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The Stone Demonstrator
Open today | Empress Space, Earls Court, SW6 1TT

Today, Future Observatory – the Design Museum’s national research programme for the Green Transition – unveils the Stone Demonstrator, a boundary-pushing prototype at Empress Place, located on the Earls Court Development site. This public installation puts the use of pre-tensioned stone structures to the test, calling for more sustainable materials and building practices in the construction industry.

The open-air Stone Demonstrator stands at three storeys tall, measuring 6.5m x 6.5m, with the ground floor and adjoining park open to the public. It has been designed by architecture practice Groupwork with engineers Webb Yates and Arup. The Stone Demonstrator, funded by Future Observatory and the UKRI Arts and Humanities Research Council (AHRC), acts as both a 1:1 scale research tool and a call for the construction industry to hasten its efforts to transition to low-carbon materials.

Nearly 40% of global carbon emissions are created by the built environment, with 11% coming from the construction of new buildings. Natural stone is an extremely low-carbon material. The Stone Demonstrator is a prototype of an alternative way to build that reduces carbon emissions by approximately 70% compared to a reinforced concrete frame, and 90% compared to a steel frame.

With the government aiming to build 1.5 million homes, the construction sector urgently needs to explore low-carbon alternatives to steel and concrete. Apart from drastically lower carbon emissions, one of the advantages of the pre-tensioned stone frame is that it is prefabricated, requiring less construction time on site than traditional methods. The modular elements of the structure can also be dismantled and reused.

The Stone Demonstrator consists of stone blocks that are connected by steel tendons and compressed to create pre-tensioned beams and columns. The floorplates are a mix of pre-tensioned stone slabs, combined with timber joists and a roof of dowel-laminated timber (DLT). The structure has a self-supporting facade of stone bricks, which are at least 90% lower in carbon emissions than London’s vernacular of fired clay bricks.

The equivalent structure using a steel frame with a clay brick facade would emit around 40,000kg of carbon dioxide, while a frame made of reinforced concrete with a brick facade would emit 32,000 kg of CO2. By comparison the Stone Demonstrator, produces only 3,000kg of CO2 – around 92% lower than the steel or concrete.

Alongside the Stone Demonstrator prototype, Future Observatory has also funded engineers at University College London to develop a guide to designing stone structures. The design guide, led by Professor Wendel Sebastian at UCL, offers an invaluable tool for the construction industry to make stone structures easier to adopt, and is a key step towards a building code for stone.

The Stone Demonstrator is located at Empress Space within the Earls Court development site. Central London’s largest cleared development opportunity, the 40-acre Earls Court site will be transformed over the next 20 years into a neighbourhood of 4,000 homes, 2.5 million square feet of workspace, 12,000 jobs and cultural venues set within 20 acres of green and open space. With its close proximity to the Design Museum, the development site is an opportune location to engage the construction sector in the carbon-reducing potential of stone structures.

For the last four years Future Observatory, in partnership with the UKRI Arts and Humanities Research Council (AHRC), has funded more than 100 research projects pursuing more sustainable design. Future Observatory has showcased this research through several free displays in the museum, as well as the major landmark exhibition More than Human, which opened on 11 July 2025, aiming to set a new direction for design based on humanity’s collaboration with the living world.

Justin McGuirk, Director of Future Observatory says: “Future Observatory is committed to supporting research into low-carbon construction methods, and the Stone Demonstrator is an ambitious contribution to the field. It’s a building as a research tool, a 1:1 scale demonstrator of an ultra low-carbon structure for the sector to study. And the accompanying design guide being produced by UCL is another key step in the adoption of structural stone.”

Amin Taha, Founder and Chairman of GROUPWORK, says: “Intended to demonstrate a viable alternative to every day building methods but at a fraction of the embodied carbon, this structure brings together almost two decades of prototyping and testing by Webb Yates, The Stonemasonry Company, Ateliers Romeo and Arup. Its purpose is not to promote stone for sentimental reasons but as an ultra-low-carbon alternative to reinforced concrete and steel structures clad in fired clay bricks. At 90 per cent less embodied carbon as concrete and steel frames and fired clay bricks, it’s the ethical choice.”

Steve Webb, Board Director of Webb Yates, says: “Corporations behind fossil fuel era materials such as steel and concrete do not want their investments to be become obsolete, so they often promote the idea that these materials will one day be produced using green electricity and hydrogen. In order to address the sustainability challenges that face us we need to reduce the growth in the amount of energy we use – simply swapping oil for hydrogen does not improve energy frugality. The stone in this frame is produced with a fraction of the energy required to produce the alternative materials. Adopting stone as a staple building material would close coal mines and not require their replacement with green alternatives.”

Peter Runacres, Head of Urban Futures at Earls Court Development Company, says: “At the Earls Court Development Company, sustainability is a cornerstone of our vision. We’re proud to host the Stone Demonstrator – a striking prototype that embodies our commitment to sustainable urban development and sparks public dialogue about the future of building responsibly”

Professor Christopher Smith, Executive Chair of the UKRI Arts and Humanities Research Council says: “Through the Future Observatory, AHRC and the Design Museum are supporting innovative design research, imagining and bringing closer to a reality in which across the UK we can have homes that are affordable, comfortable and environmentally sustainable. We are quite literally building the future.”