Green terrazzo is teamed with concrete and clay-toned plaster at Terzetto, a London flat extension that architecture studio ConForm Architects has modelled on bay windows.

Located in a conservation area in Hampstead, the sunken rear extension opens up the existing flat, ridding it of its low ceilings and dark interiors, while reorienting its living spaces towards the garden.

ConForm Architects' design is defined by its bold material palette, which marries green terrazzo, concrete and clay-coloured plaster and is used both inside and out.

Externally, these distinct materials have been combined to evoke the components of a bay window – which are a plinth, column and pediment. This gives rise to a geometric form that is angled away from the neighbouring homes, helping to minimise the visual impact on them.

Balancing the coldness of concrete plinths and terrazzo columns, the clay-toned plaster of the roof adds warmth to the home while referencing the red-brick architecture of the surrounding terrace.

"The plaster takes direct reference from the red brick above and the green terrazzo blending in with the green verdant garden setting," said ConForm.

"These finishes were all put together with precision," the studio continued. "The rougher clay surfaces against the flat terrazzo and concrete really add to the composition of the material palette."

Inside, Terzetto contains an open-plan kitchen and living room that opens to the outside, alongside two bedrooms and ample storage space.

Its updated floor plan is a flipped version of the original layout, with the living spaces brought to the rear and the bedrooms towards the front of the flat.

The bathroom and an en-suite have been positioned at the centre of the plan where it is darkest, ensuring the bedrooms and the living area look out onto the outdoors.

"The bedrooms were both at the rear of the property, with the kitchen-dining space at the front," ConForm Architects told Dezeen. "This created the awkward result of having to walk through the bedrooms to reach the garden."

The polished terrazzo columns that surround the main living space also jut into the neighbouring bedroom, where they frame a small nook for a desk.

A hidden sliding door in the living area can be used to create an additional guest bedroom or a private snug away from the dining space.

Surrounded by mature trees, hard landscaping in the rear garden is designed by ConForm Architects as a continuation of the concrete floor and geometric plinths featured in the extension.

Meanwhile, oak kitchen cabinetry, flooring, doors and window frames aim to add warmth to the home while helping to further the connection between the inside and out.

ConForm Architects carefully considered the positioning of windows throughout the home, with skylights and smaller glazed areas offering curated glimpses of the garden from the entrance.

Meanwhile, a large trapezoidal skylight in the extension allows the kitchen to be filled with natural light while maintaining privacy from neighbouring buildings. In the rear bedroom, a high-level window above the desk frames views out to the garden, thanks to the sunken position of the kitchen in the extension.

Green terrazzo also took centre stage in architect Tim Robinson's garden studio, where it was used to help blend the building into its surrounding tropical planting.

Elsewhere in London, Gundry & Ducker used white terrazzo throughout White Rabbit House, which is a colourful extension of a neo-Georgian house.

The photography is by James Reteif.