London is filled with terraced Victorian homes undergoing straightforward updates to keep up with changing needs. But when Studio Ben Allen set out to refresh a home in a North London suburb, the property’s unconventional size and position paved the way for something special.

“This was an end-of-terrace home built next to a man-made waterway that has served London for over 400 years,” explains Ben Allen, practice founder and principal. “It had a much bigger garden and was probably a third wider than the other houses on the street.” Seizing this rare opportunity, Allen embarked on a similarly novel renovation, dubbed “The House Recast.”

Brightly coloured concrete beams and a louvred arch ceiling give the renovation its playful new personality.

Granted, the project began as just a modest extension to deal with the dark, cramped kitchen and a bathroom with a leaking roof. But Allen’s team soon ended up rebuilding a significant share of the house, introducing a new double-height space while also upgrading the electrical, plumbing, flooring and most of the windows. To futureproof the home for its owners, it also added an accessible bathroom on the ground floor.

The curved mezzanine balustrade coordinates with the scalloped patterns added to the building’s facade.

Then the real fun began. Encouraged by the clients, a retired couple, to embrace experimentation, Allen and his colleague Omar Ghazal leveraged off-site fabrication to make substantial use of concrete for both structural and aesthetic purposes. This approach emulates Victorian brickwork, which (despite its primary load-bearing function) was often richly adorned too.

“As a practice, we’re always interested in what’s holding the building up,” Allen says. “We thought it would be interesting if these structural elements were also decorative and visible from the outside.”

The addition’s structural beams extend to the home’s exterior, where they are decorated with a scalloped finish.

The concrete, which was cast off-site in Cornwall, is patterned and pigmented, with pastel green and red-orange used inside and on the rear elevation. Here, the extension’s green beams and columns transition into exterior finishes embellished with an attractive scalloped embossment. Combined with the red-orange panels on the second storey, the effect is architectural, geometric and playful. “It ended up becoming an essay in concrete,” says Allen.

Brass finishes accent the green upstairs bathroom, now joined by another, accessible washroom below.

That said, the house looks and feels anything but heavy inside. By creating a ceiling of semicircular arches (made from moisture-resistant MDF and painted the same colour as the walls) below a strip of rooftop glazing in the kitchen, the architects separated views and light. “It’s about trying to keep a sort of clarity so that when you come into a space, the main focus is the view out to nature,” explains Allen. “But then you also bring in light from above to make sure the new space is bright enough.” The louvred ceilings in the kitchen and bathroom also contribute to dazzling light effects. “When it’s bright sunshine, you get quite strong shadows,” Allen says, “but a lot of the year, the skies here are quite grey, so you get a softer, more diffuse light.”

A hatch connects the kitchen and living room to facilitate easy conversations and cocktail hour drink transfers.

Internal views and connection points in the home were created using hatches installed in strategic locations (there’s one between the study and mezzanine-level book nook that lets you sit at the desk and look down into the kitchen and garden) and an intriguing use of arches. “We tried to create these fun alignments between the vaulted space above the kitchen, the arch window on the back of the house and an arch we created that allows you to see into the dining room from the kitchen,” says Allen. This particular arch, as well as the kitchen’s new double-height wall and ceiling, have been covered in an off-white lime plaster that gives it a textural, almost plastic sheen. Combined with the deep blue of the staircase balustrade and the red-orange concrete steps that lead up into the dining room, the effect is akin to stepping into a surrealist painting.

An arched opening introduces a visual link between the kitchen and the raised dining room in front of it.

Despite the challenges of bringing cast concrete into an existing house and working with a large company that had to prioritize bigger contracts (there are surprisingly few companies doing interior concrete, notes Allen), the architect would do it all again in a heartbeat. “An interesting challenge could be to tweak the colours a bit more,” he says. “And it would be fun to do something freestanding in concrete — to take it to the next level. Maybe that’s the next project.” It could well be. Watch this space.