How do sash window locks work?

sash window

The sash window is a mainstay of British architecture, adding style and elegance to buildings for generations. A simple yet effective design, it consists of two vertical sliding glazed sashes and weighted cords.

Sash windows were appearing on a multitude of different buildings by the end of the 17th century, including royal palaces and prestigious heritage dwellings. Kensington Palace, Chatsworth House and Hampton Court were all adorned with stylish sash windows.

Sash windows’ growing popularity

Over time, the trend spread across Britain and sash windows were flourishing everywhere by the 20th century. This was partly down to their practical functionality.

They helped to keep the rain and draughts at bay, reducing the risk of frame-rot, as they closed to a narrower gap than hinged windows. The growth in popularity was also down to their visual appeal.

Architects enhanced the design further by adding two movable sashes to replace the fixed top. Glass manufacturing techniques also improved, with the panes becoming larger. The style of six-by-six panes became fashionable, as did Victorian decorative features, including mouldings and latticework incorporated into the structure.

Sash windows’ functionality

Sash windows need continued care to make sure they function properly and provide protection against the elements. In bygone times, they had wooden shutters to protect against draughts. Today, they tend to have blinds or curtains instead.

A sash window will continue to work at maximum efficiency when it’s well maintained. This includes the fasteners and locks. The most popular type of fastener is the lever arm sash. It comes in different widths to cater for very wide or narrow wooden meeting rails.

The lever arm fastener, fitted to the upper meeting rail, ensures the window’s panels remain closed and in position. It is ideally suited to well-maintained and correctly weighted windows. This remains the most commonly-used fastener, although other types have evolved in modern times.

How do the locks work?

Sash window security is extremely important. No matter what type of fastener is used, it should be available in a locking and non-locking version and in a variety of finishes.

The sash window locks work independently from the sash fasteners. They effectively stop the windows from being opened from the outside. The locks are fixed onto a vertical sliding sash window. Locks can be fitted whether the frame is made from timber, uPVC, aluminium, or any other material.

The locks are different from those used on a traditional casement window. Because the sash window slides open vertically, compared with outwards like a casement window, the lock doesn’t act as a handle. It merely restricts the sash window from being opened from the outside.

You need to slide the lock up to open the sash window. The casement window has hinges that permit the window to swing open, so the locks act as a handle as well. This is completely different from how sash window locks function.

What happens if you lose the key?

Sash stops are fitted to the window’s upper rail, while a small plate is fitted to the lower rail. This enables the window to be locked in an open position as well, to permit ventilation. A small key is used for the locking mechanism.

Sash window locks with restrictors that require a key to open the window are designed to be childproof, as well as burglarproof, so losing the key is a big deal.

Surface-mounted locks sit on top of the meeting rails and are appropriate for meeting rails of the same height. Should you break the lock, or suffer lost keys, you would need to employ the services of a locksmith, rather than risk damaging the mechanism.

The two main types of sash window locks have either protruding bolts that can be removed with a key or bolts that need to be extracted in the same way as dual screws.

The dual screws option will fit most sash windows, offering added security. This type of lock bolts through the top and bottom sashes to prevent the window from opening. The bolt is then removed with a key that comes included with the lock to permit the window to be opened.

The dual screws will lock the sashes into place to prevent them from sliding, even when the fastener is compromised. The full bolts are slightly more costly but offer extra protection.

Either way, it’s safer to employ the services of a local locksmith if you have window lock issues, as it can be a complex DIY task to repair old locks or fit new ones.