that attach directly to internal window tracks, restricting how far a window can open from inside.
You can also apply clear security film on the inner window surface. This polyester layer holds the glass together if it’s broken, slowing entry and creating noise in the process.
It can be applied using a squeegee and soapy water, and it leaves the window’s appearance unchanged from the outside.
Secure ground floor windows specifically
Ground-floor or basement windows face the highest risk of forced entry.
From this level, potential intruders can even take part in ‘window shopping’ for visible valuables. They can also easily notice unlatched handles or absent security alarms.
Never leave ground-floor windows open or unlatched when you’re out. Keep valuable items completely out of sight from ground-floor windows.
For ground-floor windows in particularly vulnerable locations, consider fitting steel security grilles or collapsible window bars.
This includes basement lightwells or side alley windows that are hidden from street view (and therefore give intruders more confidence to attempt).
Collapsible grilles slide along internal tracks. This allows you to fold them back when you’re in and lock them in place when you’re out (or sleeping).
Why the UK Doesn’t Use Window Bars — And What to Do Instead
In China, steel security bars on lower-floor windows are common sights in cities. They typically cover every window of buildings up to the third or fourth floor.
However, several fatal fire incidents in China prompted cities including Guangzhou to ban fixed bars in new builds and require quick-release emergency mechanisms on existing ones.
UK homeowners wanting the same deterrent effect can also fit collapsible security grilles instead. These lock securely from the inside but can be released quickly in an emergency — the security benefit without the fire risk.
Fit window alarms
Window alarms trigger siren when pressure is placed on the window or when it’s opened. The noise itself scares off most intruders.
There are two main types worth knowing
Magnetic contact alarms
These are simple battery-powered alarms that are easy to install by yourself.
They have two magnetic components, one fitted to the window frame, one to the opening sash. When the window opens and separates these, the alarm is triggered.
Vibration or glass-break sensors
These mount directly onto the glass and trigger on impact. They’re useful where a contact alarm isn’t practical (e.g., for fixed glazing panels or skylights).
Like magnetic contact alarms, these are widely available from hardware stores and don’t require professional installation.
Historical Case: The "Child-Sized" Entry Point
Using small openings to breach a home is one of the oldest tricks in British ‘housebreaking’ (as burglary used to be known). In Dickens’ Oliver Twist (1838), the villain Bill Sikes famously forces young Oliver through a tiny ground-floor pantry window that most adults couldn’t fit through.
Small-framed burglars exploiting tight openings was a real-world staple of 18th-century London. Jack Sheppard (widely credited as the origin of the phrase “Jack the Lad”), was a slender thief who routinely squeezed through narrow window bars and cellars. He used those same tight openings to pull off four infamous prison escapes!
Additional security measures
Security film
Clear polyester security film adheres to the inner glass surface. It provides anti-shatter glass protection.
Laminated glass
This consists of two glass panes bonded around a tough polyvinyl inner layer.
It also holds broken glass fragments in place, preventing easy entry and creating noise that alerts neighbours.
PAS 24:2016 accreditation
If you plan to replace existing window units, select products carrying PAS 24:2016 accreditation.
PAS 24:2016 is a British Standard benchmark for thief-resistant window assemblies.
Accredited windows undergo independent evaluation of:
- Frame structural strength
- Glass bead retention
- Resistance to forced leverage
And more.
Further reading
External deterrents and foliage maintenance
Intruders prefer targeting windows concealed behind overgrown hedges or shrubs.
Pruning back foliage around ground-floor windows maintains clear sightlines from the street.
Security lighting that’s activated by movement and clearly displayed alarms and cameras also help.
What your home insurer requires
Most UK home insurance policies include strict window lock mandates within their policy terms.
Insurers typically require key-operated locks on all ground-floor windows and accessible upper-floor windows.
Policy agreements frequently reference BS 7950, a standard specifying security performance requirements for domestic windows.
Without it, your insurer may reject your contents or buildings claim entirely.
Review your home insurance documents or contact your provider to verify your policy’s exact hardware requirements.
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