All About Sash Windows | SashWise

All About Sash Windows

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At SashWise we’re slightly obsessed with sash windows, having been in the business since 2006. We thought it was high time that we shared some of our knowledge, and we hope it helps you to decide what type of sash window services are right for you.

What are sash windows?

The word sash refers to one of two moveable panels that comprise the window. The panels slide over one another vertically, running in a frame and controlled by sash cords. There are several different types of sash windows, but they all work on the same principle.

Traditional Victorian and Georgian sash windows found in London are usually multi-panelled. These days using modern building practices it is possible to replicate the look of original sash windows with new double glazed sash windows.

How do sash windows work?

Close up shot of gold hardware on a window

The two sashes slide over one another vertically, controlled by a cords which run over pulleys and counterbalanced with metal weights.

The counterbalancing makes them feel lighter and easier to open and close. In all sash windows, the bottom sash can be slid upwards. In double-hung sashes, the top sash can also be slid downwards.

The sashes can be clasped together in a closed position using a sash fastener situated on the top of the bottom sash. There’s usually also a stop lock for additional security, which prevents the window from travelling too far upwards and bottom sash lifts to aid raising the lower sash.

History of sash windows

Here in South West London, where SashWise are headquartered, you’ll find thousands of houses from the Georgian and Victorian eras with sash windows. In fact, some of the earliest examples of sashes can be found at Ham House, just around the corner from us.

Ham House, Richmond upon Thames

Ham House – an early adopter of sash windows

It’s thought that sash windows were invented in England by architect Robert Hooke. They offer a very large area of opening and part of their design may have been to allow a quick and easy escape route in the event of fire – something very much on the minds of building designers in London, particularly after the Great Fire of 1666.

The distinctive Georgian style of 6-panelled sashes, normally arranged in two rows of three panes, came about partly because of the technical difficulty of making large single panes of glass. Later, as glass became stronger and cheaper, larger single panes could be used.


Sash windows can be constructed from softwoods or hardwoods or plastic materials such as UPVC.   At Sashwise we only work with timber sash windows, not UPVC.

Double-glazed sash windows

Today, all new sash windows are construction incorporating double-glazed glass, to meet with modern Building Regulations which stipulate minimum standards of thermal efficiency. Double glazing has many other advantages beyond keeping heat in, including reduced noise pollution.

Refurbishing sash windows

Refurbishing sash windows


As beautiful as they are, sash windows suffer from some common problems, especially older or original ones.

They can jam when their wooden boxes expand or are painted over or when dirt builds up between the sashes and the surrounds. The opposite problem occurs when the sashes become loose within their boxes causing drafts, rattling and uneven running.

The window frames and sills can become rotten or overpainted.

The internal cords can fray and break or become dirty and unsightly. And they can allow cold air or even rainwater in.

All of these problems can be fixed by sash window refurbishment, which involves removing the window from its box, stripping, sanding, and repainting the boxes and sashes, replacing the cords, cleaning the windows, repairing the joints, and refitting the windows.

Sash window restoration is a specialist job, which here at SashWise we have a highly skilled team of craftsmen with over 25 years of experience between them, that can restore sash windows to their former glory.


At SashWise we offer a wide range of services to ensure your sash windows look beautiful, are well maintained and work efficiently.

We specialise in the restoration, replacement and reinstatement of traditional timber sash windows.

We also specialise in dealing with rot repair and enhancing the security of your sash windows. We can also completely replace your sash windows with new Accoya hardwood double glazed sashes, and we can repair or fully restore your original windows.

Photo credits:

Ham House: File:Ham House 2007.jpg – Wikimedia Commons