Hidden in plain sight: a subterranean Camden infill house built across three back gardens

If passers-by notice this house, they’re likely to register it as a quirky little garden room — a small, simple building, wrapped in black timber, with a stepped roof where meadow plants wave in the breeze.

In fact, it’s a four-bedroom, three-bathroom house spread over two storeys and bookended by two lofty, light-washed spaces, the kitchen and sitting room, full of interesting angles and each opening on to its a leafy courtyard.

Once inside, it’s all too easy to forget that this is, for the most part, an underground house.

Urban infill — the process of developing unused or under-used parcels of land within already developed areas — essentially means building new houses in the most unlikely of places.

With the price of property in London out of reach of a great swathe of the capital’s inhabitants, it’s no surprise that many of us find ourselves noticing odd little places — a row of ramshackle garages or an awkward gap between houses — and fantasising about what could be built there.

Perhaps that’s why award-winning practice vPPR has carved out a niche, in carving out niches. “We’ve done around 15 urban infill projects, we enjoy the challenge of finding a clear, regular geometry within a strangely shaped site,” says project lead and vPPR co-founder Tatiana von Preussen.

It was at an open house for vPPR’s Ott’s Yard urban infill project that the architects were introduced to James Youngman, a doctor with an interest in this idea. He’d bought a students’ HMO house in Camden with a really long back garden.

“The students used the bit close to the house but not the rest of it. So he started a conversation with the owners of the two neighbouring gardens, between his land-locked one and a point of street access, asking if they’d sell him the back section of their gardens, if he could get planning permission,” says von Preussen.

The doctor, a family man with children in their 20s, hoped that some of his kids might live here, renting out other rooms to friends.

To secure the planning permission, vPPR was asked to design a building that would keep the many neighbours happy, while still creating a good-sized house.

Presented with a site that spanned the three gardens, forming an unsatisfyingly irregular shape — a rectangle with one corner snipped off — the architects promptly set about bringing order and logic to the plan.

“We explored lots different ways of making the space work. There were so many things to consider, like aligning the house with the walls of the surrounding properties and avoiding the roots of large neighbouring trees.”

The answer, of course, was to dig, but the deeper a house is sited, the gloomier things get. After numerous iterations, the architects found a winning design that seemed to balance all the conflicting demands beautifully and which, to their slight surprise “and the surprise of several planning consultants”, was waved through by Camden’s planning department.

Now, at the heart of this irregular plot, the house occupies a neat, diamond-shaped footprint that aligns with the streets on either side, bringing a sense of balance to this once scrappy plot.

The entrance is on the ground floor, via a rectilinear block from which stepped terraces of meadow-planted green roof fall away on both sides, giving the project its name, Stepped House.

Inside at street level there are two bedrooms — both en-suite — and a mezzanine overlooking the sitting room. This is where the wow factor kicks in, as steps descend through a vaulted triangular space where chunky zig-zagging timber beams support a birch ply ceiling.

“You come into the entrance hall where you see this huge space with all the light pouring in from above, it’s such a surprise,” says Von Preussen.

At lower-ground level, a bank of glass windows and doors opens on to a well-planted and sunny courtyard garden. The other two bedrooms and third bathroom are tucked away at the centre of the building, below the upstairs bedrooms, and a short corridor takes you past them and into the kitchen-dining room.

This is the counterpart of the living room; again light, lofty and triangular, and opening on to a second courtyard garden. Here the stepped form of the terracing echoes that of the roof and leads to a raised seating area that catches the sun.

There’s another mezzanine level in the kitchen, too, where two desks create a work-from-home area. “The triangular spaces aren’t tall enough to be two-storey so it’s not a waste to have these gorgeous, lofty volumes,” says Von Preussen.

Key to the success of this house is the amount of light here, despite the fact that the building is hemmed in by a new wraparound boundary wall and most of the rooms are effectively at a basement level.

There are roof lights, which provide vertical views, with sunlight filtered through the green leaves of the mature trees that vPPR carefully worked its design around, while there’s a generous allocation of windows looking out on to each courtyard garden, too.

Walls have been painted in shades of off-white and grey, while the material palette features blonde-toned plywood and glulam beams, floors of pale oak parquet upstairs and light grey concrete at the lower level, polished to a soft sheen to maximise the light.

In the courtyards, the concrete is used in a shuttered form, cast in the same timber that clads the house to imprint the concrete with the grain of the wood — a classic technique of brutalist architecture that creates a sense of flow through the whole space.

The exterior timber is charred-black Accoya wood. The charring is a traditional Japanese timber conservation technique, Shou Sugi Ban, that prevents decay while managing to look both striking and unobtrusive.

“It’s quite unassuming from the street, which worked from a planning point of view,” says Von Preussen. Greenery, inside and out, is a key element of the project that will play an even more important role as the plants mature over the coming years — the project was completed in summer 2022.

The green roof is just one of the eco-friendly elements here, along with an air source heat pump and solar panels. The building has excellent insulation and is well-sealed but protected from condensation by a mechanical ventilation system.

Materials like the glulam beams are as strong as steel but from a renewable source, while the concrete was made up using 70 per cent GGBS cement replacement (ground, granulated blast-furnace slag) to reduce the concrete’s embodied carbon.