Double-height extension in North London - Grand Designs mag
Zucchi extension by Paul Archer Design

Double-height extension links London townhouse to its garden

A chamfered Portland stone frame funnels light into this previously gloomy space

By Alice Westgate |

Architect Richard Gill of Paul Archer Design describes how a double-height extension links two floors of a north London townhouse to its garden using carefully considered materials.

Owners Benedict and Helen Zucchi, who have two teenage children, wanted better access to the garden and an extension with good thermal performance. They also wanted to turn the lower floor into somewhere to read and paint, as well as for guests to stay. Helen is a music tutor and Benedict, who is an architect, grew up in the four-bedroom house.

The property already had an upper ground-floor extension, supported on stilts, with steps down to the garden, but the lower ground floor was overshadowed and very gloomy.

double-height extension to a London townhouse with chamfered and mitred Portland stone frame

The Portland stone frame was designed and manufactured by Ethical Stone and installed by Chiltern Marble. Reclaimed brick planters create a terraced garden on the lower level. Photo: Jonathan Gooch

Tell us about the design

The new double-height extension steps out 2.5m from the back wall and is slightly narrower than the house so it doesn’t appear too overbearing. Its chamfered and mitred Portland stone frame funnels light into the interior.

On the upper level a strip of overhead glazing makes the extension appear to float away from the back wall, while a balcony made from galvanised steel grating lets light into the floor below. The steps down to the garden are made from the same metal grating and reclaimed brick, which in turn matches the planters.

a double-height extension brightens up the lower ground floor of this london townhouse

On the lower ground-floor a curved timber wall (right) hides a utility room and bike store. A fold-down bed and a sliding partition converts the space into a guest bedroom. Photo: Jonathan Gooch

Was the build challenging?

Yes, it was far more complex than it looks. We didn’t want beams running across the rooflight so we hid the horizontal supports lower down in the structure. And lots of work went into the junction between the stone, the door, the metal and the planters – that’s a lot of trades in just 1sqm of space.

It was an interesting dynamic and there was a high level of scrutiny and detailing, but Benedict and I ended up bouncing ideas off each other really well. Ultimately, I think this collaboration encouraged us both to take more of a risk with the design.

bright upper ground floor open-plan kitchen diner with rooflight and floor-to-ceiling windows

The two-storey, 144.7sqm extension and renovation project cost around £2,550 per sqm. The main contractor was Clearly Renovations. Photo: Jonathan Gooch

How has it turned out?

There is a nice balance as the extension is striking without being monolithic. Both floors are filled with light and it’s lovely to sit at the dining table with the doors open and the breeze coming through. The view from inside is of greenery all around.

modern kitchen extension with rooflight joining the extension to the original house

Richard remodelled and refurbished the upper ground-floor, adding beautiful joinery including a coffee-making area beside the dining table. Photo: Jonathan Gooch