Eight years ago, the architect and interior designer, Olivia Crawford, moved to De Beauvoir with her sister, Caroline. The siblings grew up in a traditional country house in Kent before living in a succession of rentals in London. The 19th-century maisonette they bought gave them the opportunity to create a place with permanence. The pair lived in the two-storey apartment for four years, gradually discovering how best to share the space, before they decided to renovate. Olivia in particular spent her free time reimagining the layout to best suit her and her sister’s needs.

Eventually, they were able to add a contemporary, open-plan living area on the lower-ground floor and generous bedrooms on both levels, so that she and Caroline had breathing space. The project not only provided the sisters with a sanctuary, but gave Olivia the impetus she needed to launch her own practice, Crawford Design. Now, as the home comes to the market, Olivia talks us through the transformative process – and reveals why she cannot wait for 5.30am site visits to recommence when she embarks on her next personal project.

Olivia: “I was 26 when we bought this home, so being able to find a place that Caroline and I could grow with was really important for us. It was 2014 – the height of the property boom – and there were about 12 couples looking around at the same time. My first thought was that the proportions are really special: the width and the height of the rooms make the space feel incredibly grand. Also, the fact that it’s a maisonette meant that we could live together without feeling on top of each other. I’ve probably made longer decisions buying a pair of shoes than I did buying this place. It was just mad!

“When we moved in, I took weeks off work, sanded all the floorboards and painted the entire flat white. We then lived in it for four years before doing any further work. In hindsight, I think that was one of the best things we did, because it made us really understand how we lived in the space together and what our priorities were.

“A lot of architect says this, but designing your own home is the hardest thing to do. You have a million and one ideas and trying to rationalise them can be really difficult. I’m also used to working on very high-end residential projects and we just didn’t have the kind of budget that my clients did. However, it was a priority for us to try and achieve that same quality. Caroline helped here, because she’s a lawyer, so she’s very pragmatic.

“When we came to renovate, we reconfigured the place. The kitchen used to be at the front of the house on the lower-ground floor, which is now Caroline’s bedroom. Our current kitchen used to be our living room, which was broken up with enormous supporting poles. Instead, we installed a crank beam to support the stairs, which has massively improved circulation.

“We dug down to build the extension because I wanted to recreate the same ceiling height we have upstairs, while also creating a seamless transition to the garden. We’re in a conservation area, so we were restricted by the depth of the extension. But, as a result, we have this incredible, secluded outdoor space that is now completely connected to the living space.

“A second bathroom was a priority for us and, because the upstairs rooms are so generous, we have divided up the space to fit in a shower room with storage above. This is accessed via the guest bedroom, which doubles as an office and overlooks the garden. We call it the green room; it’s the only non-neutral room in the house.

“We stuck to a really simple palette. On the lower-ground floor, we added engineered-oak flooring; the kitchen cabinetry is bespoke with Carrera work surfaces. I love the charm of marble – as it’s a natural material, you can see the surface age beautifully over time. Apart from the green room, we’ve used the same warm white paint from Paint & Paper Library throughout – using high-end finishes like this makes such a difference, especially when it comes to reflecting natural light. We’re north-west facing here, so we get a gentle, diffused light all year round, which makes it a really calming space to be in.

“We’ve complemented the pared-back interiors with a combination of new and old pieces. The carpenter’s workbench in the living room, for instance, is covered in paint and saw marks, but it brings so much character to the space. When we first moved in, we couldn’t afford original art so most of it has been made by me: the canvases hanging behind the sofa was made from leftover paint sample pots and building material – anything I could get my hands on. I made the frames myself, too.

“As a designer, you rarely get the opportunity to create a place that illustrates your own style, so having a blank canvas like this was really exciting. My first clients came to my practice as a result of friends saying: ‘Have you been to the Crawfords’ house?’ And our neighbours commissioned me to design their extension once they’d seen ours too.

“I do think this neighbourhood is particularly special. Everyone in the local deli knows our names – it’s so friendly. In the evening, there’s the De Beauvoir Arms, which is really atmospheric. It gets great light and has a beautiful outdoor space. Northchurch Road itself is just a picture. It has a beautiful church at one end and it’s incredibly leafy. At the weekend, it can feel like living in the country.

“My best kind of weekend here would be quite chilled. I’ll walk down the canal to Broadway Market, pick up a sandwich and throw a picnic blanket down on London Fields before coming back to the house for drinks and a barbecue with friends.

“While I adore spending time in my bedroom with the window open, hearing the buzz of the street below, I think it’s the garden I will miss the most. I love looking out at the beautiful lime tree at the back of it. To me, it’s like peering at a piece of art. And equally, sitting at the back of the garden in the evening when the lights are on inside is an incredibly special view.

“My sister is moving south to Herne Hill, where she hopes to buy. In an ideal world, we’ll end up close to each other. I’d love to find a period property, with original character, good proportions and lots of potential. For me, it can be another maisonette or a warehouse – as long as it will allow the opportunity to be adventurous in the design intervention. Finding another project will be really exciting. I cannot wait to be on site again. Hanging out with contractors is one of my favourite parts of the job.”