It’s only when you start window shopping that you realise how many types and styles there are to choose from. 

In this article, we’ll guide you through the main window opening types, frame shapes and how the bars that divided the panes can influence a window’s aesthetics. 


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Casement and sliding sash – the main window opening types
Which is better, sash or casement?
Advantages of casement windows
Advantages of sliding sash windows
Window shapes
Glazing bar designs
Casement glazing bar styles
Sliding sash glazing bar styles
Casement window styles
Sliding sash window styles


Casement and sliding sash – the main window types

The two main window types are casement and sliding sash. Which you choose depends on how you’d like your new windows to look and operate. Planning requirements based on your property and the area you live in, as well as your budget, may also play a part in your choice.


Casement window


Sliding Sash window


Casement windows swing open using hinges on one side of the window frame. 

  • Depending on where you put the hinges, the window can open inwards or outwards. Generally. people prefer their windows to open outwards.

  • Top hinges create an ‘awning casement’ (opening outwards).

  • Bottom hinges create a ‘hopper casement’ (opening inwards). 

  • ‘Direct glazing’ sets the glass directly in the wooden frame without a sash and therefore doesn’t open.

Vertical sliding sash windows open by sliding up and down on a track within the frame. 

  • There are usually two panels set one above the other, called sashes. 

  • When both sashes can slide, it’s a double-hung window. 

  • When only one sash moves, it’s a single-hung window. 


Which is better, sash or casement?

Neither window type is better or worse than the other. Instead, it’s about which is best for your personal preferences and property. 

Questions worth considering:

  • Which style will fit most naturally with the look of your home?

  • Would you like your new windows to match the style of your old ones? Do planning conditions require that they match?

  • Do you have limited space or other operational requirements that could make one style more practical than the other?

  • Is ventilation a top consideration? Sliding sash windows are designed to promote improved airflow even on still days by moving cool air in and hot air out simultaneously.


Advantages of casement windows

  • Casement windows offer a modern, contemporary look (depending on the chosen design options).

  • Ideal for new builds and renovations.

  • Casement windows with lipped casements (e.g. stormproof) generally provide better protection against the weather than sliding sash windows

  • Usually less expensive than sliding sash windows because of their simpler construction.

  • Readily available in more sizes and shapes than sash windows. 

Advantages of sliding sash windows

  • Sliding sash windows offer a traditional style that’s the perfect match for historic and period homes, e.g. Georgian and Victorian.

  • Can open even if space outside the window is restricted (e.g. a wall or tree nearby).

  • More flexibility in how the window is opened than casement, e.g. separating the inflow and outflow by equally opening the top and bottom creates maximum ventilation


Window shapes

A well-chosen rectangular frame can be the perfect choice for a modern or traditional home. But sometimes, special projects deserve an extra splash of creativity in the form of custom-shaped window frames.  


Circular, triangular, arched...even pentagonal windows can add a wow factor or provide the ideal solution for an opening of unusual proportions.


Glazing bar designs

You can give the same window a completely different look by altering its glazing bars arrangement (the strips that separate the panes of glass). 

Casement glazing bar styles


Without any glazing bars, a casement window looks minimalist, modern and offers an unobstructed view. Adding a four-over-one arrangement can transform the window into a Victorian-style frame. Or adding a couple of horizontal bars to two taller panes can give the window an elegant, deco-themed appearance. 

Your glazing bar options are practically unlimited, so think about which period or style you would like to evoke.


Sliding sash glazing bar styles



Victorian Bar


Cottage Bar


Horizontal Bar


Deco Bar


All Bar


In the 17th and 18th centuries, there were no formal names for sliding sash windows’ unlimited pane configurations. Today, we describe them by the number and arrangement of panes. For example, a one-over-one sash window has one large pane set above another pane of equal size. 

There’s also a range of popular glazing bar styles that are reminiscent of specific historical periods, e.g.:

  • Queen Anne Revival. A six pane upper sash with a single pane bottom sash (see Victorian Bar above).

  • Late Victorian. Typically simpler, with either single panes or a two-over-two vertical split glazing pattern (see Vertical Bar above).

  • Georgian. Glass was limited to small panes in the Georgian period, so 12-over-12, nine-over-nine, eight-over-eight, etc., pane configurations were popular (see All Bar above). 

Casement window styles

There are several casement window styles to choose from. 




Victorian Bar


Marginal Bar


Vertical Bar


All Bar


A stormproof casement window has a lipped casement that rests ‘proud’ of the window frame. In other words, the part of the window that moves isn’t flat to the surrounding frame when the window is closed. 

This style is sometimes called a ‘storm casement’ because the lip offers added protection against the weather.
View our most popular Stormsure casement timber window.


A flush casement window has a sash that fits flush with the frame. The whole window, inside and out, is flat when closed. 

Because they were a hallmark of Georgian, Victorian and Edwardian homes, flush casement windows are an excellent choice if you live in a traditional property or conservation area. 

As with other window styles, flush casements can be customised using various glazing bar configurations. 
View our Elegance flush casement timber window.


Our Regency casement window blends the functionality and energy efficiency of a casement window with the appearance of a sliding sash window. 

Although the window opens outwards like any other casement style, the addition of decorative horns evoke the look of a sliding sash window. 

If you like the sliding sash window style but have a tight budget, this window offers a low-cost solution. 

View our Regency casement window.

Sliding sash window styles

As well as customising the sliding sash window’s size, pane configuration, colour and glazing, you can choose between two types of opening mechanism. 


Sliding sash (modern features)

This window combines the traditional appeal of a sliding sash window with modern design features.

It has stepped sashes for improved performance, a tilt-in facility for easy cleaning and maintenance, and class horn detailing on the top sashes. This style is ideal whether you’re renovating a character property or planning a traditionally designed new build. 

It uses a traditional fitch catch and spiral lift balance mechanism as standard but can be fitted with an assisted lift spiral balance as a special order. 

View our vertical sliding sash timber window.


Box sash (traditionally operated)

This high-specification box sash window is traditionally operated with a true weights-and-pulley system. It’s an ideal direct replacement for an original box sash window in a period property.  

Traditional sash horns and a choice of glazing bar designs give you total freedom over the final look, while low-E double glazing as standard provides impressive energy efficiency. 

View our box sash timber window

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