Nordic and Japanese traditions influence Edwardian house extension

Can you describe the project?

Harpenden House is the complete renovation of a large Edwardian property, with side and rear extensions, to create a flexible family home.

The house had been operating as a nursery for many years and felt very worn and institutional, but our clients had fallen in love with the generous rooms, large garden and peaceful street.

To transform the property into a contemporary family home, the brief included creating new kitchen, dining and living spaces with a separate but connected playroom, adding space for guests, and making room for hobbies including crafts, cycling and home brewing.

We added three angled volumes to the rear with a continuous undulating sawtooth roof, which offers distinct but flowing spaces. Large sloped rooflights illuminate the interiors with a calm, even quality which recreates the essence of Nordic light. A dramatic double-height space at the heart of the house establishes connections up and through the building.

Were there any significant factors that influenced the design?

The house is in a conservation area so we worked closely with the local planning department while developing the design. The two-storey side extension is more in keeping with the materials of the existing house as it is very visible from the street. Subtle contemporary detailing establishes this as a modern addition.

The building itself was in good condition structurally, so the construction work focused on the new extensions. We removed a poorly insulated conservatory and an external metal staircase which wouldn’t have been safe for the family’s young children.

How did you treat the building exterior?

The staggered form of the rear extension reads as a cluster of complementary volumes, which breaks down the overall scale across the wide house. While they appear almost as separate from the outside, there is a sense of continuous flow inside, with mono-pitched roofs orientated to the path of the sun.

Splitting up the new volume in this way allows a large amount of space to be added without dominating the original building and avoids the sometimes cavernous feeling of a full-width ‘box’ extension.

The natural variation of handmade waterstruck bricks provides a contemporary contrast while still complementing the existing brick. The side extension has a more traditional form with bricks chosen to match the original so it blends quite seamlessly.

How did you design the interiors?

The ground-floor spaces are interconnected but can also be separated when needed, allowing for different amounts of openness – throughout the day or across the years, as children grow older and want more private space.

A circular route ties together a relatively large footprint, while sliding doors act as partitions -– partly inspired by the owners’ love of Japanese design. The kitchen, dining and living spaces each have their own connections to the garden – including a sheltered patio where two rooms with large sliding glass doors meet.

Expansive sloped rooflights illuminate the new spaces with gentle, seamless natural light which washes through the interior, diffused by the roof shape and further softened by the lime plaster walls.

Natural materials have been used throughout but with the crisp detailing found in Nordic design – a nod to one of the owners’ Norwegian heritage.

What was the project’s approach to sustainability?

Alongside introducing an efficient new central heating system, we upgraded the building’s thermal performance with improved insulation, energy-efficient underfloor heating and high-performance glazing. Breathable lime plaster was used internally, which regulates humidity and stores CO₂.

What was the main challenge and how did you overcome it?

The ground floor is quite large so we had to think carefully about how to arrange it. It needed to work for family life and have different areas for different activities but also a sense of connection between the spaces. Using large sliding doors as partitions added flexibility in terms of how spaces were divided and allowed us to balance openness with intimacy.

What is your favourite moment in the project?

The window seat is a beautiful spot. It opens onto a raised planted bed so you have a real sense of connection to the garden, but it can also double up as a dining bench for larger gatherings.

Are there lessons from this project that might be applied elsewhere?

The project demonstrates the potential of imaginative high-quality contemporary design to work harmoniously with historic architecture. By conceiving the side and rear additions as two distinct volumes – one more in keeping with the existing building and the other clearly contemporary – we were able to satisfy the conservation area’s onerous planning requirements.

Also, by removing a significant area of existing floorspace at first-floor level, we could create the double-height space at the centre of the house – prioritising natural light and opportunities for unexpected connections and interactions above floorspace.

Emma Perkin is director and co-founder of Emil Eve Architects

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Key data:
Total contract cost £625,000
Area of extension 118m²
GIFA cost per m²  £2,500