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Types of windows

The 8 Different types of windows (and frames) explained

There are many replacement window types, each with a different purpose which will be dependent on your style of home and your budget. As a guide, we list the 8 window styles,  including the variations and what they are best suited for so you can decide which windows you would like to install in your home.

Types of windows

What are the different types of window?

Hopper, Egress, Transom, Casement, Flush, Awning; there are so many different types of windows. Knowing your Bay from your Bow can be confusing and how do you choose which is the best window style for you?


Firstly, there are eight types of window in the UK:

Type of WindowDescription
CasementThe oldest and most versatile style that are usally side hung to open like a door, but can open from the top or bottom.
Tilt and TurnSide hung to swing fully open and bottom hung to tilt inwards for ventilation.
SashTwo panels that slide up and down, or one fixed panel and one sliding panel.
SlidingThe frame slides to the side like a mini patio door.
BayProjects out from the wall and extends to the floor with extended brickwork.
BowProjects out from the wall without any brick extension.
SkylightEither flush with the roof line or protrudes from the roof (dormer).
TransomThe window above a doorway, also known as a fanlight.

Within those main types, there are variations on how the window can open or how many different openers the window has. This makes a total of 17 different variations of window.


Every window style has its own uses and benefits. Some types of window are only suitable for specific applications, such as an egress window for fire safety, or a transom window for above a door. Others are more versatile, such as the casement.


When choosing a window, it’s important that the type of frame is in keeping with the age and style of the house. A traditional stone cottage wouldn’t look its best with uPVC tilt and turn windows. And a sleek contemporary new build wouldn’t feature sash windows.


As a guide, below are the 8 different types of window styles, including the 17 variations and what they are best suited for.


Window types

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Casement window


Casement window

The casement window is the oldest and most versatile style of frame in the UK.


Casement windows have a variety of options for configuration to suit most properties that can include single, double, triple (or more) panels. Depending on the size of the aperture.


Openers can be added to one side, both sides, top or full frame to offer different degrees of ventilation and the openers will shut with a tight seal for superior insulation and energy efficiency.


Casement windows suit most types of properties.


There are several types of casement windows:

  • Side hung
    Hinged at the side is the most common type of casement window and the opener will swing outwards.
  • Single casement
    The most basic window style has one frame and is usually side-hung.
  • Double frame or french casement
    Two side-hung casement frames with handles in the middle that open outwards to each side and create a large aperture (with central mullion).
  • Top hung or awning window
    Hinged at the top of the frame the window swings outwards from the bottom. This style is perfect for wet climates as they stop rain from entering the room.
  • Bottom hung or hopper window
    Hinged at the bottom of the frame the window drops open from the top of the frame. This allows plenty of ventilation and is a safer option for upper floor windows.
  • Flush casement
    The window opener closes flush into the frame to create a sleek appearance. Whereas a standard casement window opener sits proud from the frame when closed. The flush casement window is becoming increasingly popular as it offers a contemporary finish, especially in combination with a slim aluminium frame.

Tilt turn window


Tilt and turn window

The tilt and turn window became widely popular for uPVC double glazing when they were introduced in the eighties.


The major benefit of the tilt and turn is their ability to open in several directions and be securely left open on a tilt for ventilation.


Unlike the casement that opens outwards, the tilt and turn opens inwards and can be opened fully to allow for cleaning the external glass from inside a property. Perfect for windows on upper floors.


Tilt and turn windows have an incredibly snug seal when closed, making them one of the most energy efficient options of frame.


Tilt and turn have a thick frame and are less suitable for period properties where they can look out of keeping with the aesthetic of the property. House builds from the 1960s onwards and apartment buildings work best with tilt and turn.

Sash window


Sash window

Often considered to be the most aesthetically pleasing window that can add significant value to a house.


Usually fitted in period properties, with a concentration in London. Many listed buildings and properties in conservation areas are required to have sash windows that must be replaced on a like-for-like basis.


The standard sash window has two framed panels that slide up and down crossing over (although, some have one fixed panel, see below). Upper floors must have restrictors fitted as a safety measure.


The original design allows for a vented opening at the top and bottom of the window that can create a draw of air for superior ventilation. A clever design, long before we had air conditioning or extractor fans.


Unfortunately, old sash windows require significant maintenance and usually end up being painted shut in older houses. As the frames age, they create gaps that rattle in the wind and allow blasts of cold air. Cords become frayed and the sashes have to be propped open. Or, they become warped and stiff in the frames and can’t be pushed open.


Modern sash windows are constructed with spiral balances that allow easy opening and closing. Brushes that ensure a good seal when closed and can be double glazed for energy efficiency.


Well-fitted contemporary sash windows look stunning on a period property. Although they are an investment, they can make a property more desirable for sale.


Beware of removing sash windows from period properties as it can have a negative impact on the property value.


There are a few different types of sash windows:

  • Single hung
    One sash pane slides whilst the other remains fixed.
  • Double hung
    Both sash panes will slide open to allow venting at the top and bottom of the window.
  • Dummy Sash
    The window is styled to look like a normal sash window but the sashes are fixed and don’t open. Used to create symmetry and or equal sightlines on a property.

Sliding window or slider window

Instead of a traditional sash window opening vertically, a sliding window opens to the side, sliding horizontally. Imagine a mini patio door.


Sliding windows are usually made with a slimmer frame from aluminium which allows maximum glass area for a large bright window.


Perfect for the kitchen behind a sink where they can be easily reached to slide open. Also used for a kitchen window that opens onto a patio or terrace to allow for serving.


