Interior Designer-Approved Tips and Tricks for Creating Your Dream Extension

Whether you’re dreaming of a sun-filled open-plan kitchen or a multifunctional family space, getting the design details right can transform your extension from an add-on into a seamless part of your home. 

When it comes to beautifully designed extensions, the devil is in the detail, so who better to look to for advice than interior designers themselves?

Here Athina Bluff, founder and studio designer of Topology and Wren Loucks, founder and creative director of Be-kin, share their interior tips for creating an extension that ticks all the beautiful and practical boxes.  

The importance of interior design for extensions

The interior design of your extension is just as important as the build itself. While structural elements create the space, it’s thoughtful design that transforms it into rooms you’ll love to live in. A well-planned new extension equates to a space that flows naturally from your existing home, maximises natural light and creates practical, inviting areas that work for your lifestyle. 

From choosing the right colour palette and lighting to picking materials that evoke atmosphere, interior design decisions impact how you’ll feel in your new space every day. Athina advises that natural textures like wood, linen and stone can create a cosier feeling than metal and glass, for example, while colour choices should take the direction the room is facing into consideration.

As well as aesthetics, smart interior design can make a space feel larger and more welcoming,  turning your extension from an add-on into an integral part of your home that you can’t believe wasn’t there in the first place. As Wren puts it, “it makes spending time together as a family more relaxing and fun”. 

Choosing a layout for an extension 

Choosing the layout is a big decision, so it’s natural to go round in circles a bit. Rather than following trends, first focus on you and your household’s daily patterns: how you move through spaces, where you naturally gather and what frustrates you about your current layout. The designers find that most of their clients use their extension to create open-plan kitchen and dining areas to be enjoyed by everyone. A key thread is improvements that make daily life easier (like being able to cook while watching the kids play) or multifunctional zones that do different jobs throughout the day – like a home office-snug.

Consider the path of natural light throughout the day, views into and through the space, and how the new layout will connect with existing rooms. A well-planned layout should enhance your home’s flow while minimising awkward corners or dead spaces – although a top tip from Athina is to factor these nooks in early in the process and use them to create bespoke storage. A win-win. She also advises to “think about furniture layout before finalising electrics: you don’t want to realise later that a pendant is in the wrong place!”

Even seemingly small decisions like where to position doors or how to arrange furniture can affect the room’s functionality. Take time to test different configurations on paper and imagine yourself using the space before committing to a final plan. Seek professional guidance if you can, as this will help you avoid costly mistakes and make the process more enjoyable,” says Wren.

Interior design tips for an extension

1. Start with a clear concept design

The place Wren always starts with her clients is creating a clear concept design to set a vision for the project, to make sure that nothing feels disjointed. “This includes the overall colour palette, mood, furniture styles and shapes,” she explains. “Each room will reference this, while still having its own personality.” The result? A property that feels cohesive and flows. 

2. Balance materials, colours and textures for cohesion

“A cohesive space is all about balancing materials, colours and textures across both the original home and the extension,” explains Athina. Her go-to ways to achieve this include keeping flooring between the old and new areas consistent for seamless flow, using repeated elements (like metal finishes, timber tones or lighting styles) to subtly tie spaces together, and choosing a harmonising colour palette. “This doesn’t mean everything has to match, but it should feel intentional,” she says. “Use the same tone of just a few select colours to keep it feeling balanced.”

3. Think carefully about the connections  

To ensure that your new extension feels like part of your old home, consider how it connects to the rest of the house. Athina looks to archways, sightlines and material continuity to achieve this. The same applies to the outdoor-indoor connection: “The design of your doors should be in alignment with the design of the interior and exterior of the home. For example, if you have a very traditional design, go for a more traditional style of door,” explains Wren.

4. Doors make a difference

The style of door you choose leading out to the garden can make a big impact, not just on looks but feeling too, so consider your indoor and outdoor space and how you want to use it. Wren explains that sliding doors are a great choice for homes with limited patio or garden space: “they allow you to have outdoor furniture closer to the door. If the doors swing or open out, you will need to keep this area clear for access.” Athina recommends the same, to balance views and functionality. 

