Earth & Mineral
Earth and mineral materials are those drawn from the ground and used with little chemical transformation: soil, clay, sand, stone and lime, shaped into walls, floors and renders by compaction, firing or curing rather than synthesis.
This group of materials runs from the ancient and unprocessed – rammed earth, mudbrick, clay plaster, stone – to the fired and the burnt, where clay becomes brick and terracotta, and limestone becomes the lime that has bound masonry for millennia. Concrete sits at the far edge of the family, mineral in origin but carbon-heavy in the making – avoided here as much as possible. What holds across all of these materials is mass: they are dense, they store and release heat slowly, and they last in a way most of the built environment no longer does.
However, they do come with compromises. The unprocessed end – earth, clay, stone – is among the lowest-carbon building there is, but the fired and the manufactured end is not, and cement is one of the largest single sources of emissions on the planet.
Thermal mass is a compromise as much as a strength: it rewards the right climate and penalises the wrong one, holding cold as readily as heat where the design hasn’t accounted for it. And the unprocessed materials ask more of the people building them – rammed earth and mudbrick are labour-heavy, slow, and dependent on skills that are being lost over time, which is the quiet reason they stay niche.
Earth & Mineral materials
The strength of mineral-based materials is their permanence. An earth or stone wall built well outlives the people who build it, and a lime mortar can be taken apart and remade rather than demolished, which makes end-of-life a matter of reuse instead of waste. It’s a durability that comes with thermal mass: the same density that carries load also stores heat, steadying indoor temperature through the day in the climates that suit it.
Where this groups of materials really shines is in the fact that they’re low in processing – rammed earth and clay arrive with a fraction of the embodied carbon of those that are fired and heavily manufactured.
Low processing
Rammed Earth
Damp subsoil compacted in layers into solid, load-bearing walls, left raw as the finish. It's among the lowest-carbon walling there is and holds heat beautifully; it's labour-heavy, slow, and only as good as the mix and the climate it's built for.
Lime
Burnt limestone slaked for mortars, renders and washes, breathable and endlessly remakeable. It lets masonry be taken apart and reused and self-heals fine cracks; it's slower to set than cement and carries firing emissions, though far below it.
Related reading
The ultimate guide to lime and lime plasters
A reference guide to one of the oldest building materials, and its misunderstood revival.
The Apple House is an imaginative test of natural materials
A community building with heart, The Apple House features hemp, lime plaster, spruce glulam and an earthen floor – all with a respectful outlook to the surrounding orchard.
Casa Plaj is a study in lime render
At Casa Plaj, a holiday residence in Portugal, the defining feature is a lime render skin that coats the building inside and out.
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