Window locks and insurance — what UK insurers require

If your home insurance renewal mentions window locks, or you've had a quote that hinges on your windows being "secured to British Standard", you're not alone in finding the wording confusing. Window locks insurance clauses are one of the most misunderstood parts of a home policy — and one of the easiest ways to have a claim reduced if you get it wrong. This post explains, in plain English, what UK insurers actually expect, which windows are affected, and what happens to a claim if a window is left unlocked.

Why insurers care about windows

Burglars are opportunists. A surprising share of break-ins happen through windows rather than doors, and an unlocked or poorly secured window is one of the quickest ways into a property. Insurers know this, so they price the risk into your premium and, in return, ask you to keep accessible windows locked.

The logic is simple. A key-operated window lock turns a window from a thirty-second entry point into a real obstacle. Even if a burglar smashes the glass, a locked window often won't open far enough to climb through, and the noise and effort put many off entirely.

That's why the security clause in your policy almost always covers windows as well as doors. The same thinking sits behind door lock standards too — we cover those in BS3621 explained.

Which windows actually need locks

The key word in almost every policy is accessible. Insurers don't usually expect you to lock a third-floor window that no one could reach without a ladder. What they care about are the windows a burglar could realistically climb through.

In practice, "accessible" means:

• All ground-floor windows, front, back and side.
• Basement and semi-basement windows.
• Upper windows reachable from a flat roof, such as those above a kitchen extension or single-storey rear addition.
• Windows reachable from a drainpipe, porch roof, garage roof, wheelie bin or garden structure.

This last category catches people out. A first-floor bathroom window directly above a flat-roofed extension is "accessible" in insurance terms, even though it's a floor up. The same goes for a landing window beside a sturdy drainpipe.

Manchester's housing stock makes this very relevant. Victorian and Edwardian terraces around Didsbury and Chorlton often have rear kitchen extensions with flat roofs, putting a bedroom or bathroom window within easy reach. If you're unsure whether a particular window counts, the safe assumption is to lock it.

The types of window lock

What you need depends on the window itself.

Timber sash windows

Traditional vertical sliding sash windows — common in period terraces — are usually secured with sash stops (also called sash bolts or Brighton fasteners with a key). A keyed sash stop screws into the upper sash and, when engaged, stops the lower sash sliding up past it. Fitting two per window, one each side, is the usual approach.

Timber casement windows

Side-hung casement windows take key-operated casement locks, sometimes called cockspur locks or mortice rack bolts depending on the design. These bolt the opening sash to the frame and need a key to release.

uPVC and aluminium windows

Modern uPVC and aluminium windows almost always have a built-in espagnolette or shootbolt mechanism — the strip of locking points along the edge of the opening sash that engages when you lift the handle. The security comes from the handle being key-operated and lockable. If your uPVC window has a handle that locks with a key, you're generally already compliant; if it has a non-locking handle, swapping it for a locking one is a quick, cheap job.

Locking restrictors

For windows you want to leave open a crack for ventilation — handy in a child's room or for airflow in summer — locking restrictors allow the window to open a few centimetres but no further, and lock in that position. These are also valuable as a child-safety measure.

"Minimum security" clauses vs "warranties" — the crucial difference

This is the part that matters most, and the part most homeowners never read.

A general security condition (sometimes called a "reasonable care" or "minimum security" condition) asks you to fit and use the specified locks. If you fall short, the insurer looks at whether the failure was connected to the loss and behaves reasonably about it. There's usually some give.

A security warranty is far stricter. A warranty is a promise that something will always be true — for example, that all accessible windows will be locked whenever the home is unoccupied. If you breach a warranty, an insurer can, in principle, decline the claim even if the breach didn't directly cause the loss. Consumer protection rules have softened the harshest outcomes, but warranties still carry real teeth.

The practical takeaway: read your policy wording and look for the word "warranty" or phrases like "it is a condition precedent". If you see them, treat the requirement as absolute.

What happens to a claim if a window was left unlocked

Picture the common scenario. You pop out, leave a rear window on the latch for the cat, and come home to a burglary through that window.

If your policy required accessible windows to be locked when the property is unoccupied, the insurer will look at:

• Whether the window was an accessible one the policy covered.
• Whether it was actually unlocked at the time (forced-entry signs, or the lack of them, tell the loss adjuster a lot).
• Whether the breach was a condition or a warranty.

Where it's a warranty, or where the unlocked window was clearly the point of entry, a claim can be reduced or refused outright. Where the wording is softer and the loss wasn't connected to the lapse, you may still be paid. It's a gamble you don't want to take — fitting locks and using them removes the risk entirely.

It's worth understanding how burglars actually choose and exploit weak points, which we explain in how burglars open doors. Windows are firmly on their list.

What it costs to put right

Window security is one of the cheapest upgrades in home security.

• Key-operated window locks supplied and fitted: roughly £15–£40 per window for the lock, plus labour.
• Locking uPVC handles: typically £20–£40 each fitted — often all a modern window needs.
• Whole-house visit: most properties can be brought up to standard in a single appointment, which keeps the labour cost sensible per window.

Compare that to a refused burglary claim and the maths is obvious. We can also advise on which windows genuinely count as accessible so you're not paying to lock windows no insurer would worry about. See our lock replacement service for window and door security work.

A note on keys and fire safety

One sensible habit: keep window keys nearby but out of sight from outside — not on the windowsill or dangling from the lock. In a fire you may need a window as an escape route, so everyone in the household should know where the keys live. For bedrooms used by children or vulnerable people, a keyed lock plus a kept-nearby key strikes the balance between security and a quick getaway.

When to call a locksmith

It's worth calling a locksmith if:

• Your insurance renewal or new quote specifies window locks and you're not sure what you have.
• You've got timber sash or casement windows with no key-operated locks at all.
• Your uPVC handles don't lock with a key.
• You've just moved in and don't know whether the previous owner met the policy requirements.
• You've had a break-in or attempted entry through a window — see our burglary repairs page.

A locksmith can survey your windows, tell you which ones an insurer would class as accessible, and fit the right locks in a single visit. It's a small job that protects both your home and your ability to claim.

If you're in Manchester and want your windows checked against your policy wording, get in touch. We'll tell you honestly what you need — and what you don't — before any work begins.