Architecture studio Cairn has used hand-poured hempcrete to form the rough textured walls at House Made by Many Hands, an extension of a Victorian home in east London.

Approached to redesign the "dark and cramped" home in Hackney, London and Edinburgh-based Cairn reconfigured and expanded its ground floor using a palette of low-carbon and bio-based materials.

This includes hempcrete – a bio-composite material made from hemp and lime – which has been used to form the extension's walls.

Meanwhile, its floor slab was created with LC3, a type of low-carbon cement made with limestone and calcined clay, which Cairn said is the first of its kind in the UK.

"We saw this project as a prototype for how a Victorian house might be renovated and extended with approaches that have a far lower environmental impact than the typical use of concrete, steel frame and plasterboard," founding director Kieran Hawkins told Dezeen.

As the client is a chef, the renovation centres around a large kitchen at the heart of the ground floor lit by a strip of skylights along one side.

To maximise the feeling of openness, almost all internal doors were removed, with both the existing brick pillars and new timber columns framing views from the entrance out to a small patio at the rear. It also benefits from higher ceilings, achieved by lowering the floor level.

Avoiding internal linings wherever possible, this kitchen is wrapped by an exposed hardwood timber frame infilled with hempcrete, which was hand-poured with the help of the clients.

"A wonderful consequence of the hempcrete specification was that the contractor, client and architects could all come together and cast it by hand as a communal activity," said Hawkins.

"The making was accessible to everybody as a way of building that used more human energy to use less fossil energy," he added.

On the first floor of House Made by Many Hands, Cairn renovated the home office and gave it access to a roof terrace at the back of the site.

Fixtures, fittings and furniture throughout the home are all reused from the existing home or reclaimed and sourced second-hand.

Other standout features of the interior include the kitchen counters, which are finished in wood with terrazzo tops, while the adjacent skylit bathroom is clad in pale pink tiles.

"Salvage yards and eBay became primary suppliers," said Hawkins. "The clients were determined not to use new items unless it was unavoidable," he explained.

"Items came with stories to tell and histories to imagine; the timber floor is reclaimed from Bow Magistrates Court, now laid below whirring mid-century Mediterranean ceiling fans."

House Made by Many Hands was one of 16 homes shortlisted in the 2024 Don't Move, Improve! competition, which was won by a family house with terracotta-coloured extensions by Emil Eve Architects.

Other recent projects constructed with hempcrete include a self-built studio in London by Commonbond Architects and a pair of guesthouses on a New York farm.

The photography is by James Retief.