Over 90 percent of homes in central London have sash windows. Millions more across the UK retain original Victorian, Edwardian and Georgian sash frames. Every sash window lock on the market does the same thing: locks the window shut. Cam fasteners, dual screws, sash stops and pressbolts all secure the sashes in the closed position. Some allow a fixed 100mm opening for basic ventilation. None offer an adjustable gap that the homeowner can set and lock at their chosen width. LockLatch is the only sash window lock that secures the window in the open position, with a stainless steel arm adjustable from 9 to 17 centimetres and a lockable pin that cannot be released from outside.
Why Sash Windows Need a Different Approach
Sash windows are inherently harder to secure than casements. The sliding mechanism creates natural weak points. Over decades, frames warp and sashes misalign, making traditional centre-rail fasteners unreliable. A cam fastener that does not engage properly because the sashes no longer sit flush provides no security at all. Dual screws drilled through both sashes are more secure but lock the window completely shut with no ventilation option.
Insurance requirements add pressure. Most UK insurers require key-operated locks on ground-floor and accessible windows. Many insurance policies do not yet specifically mention LockLatch by name, but the core principle holds: a break-in through a secured window is still a break-in. A lock that only works in the closed position forces homeowners to choose between security and fresh air.
Types of Sash Window Lock Available
Cam fasteners mount on the meeting rail and hold the sashes together when closed. They are the most common type, available from most hardware retailers. Sash stops fix into the frame at a set height to prevent the lower sash rising beyond a fixed point, typically 100mm for child safety. Dual screws drill through both sashes and lock them together with a key-operated barrel. Sash jammers are bolt-style devices designed primarily for uPVC but sometimes used on timber. Pressbolts push into the frame to hold sashes in place.
Premium options include key-locked stops that offer a fixed 100mm opening position, and vent locks that allow a push-release vent position but are not key-lockable. None of these products offer an adjustable, lockable open position.
The Security Problem with Older Sash Windows
A sash window that has been in place for 50 or 100 years has had decades to shift. The frame swells in wet weather and contracts in dry spells. The sashes no longer sit flush against the parting bead. The meeting rail, where upper and lower sashes overlap, develops gaps that a centre-rail fastener cannot bridge. The result is a window that appears locked but can be rattled open with sustained pressure from outside.
Even well-maintained sash windows have inherent vulnerabilities. The lower sash can be forced upward if the fastener is weak or misaligned. The upper sash, if it slides freely, can be pushed down from outside to create an entry point. Dual screws address this by physically bolting both sashes to the frame, but they lock the window completely shut. There is no intermediate position for ventilation.
What About Sash Jammers
Sash jammers are bolt-style devices that prevent a closed window from being forced open. They are widely available for a few pounds and are simple to install with two screws. But they were designed for uPVC casement windows, not traditional timber sash windows. On a sash window, the jammer can be fitted to the top rail of the lower sash to prevent it being pushed up. It works as a supplementary closed-position lock.
The limitation is the same as every other sash window lock: it only works when the window is shut. Open the window for ventilation and the jammer is disengaged. It provides no security in the open position and no adjustability. For a few pounds, it adds a layer of closed-position security. For ventilation security, it does nothing.
Insurance and LockLatch
Most UK insurers require key-operated locks on ground-floor and accessible windows. LockLatch is a relatively new category of product and is not yet referenced by name in most insurance policy wording. The practical principle, however, is straightforward: if someone breaks through a secured window, it is still a break-in and a covered claim. LockLatch adds a key-operated layer of security without replacing the existing lock on the window.
What LockLatch Does Differently on Sash Windows
LockLatch mounts with four holes to the window frame and sash, using either screws or rivets. It does not require drilling through both sashes like dual screws. It works even on misaligned frames because the adjustable arm bridges the gap between frame and sash. The opening can be set anywhere from 9 to 17 centimetres and locked with a pin that is only accessible from inside.
On a sash window, LockLatch works best in combination. One approach is to fit a sash stop or sash jammer to lock the top or bottom sash closed, then use a LockLatch on the other sash for secure ventilation. Alternatively, two LockLatches can be fitted: one holding the top sash slightly open but locked, the other doing the same for the bottom sash. This gives secure cross-ventilation through both sashes simultaneously.
For child safety, MiniLatch restricts the gap to 4.5 to 8 centimetres, within the 100mm threshold required by Approved Document K. Both products are C304 stainless steel, discreet enough for listed and period properties, and carry a lifetime guarantee.
Sash Windows in Period and Listed Properties
Approximately 75 percent of period homes in the UK retain original sash windows. Listed building consent is required for modifications, and planning authorities often insist that replacement hardware matches original design. LockLatch does not alter the window mechanism. It adds a supplementary lock with four small holes that can be filled if removed. Restored sash windows can increase property value by up to 15 percent. Proper security hardware protects that investment without compromising heritage character.
How to Choose
For basic closed-position security on a budget: a cam fastener at a few pounds. For a fixed 100mm child safety opening: traditional sash stops. For adjustable, key-lockable ventilation across any width from 4.5 to 17 centimetres, on any sash window, with stainless steel construction and a lifetime guarantee: LockLatch.
LockLatch ships from our distribution centres in the UK and South Africa.
Shop LockLatch now and let your sash windows breathe.
