Essential homes

“Material impregnated with cement is the key to this project to create durable, waterproof homes for refugees. Just add water”

A small, unusually shaped concrete dwelling is attracting attention at the 2023 Venice Biennale of Architecture – the result of a partnership between the Norman Foster Foundation and Holcim.

Designed primarily in response to the global refugee crisis, the Essential Homes project offers a sturdier, longer lasting alternative to the tents traditionally used as emergency or temporary accommodation.

“It is estimated that there are currently some 100 million displaced people in the world,” says Christophe Levy, scientific director of the Holcim Innovation Center near Lyon. “But whether as a result of geopolitics or natural disasters, their need for emergency shelter is often long term: years or even decades.

“So we worked with Sir Norman Foster to see if we could create inexpensive accommodation that was quick and easy to build, but which would also provide comfort, dignity, and last much longer than a simple tent.”

The key to the Essential Homes structure is CCX: a cement- impregnated material manufactured by UK-based firm Concrete Canvas. Supplied on a roll, the product can be placed over a frame, formwork or even inflatable shapes, and then simply sprayed with water to create a hard concrete shell.

“It is a brilliant product and I wish I could say Holcim had developed it,” says Levy. “It comprises geotextiles sandwiching a layer of high-density cementitious mix with a little sand. The magic in the design is the way in which absorbent polymers – like those used in baby diapers – retain water so that you do not have to be too careful when activating the concrete. Just hose it down and the polymers optimise the water-to- powder ratio, ensuring the concrete is always perfectly hydrated.”

The example home in Venice measures 9m x 6m and is 3.4m high. The structure comprises a steel frame supporting a permanent formwork of 600mm-thick corrugated cement board, curved into a catenary shape. Six 1.5m-wide strips of CCX were layered over this and sprayed with water to create a 103mm-thick outer shell.

One of the original and still the most popular uses of CCX is to line irrigation channels, Levy says, so it is ideal for making the temporary home waterproof.

The vertical ends of the structure, one of which is inset to create an entrance porch, are made from Holcim cement board, and the company also supplied a lower- carbon cement for the CCX. Around 20% of the cement content has been replaced with limestone.

Levy and his team are now thinking about how the design could be developed further. “It could easily be made longer. It is simple to cut doors and windows in the thin concrete. It could interconnect with other such structures. Maybe it could be made higher, with a mezzanine.

Already the whole structure can be recycled – but I think we could work towards making the frame removable so it can be reused. When you go inside this building, it is a really pleasant environment with good headroom, natural light and storage at each side. To create a small home like this, in just days, with unskilled labour and for around €20,000 – the potential, I believe, is very great.”

And as for CCX: “There is so much you can do with it. I recently visited the slums of Manila where many people live under rusting corrugated steel sheets. They leak and are very noisy in the rain, and they become unbearably hot in the sun. A layer of CCX could be an inexpensive way of helping with all three problems.”

^{Words by Tony Whitehead}

Photos Chiara Becattini, Mike Cartier

^{Published in CQ Autumn 2023}