How to Secure Sash Windows Against Break-ins
How to secure sash windows against break-ins
How to secure sash windows: sash stops, dual screws, locks and an alarm contact on every sash. No drilling, kit tested before shipping. Get my system proposal.
Box sash windows are part of what makes a Victorian terrace in Islington, a Georgian townhouse in Bath or a Clifton conversion flat so appealing. They are also, very often, the weakest point of the house. The original brass catch in the middle of the meeting rails was designed to stop the sashes rattling, not to stop someone with a thin blade. Here is the low-cost hardware the police recommend, and how an alarm fits around period windows without spoiling them.
The three weaknesses of a typical box sash
The central catch
Most period sashes rely on a single catch where the two meeting rails overlap. On older frames with a gap between the rails, it can sometimes be slipped from outside. Treat it as a draught fitting, not a lock.
Windows that open too far
A lower sash that slides fully up leaves a gap big enough to climb through. Upper sashes are often forgotten: on a basement or a back extension roof they can be within easy reach.
Hidden approaches
Lightwells below street level, side returns, flat roofs over a kitchen extension and wheelie bins pushed under a window all give a burglar cover or a step up. City of London Police point out that burglars have used ladders to reach upper windows that look unlocked.
Simple upgrades the police recommend
Both Avon and Somerset Police and City of London Police publish window security advice. The measures below come from that guidance; a Master Locksmith can fit purpose-made sash locks if you prefer not to do it yourself.
Sash stops, fitted in pairs
A sash stop is a small bolt fitted into the frame that limits how far the sash can slide. Fitted in pairs, they let you open the window a few centimetres for air while preventing anyone opening it enough to climb through.
Dual screws
A dual screw is a threaded bolt that passes through both meeting rails and locks the two sashes together.
Key-operated locks and restrictors
City of London Police recommend key-operated locks on ground-floor and other accessible windows, and opening restrictors that cannot be picked from outside. Locks only work if they are used: make checking them part of locking up at night.
Glass and replacement windows
For accessible windows, laminated glass or security film makes the pane much harder to get through. If you are replacing windows altogether, both forces suggest a security-accredited product tested to PAS 24:2022. In a conservation area or listed building, check with your local planning authority before changing frames or glazing.
Adding an alarm without spoiling the joinery
Good locks slow a burglar down; an alarm tells you the moment someone tries. Wireless sensors suit period windows because nothing is chased into plaster or cornicing.
- Opening contacts on each accessible sash: a slim magnetic contact sits on the frame and triggers as soon as the sash moves. Ajax DoorProtect Plus adds a shock and tilt sensor, useful for spotting someone forcing or tapping the glass.
- Upper floors too: extend coverage to first-floor rooms reachable from an extension roof, as City of London Police advise.
- A photo-verifying motion detector in the hallway confirms on your phone what triggered the alarm.
- Indoor siren and app alerts to the people you choose, with a backup battery and SIM in the hub if the power or broadband is cut.
Illustrative only. Your proposal is designed around your own house.
What we see go wrong
Keys left in the locks
A dual screw or lock key left in the frame, visible from the street, undoes the point of fitting it. Keep keys out of sight but close enough to open the window quickly in an emergency.
Painted-shut sashes
A sash painted shut feels secure but can trap you in a fire. Plan at least one usable escape window per floor and keep its key nearby.
Shutters left open at night
Original internal shutters with a bar add a real barrier and hide the room. Use them on basement and ground-floor windows when you are away.
An alarm only on the front door
Rear sashes and lightwells are far less visible than the front door. Cover the windows a burglar would actually choose, not just the obvious entrance.
Your kit, proposed online and shipped ready to fit
Tell us about your house on our proposal form or on WhatsApp: number of floors, which sashes are reachable, whether you have a lightwell or extension roof. A VISAO technician designs a system around it. When you order, we pair every sensor with the hub, name it by room, configure and test the whole kit before it ships. You fit it with adhesive pads following an illustrated guide, and a technician joins you on a video call to check each position and run the final test. See how it works, our solutions and the equipment.
Our team has 17 years in the trade and has worked for brands such as Decathlon, Audi and Louis Vuitton. Living in a period flat? Read wireless alarm kit for London flats or which alarm for a rented flat. For what happens when an alarm goes off, see police response to alarms in England.
Sash window security: your questions
Will alarm contacts damage original sash windows?
No. Wireless contacts are fixed with adhesive pads to the frame and sash, so there is no drilling or wiring. They can be removed later, which matters in a rented or listed property.
Can I still open the window for air with the alarm on?
With sash stops fitted you can leave a window slightly open for ventilation. Tell us which rooms you like to air at night and we will plan the sensors and arming modes around it.
Do I need permission to add locks in a listed building?
Rules vary from building to building. If your home is listed or in a conservation area, check with your local planning authority before altering frames or glass.
Keep the sashes, lose the weak spot
Describe your house in a few lines. We send you a tailored system proposal and, once you approve it, prepare, test and ship your kit ready to fit.
Hardware advice based on published guidance from Avon and Somerset Police and City of London Police.
