You design modular floor plans with distinctive loadbearing structures. How do floor plan and construction influence each other?
We are focused on creating innovative, democratic living spaces with nonhierarchical floor plans, where rooms are equal in size, typically spanning three to four metres. These standardised dimensions allow for more sustainable construction and enable us to use a variety of materials. For instance, in our residential project on Ibiza, the three-metre spans allowed us to construct a five-storey building from earth, as the reduced span means each wall carries a lighter load, thus lessening structural demands. Often, the layout of the parking garage dictates the loadbearing grid, but new mobility solutions are rendering garages obsolete. With the rise of autonomous vehicles, cars will independently navigate the city and can be summoned via an app. Where regulations still require garages, we explore alternative uses for them in the future. However, on Ibiza, a parking garage wasn’t needed – instead, we designed a landscaped outdoor parking area that is now fully planted with trees.
The use of earth as a loadbearing material on Ibiza surprised me. Is it economically viable in Spain?
From an economic standpoint, unconventional materials are often initially more costly, but as demand increases, prices tend to decrease. We are currently collaborating with earth production companies to explore new applications, focusing on two primary methods for incorporating earth in construction. One method involves smaller earthen blocks, which are easy to handle due to their light weight. In Ibiza, we used 10 × 10 × 20 cm blocks, each weighing under four kilos. The other approach involves larger building elements that can be lifted by crane, which reduces labour needs and lowers costs. We are currently experimenting with these larger elements, typically sized at least 100 × 100 × 20 cm to accommodate crane lifting. While larger modules reduce manpower needs, smaller blocks are more adaptable and flexible.
Are both methods new developments?
Yes, these methods are not yet standardised. The concrete manufacturer adapted his machinery for earth by using moulds designed for 10 × 10 × 20 cm paving stones, which works, although it isn’t ideal. We see greater potential in moulded earth blocks compared to rammed earth, as they can more easily meet regulatory standards. These blocks offer various advantages, including loadbearing capacities two to three times higher than rammed earth. We can produce them offsite – for the Ibiza project, the earth blocks were made in Lleida. The vision of building with solely excavated earth remains elusive. While it might seem that all we need is clay and a small amount of lime, we often need to add cement to ensure adequate strength.
Wouldn’t it be cheaper and easier to use bricks?
Earthen blocks have a distinct advantage as a hygroscopic buffer: they absorb excess moisture and release it when the air becomes too dry, unlike conventional bricks, which lose this ability firing. Earthen blocks are easy to lay. On Ibiza, where the relative humidity often exceeds 80 % due to the proximity to the sea (compared to 50 – 60 % as the ideal comfort range), earth helps regulate both moisture and temperature. While wood can also moderate humidity, earth is even more effective. The difference is noticeable – earthen buildings feel cooler, especially in summer.
What other construction materials have you experimented with?
Each project is a research opportunity, and we select materials that best suit the context. In Cornellà, we used cross laminated timber and glulam, which were well suited to that project, while in Mallorca, we used brick and natural stone masonry. We approach materials with openness, constantly evolving our work. For the Ibiza project, we initially planned to use wooden ceilings. However, to avoid installing heating and cooling systems, we needed greater thermal inertia for optimal summer performance, leading us to choose concrete ceilings instead. While concrete has faced criticism, it has many advantages when used correctly. Wood can also be used poorly – often, there’s simply too much of it. A guiding principle in our practice is reduction: fewer layers, lighter weight, less complexity. In one project, we built a beautiful, fully prefabricated concrete structure, designing the ceiling slab in a sculptural form, similar to our approach on Ibiza, to minimise concrete usage. Sustainable building and emissions reduction depend more on how materials are used than on the materials themselves. By halving the amount of concrete used in the structural framework, we effectively doubled the project’s sustainability.
