Flat Roof Extension Design Ideas

17th September 2021

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Flat roof extensions have had a huge resurgence in popularity over recent years. While once they were plagued with negative connotations, a flat roof extension is now one of the most contemporary and desirable home improvements there is.

If you are starting to plan your flat roof extension, you may be looking for design ideas. Many homeowners think there is only one design available to them if they have this type of extension, but this is not true. There are a number of ways that you can personalise a flat roof extension design to make it perfect for you and your home.

Here are the top 3 flat roof extension design ideas:

1. Roof Glazing

At number one is roof glazing. While flat roof extensions used to typically have a solid roof, these days there are many ways that you can flood the room below with natural light, while also adding a wow factor to your new extension. The most popular choices to do this are to add flat skylights or lanterns.

Flat Skylights

Flat skylights (as their name suggests) are a large flat window on the roof of an extension. They give a very modern look to a flat roof extension and are available in sizes up to 2.5m in length. Flat skylights sit atop of what is known as a kerb. From the inside, this means that they are set up into the plastered area of your extension. This elevated setting means that although they are very simple in design, flat skylights can certainly add the wow factor to your new living space.


Another popular choice for glazing is a lantern – or several lanterns if you wish! A lantern is like a miniature conservatory roof, featuring a number of pieces of glass that slope downwards away from a central pitched ridge. In the past lanterns were used on traditional orangeries, but modern lanterns are very sleek in design and make a great addition to a modern extension.

2. Doors

At number two is doors. As the popularity of flat roof extensions has soared, large spans of modern doors have become a key staple in most designs. While bringing in vertical light from above via flat skylights or lanterns is the best way to flood your room with natural light, large spans of doors also bring in a huge amount. Bi-folds have been the ‘door of choice’ for homeowners for many years now. They are large – bringing in large amounts of light, and they can be opened to create a large opening between the home and garden. Commonly chosen in anthracite grey or black, bi-folds are a fantastic way to give your flat roof extension that ‘Grand Designs’ look. Also popular are large spans of sliding doors. As with flat roof extensions, sliding doors are enjoying a resurgence in popularity. While patio doors were once considered a very functional product, new modern designs and using them in large sizes means that they have been given a new lease of like – and make the perfect addition to a modern flat roof extension.

3. Claddings

Finally at number three is claddings. Flat roof extensions will tend to have two or three external faces and it’s important to think about how you will finish these. While your extension will feature doors and windows, how you finish the external solid areas around these can add that special touch to the look of your new extension.

Ultraframe extensions can be clad in any external finish that you choose. Think carefully about the materials and colours that you choose. As well as choosing a cladding or external finish that looks beautiful, think about maintenance and durability. For example, cedarwood cladding is very popular as a cladding for home extensions and looks very beautiful when first installed. However, it weathers quickly and needs regular maintenance to keep it looking good. Alternatives to consider which require less maintenance and are more durable include PVC cladding and render. Both of these options are available in a range of colour choices, allowing you to finish your flat roof extension to either complement or contrast with the rest of your home.

While the three options above are key factors that will enhance the design of your flat roof extension, there are of course many other things to consider when planning such a home improvement. These include:


The shape of your extension. Square or rectangular are the options available when choosing a flat roof design. Which one will work best for you will depend on the function of your room, the space available to build the extension, and of course, your budget! Ultraframe extensions can be used to create a flat roof extension in a matter of days thanks to the unique technology within the system.


Will your flat roof extension be open plan to another room in your home or a separate room? Of course, the main function of your extension will largely influence its design – will it be a kitchen, a lounge, both?


While it’s vital to ensure lots of natural light for a bright, airy room, think carefully about the lighting you add to your room too. Aside from your main lights, consider adding lamps for atmosphere and light just where you need it.


Linked to the point above is electrical sockets. An extension design needs to be thought about carefully, right down to this level of detail! Try to work out during the planning process where you will place lamps and other electrical items and ensure you include plenty of plug sockets in your design. It is far easier to include them at the build stage than afterwards when your walls are newly plastered!


Colour is another key consideration when planning any home extension. Not just the external colours of the roof, windows/doors and cladding – but the internal colour theme. Colour affects our mood and the atmosphere of a room massively so choose wisely! For example, a white room is cool and calming but some may find it uninspiring.

A dark room or wall is dramatic and can surprisingly, give a very cosy feel to a space. Green is a soothing inspiring colour and links to the garden beyond your extension. You may choose to be bold with coloured feature walls or inject subtle splashes of colour with soft furnishings – the choice is yours.

There are many other things to consider when designing a flat roof extension and your design ideas may evolve during the planning process as you come across different ideas and things to inspire you. Ultraframe extensions are faster to build, highly energy efficient, of a consistently high quality, less messy to build, and can often be started sooner due to the speedy timelines. If you’re currently working on your flat roof extension design, make sure you consider Ultraframe!

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