Corten curves and contemporary flair transform this terraced house in London

Working with a client with industry knowledge might sound daunting to many architects. Not so for Edward Williams and Laura Carrara-Cagni, whose award-winning architecture studio builds on over 30 years of combined expertise. With a strong focus on sustainability, their portfolio ranges from a villa on Lake Como to the UK’s first major NHS Proton Beam Therapy Hospital.

In south London, the pair has transformed a large Edwardian terraced house into a sustainable contemporary living space, with a striking new bespoke extension replacing an old conservatory. Completed in summer 2025, the light, open and energy-efficient house completely fulfils the clients’ brief.

Enter the Corten-clad Gallery house extension

‘My day job is working alongside architects and engineers to guide large-scale projects to completion,’ explains the client, a senior building industry figure. ‘When my wife and I turned our attention to our own home, we wanted to commission something that would feel very special. We knew Cagni William’s work, and their reputation for inventive use of space, immaculate detailing and coherent use of materials. Plus the practice is a leader in sustainability.’

Carrara-Cagni relished the opportunity to work with such an enthusiastic and informed client and found the brief inspiring. ‘It helped us produce something quite different from a standard glass box or traditional conservatory,’ she says. ‘And the clients’ ambition to create an energy-efficient, climate-friendly house enabled us to embed sustainability from the start. The terraced houses may look similar from the street, but at the rear and inside this home is very special.’

A bold Corten steel and glass volume known as the Gallery, the new extension certainly makes a big impression, with curved glass corners; perfectly executed joinery by WG Studio; large pivot patio doors; a central column hiding a wood-burning stove; and a welded roof supporting a wildflower garden. But its unique shape presented some unexpected challenges.

In Europe, Corten is sold only in sheets, so the architects had to change the columns from circular to welded cross shapes. ‘The curved glass corners with tight radii are only made in one factory in Germany, so this added lead time to the programme,’ they explain. ‘The pivot patio doors were made bespoke from Corten frames to fit into the structure, together with other Corten elements, and the whole gallery was given a final oil coat to blend them all together.’

Between the Gallery and the original Edwardian terraced house is a large timber and expressed steel open space kitchen/dining room with a long wall in textured oak panelling unit running the whole width of one side and concealing plenty of storage space, kitchen appliances and services.

The dining nook is connected to the Gallery by an opening in the original back wall which creates an enclosing space for the dining table. Oak shutters can be left open to admire views into the new extension and garden beyond, or can be closed to create a cosy dining space.

‘The glazed pivot doors create a glide from the entrance to the garden through the kitchen/dining open space, but when we open the shutters the whole home is seamlessly connected with the garden, the garden comes in the home and the home in the garden. We love this,’ say the clients.

The project is underpinned by the highest standards in craftsmanship, but also by the search for sustainability. In 2025, the practice launched Cagni Williams Energy, a dedicated subsidiary with a mission to accelerate decarbonisation in the built environment, helping clients to meet ambitious sustainability goals.

Thanks to an air source heat pump in the garden, underfloor heating throughout the new ground floor, and augmented by ventilation to avoid overheating and condensation, the entire house is now heated by electricity only.

cagniwilliams.com