Bifold doors and crittall-style doors are also popular choices, but again, it depends on what you want. Athina advises that bifold doors can be bulky when folded back but create a full indoor-outdoor feel while crittall designs frame the garden beautifully but don’t open quite as wide. 

5. Sometimes less is more

An insightful point from Wren is that if you’re weighing up extension types (side return or rear extension) it’s important to think about how the extra space will impact the useability of the room – she does this by reviewing the layouts. “For example, one of our clients was considering a 1.5 or 2m extension and we explored how both options would impact the interior and exterior layout. More space is not always better, you must consider how it will feel within the context of your home and take a balanced approach—weighing up your return on investment,” she tells us.

6. Balance natural and artificial light  

“Extensions can be darker due to their depth, so rooflights and bifold or crittall doors should be strategically placed,” Athina says. Her “go-to” formula is a combination of ambient lighting (soft ceiling downlights and pendants), task lighting (under-cabinet lighting in the kitchen or reading lights in the living room) and accent lighting (like a statement pendant or picture lights).  

Think about lightbulb colour, too. “For residential homes, never buy cold light bulbs, always warm lightbulbs. We also recommend having light fittings with a soft textured shade, like linen. They will provide a soft, relaxing glow,” explains Wren. Incorporating dimmer switches so you can adjust the light levels throughout the day and year, and tailor the light in the room to what you’re doing, is another top tip.

7. Don’t forget that UV can damage furniture and furnishings

It’s not just our skin that can suffer from the sun, our homes can too. If you have lots of direct natural light in your extension, Athina reminds her clients that rays can damage or bleach fabrics and wood, so it’s important for longevity to add UV protection onto upholstered furniture or onto the window glazing through UV film.  

If you’re buying new furniture, many ‘smart’ fabrics are now designed to be UV-resistant and limit the effects of sunlight, so double check this before you invest. 

8. Choose colours that make you feel good

“Colour is very personal,” Wren says. She factors in colours her clients are naturally drawn to, plus their personalities and location when helping to plan extension colour schemes – they might want something a bit brighter and more joyful to counteract London’s typically grey skies, for example. She always recommends to sample the paint before committing. by buying a sample pot. “Paint an A3 piece of watercolour paper, then pin it to the wall, and move it to different spots, to see how the colour looks in bright light and shadow.”

9. Consider the direction your extension faces 

“Consider your cardinal direction, too,” says Athina. “Natural light has a profound effect on how a paint colour will look in your space, and this varies significantly depending on the orientation of your room.” For example, north-facing rooms are naturally cooler and darker due to limited exposure to direct sunlight, so colours with warm undertones, like soft pinks, pale yellows, or rich creams, can counteract this. South-facing rooms on the other hand get warm light for most of the day, allowing for greater flexibility in colour choice – “just be aware that south-facing light has a yellow tint, which can intensify colours with yellow undertones,” she says.

10. Look to your ceilings to add grandeur and character

Athina notes that sometimes in terraced houses, even with an extension in place, the spaces can be quite narrow and long. So if you can, raising the ceiling height can counteract the narrowness and add an element of grandeur. You could look to make a feature of the ceiling too: “A pitched or panelled ceiling adds instant character to an extension,” she says.

For more expert interior design advice, follow the designers on Instagram or visit their websites to get bespoke help with your extension.

@topologyinteriors | topologyinteriors.com

@_be_kin | Be-kin.com

Find a home extension contractor with Thomas from The Page

Planning an extension doesn’t have to be overwhelming. At The Page, we specialise in matching homeowners with pre-vetted, hands-on Pagers (our contractors) who can bring visions to life at competitive prices – without sacrificing quality. We’ve already done the hard work of finding exceptional teams: we work with Pagers not just for their skills but their approach to project management and communication.

Thomas, our in-house renovation coach understands both the practical and emotional aspects of extending your home, providing expert guidance at every step. We’ll help you understand the process, connect you with the right Pagers and professionals for your extension, and ensure you feel confident and supported from start to finish.