Sliding windows suit contemporary builds; especially for architecturally designed sleek homes. The use of large sliding windows and doors can open up spaces to the outside. For other traditional properties, one window might be installed in the rear kitchen but not used as a full set on the property.

Bay window


Bay window

A bay window projects out from the exterior wall line and extends to the floor.


Many Victorian and Edwardian houses feature bay windows as a focal point for the living room at the front of the house. Houses at the coast also benefit from the extra panoramic views from the projecting window.


They were designed as an ornamental feature, but also practically, to allow more ventilation from open windows on the sides that could capture more airflow into a room.


Bay windows can flood extra light into a room and are perfect as reading spaces to benefit from the light behind.


Because of the projection from the wall, a bay window is considered an extension. A replacement bay window or built at the back of a property is allowed under permitted development, but for a new window at the front of a property, it will require planning permission.


Types of bay windows

A bay window can have different configurations in the way it’s built. The most common are:

  • Single end bay - two windows with one edge and varying degrees of depth
  • Splay bay - like half a hexagon, three windows with angled edges
  • Circular bay - has five windows (or more) to create a circular effect
  • Square bay - has three windows with square edges

Bow window


Bow window

A bay window and bow window are similar and often confused. The clear difference between them is that for a bay window the base wall brickwork is also extended. A bow window unit projects from the room and ‘floats’ without the wall underneath.


Sometimes called a garden window, these bright spaces can have a shelf to grow plants or to just create an illusion of space.


Bow windows can be made up of several windows to create a curved effect and flood light into a room. At the front of property, they can take advantage of panoramic views or allow more visibility on a street.


Bow windows don’t require any building work to the base of the window or need planning permission.

Dormer window


Rooflight/Skylight window

There are two types of window you can have in a roof:


A dormer is a box protruding from the main roof, with its own roof. This creates more space in the room and the dormer creates more headroom for standing at the window.


Any type of small window can be fitted in the dormer window space.


A Skylight is flush into the angled roof and doesn’t protrude from the angle of the roof. Used in extensions such as kitchens, or dining rooms, the skylight can flood a room with light from an angled ceiling.


A skylight is a specific type of window that will fit into the roof and opens on a cantilever.


Sometimes known by the common brand name of Velux.


A series of skylights in an extension can offer maximum light into the room whilst retaining some insulation that a fully glazed roof would lack.


Skylights are more often used in contemporary builds or conversions whilst dormer windows look more traditional.

Transom window


Transom or fanlight window

A transom is the beam across the top of a door that separates it from the glass above. Hence, the transom window, also known as a fanlight.


Traditionally, transom windows were used above internal doors as a form of air conditioning in the home. The transom window opened above the door to create draw from a fireplace to move warmth to rooms upstairs. In summer, the front and back transom windows were opened to create air circulation to keep the house cool.


Fanlight windows were usually decorative featuring coloured glass and most often featured a sunburst pattern.

What is an egress window?

An egress window is not a style of window, but a safety measure. To ‘egress’ means to exit a building, so the egress window is a means of fire escape in an emergency.


For new builds or extensions, all rooms above, or below ground floor must provide at least one egress window (or door) that allows escape, or fireman’s access, in case of emergency.


Any style of window can be an egress window as long as it meets the building regulations: be more than 450mm wide or tall and have an openable area of at least a third of a meter square. The bottom of the window must be within 1.1 m of the floor in the room.

Types of window frame

Apart from style of frame, there are three main types of window frame material that you can choose from:


uPVC frames

Unplasticised Poly Vinyl Chloride, otherwise known as uPVC, has been the most popular choice for window frames since it was introduced in the late seventies, early eighties.


uPVC is low maintenance, energy-efficient and secure. It’s a durable material but low-quality white uPVC can stain if it's not cleaned properly.


uPVC windows are available in a wide range of colours and can have a textured wood-effect finish.


Aluminium frames

Aluminium allows for a much slimmer frame offering sleek styling. The slim style allows for a much larger glazed area with the appearance of a bigger window.


Often fitted on modern style builds because of their contemporary sleeker styling. The metal frame is not as energy efficient as uPVC but an aluminium window is very durable for a long-term investment.


Timber frames

Timber is a premium cost compared to other options but what you get is the unrivalled aesthetic of a beautiful wooden frame. For period properties, timber windows are often the only choice you should consider to be in keeping with the style of the property and to add value.


Timber is the most high-maintenance material, but quality hardwood that is looked after will have one of the longest lifespans of all materials.


Some properties in conservation areas and listed buildings will stipulate that you can only have timber frames. Always check before you replace windows.

What is the cheapest style of window?

The cheapest and most economical type of window is a standard side hung casement window in white uPVC.


Although, costs for windows are relative to the amount of windows, the size of the windows and the installation. So, only compare quotes for windows on a bespoke like-for-like basis.

Which type of window is best for my home?

When deciding which type of window is best for your home, it’s important to consider the style of your house and its surroundings to avoid creating confusion of style.


If you live in a period stone cottage, uPVC may ruin the traditional appeal. Whereas, a timber sash or casement window would be in keeping with the house.


A modernist new build might have large expanses of glass and slimline aluminium frames to enhance the clean lines of the architecture and flood the property with light.


Period properties that feature timber sash frames can be devalued if they are replaced with uPVC frames.


Think about:

  • What style of window was fitted in the original house?
  • What colour of frame best suits the colour of brick or stone?
  • What material is best suited to this type of house?

When replacing windows we would advise against choosing styles and colours based on current ‘trends’. There could be a fashion for certain colours of uPVC, but in 10 years, will this still look stylish or will it be dated?


Always try to choose what is most sympathetic and in keeping to the style of the original house from when the house was built.

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