To cross the threshold into Clare Cousins’ home is to immediately get to the heart and mind of this Melbourne architect. The extended Edwardian house takes all of her talents, priorities and penchants and simmers them down into a beautifully balanced building.

On a pretty tree-lined street in Melbourne’s Prahran, the frontage provides little hint of the adventurous design to come. But swing the door open and a halo of filtered light beckons the eye to discover the boundary-pushing extension and detached studio beyond.

The space Clare shares with husband Ben Pedersen and daughters Ginger, four, and Ivy, one, is nonconformist yet timeless, refined and family-centred. Clare and Ben, who is the director of Maben Group commercial construction company, snapped up the house five years ago and let the project brew for three years. At that point, the original front rooms were in good condition, but the early-90s back addition needed demolishing and rebuilding on the 510-square-metre block – relatively sprawling for such an inner-city postcode.

Visually, the style is set by the newly built garage and studio at the back. Inside, the studio is set up as a fourth bedroom with an ensuite for guests, but it may one day serve as a teenagers’ hangout, granny flat or home office. Its exterior screening gives a nod of acknowledgement to the famous glassware designs of Finnish master architect Alvar Aalto, with the curving timber slats filtering western sun and providing privacy from neighbours. And it brings a big hit of atmosphere to the house. “We were never going to have a lush green outlook and so we were keen for the studio to be quite sculptural,” says Clare.

It is in this spirit that Clare conceived the house extension. Instead of a linear floorplan, the layout dips into the garden and wraps around it. “There was a great opportunity to test, explore and push boundaries – to take a leap of faith,” says Clare. A curved glass wall extends the surface area of the house to let in torrents of northern light and build a greater connection to the garden. But despite this, the building remains relatively modest in scale. “The smaller we could make the house, the more outdoor space we could keep,” Clare explains.

As both client and architect, Clare was only confined by the context of the redesign. “The challenge was slipping spaces next to one another,” she says. “The house isn’t single-fronted or double-fronted; it’s in-between.” With a second living area behind the kitchen and a built-in study and bar enclosed by a sliding perforated metal screen, the nine-metre-wide floorplan is pushed to its limits. “It’s a luxury to have two living spaces in proximity to the kitchen – sitting rooms at the front of a house don’t get utilised. The second of these sitting areas is more enclosed, so the kids can leave toys out. And even though we call it a playroom, it is the spot where Ben and I gravitate to on cold nights,” she says.

The big ideas that frame the house manifest into the tiniest interior details. The fluidity of the building follows through all the way to the bathroom cabinetry and the Calacatta marble kitchen benchtop. Even the U-shaped bank of seating enfolds the lounge room in rounded shapes. “The beauty of curves,” says Clare, “is that they soften sharp and hard lines. That’s why we continued them through to the home’s detailing.” Clare called on family experts to help execute her vision. Ben’s company built the space, and her uncle, garden-design legend Rick Eckersley, helped with the landscaping.

The soaped-timber ceiling, glazed brick walls and exposed-aggregate concrete floors articulate the simplicity of the structural materials. Even the plasterboard is unpainted. “Honest is a word we use a lot. It’s about really celebrating materials in their natural state,” says Clare.

The architect has built her reputation on the authenticity and substance that underpins her work. “We try to make architectural gestures that are important and necessary. We won’t just do a curve as a fancy corner; it has to contribute to the experience of a space.” This approach has served Clare well. Her retail work for the likes of Aesop and Mimco has earned her a solid following. Here, in Clare’s own house, the philosophy that runs through her blood and her business finds a home on a more personal level. It also finds its match in Clare’s understated explanation of her refined choices: “This is just what we do!” she says.