Growing things, right? That’s what soil does. In fact, it does it whether you like it or not – life will spring from the smallest sliver of exposed dirt. It’s what dirt does best.
But it’s not all that dirt can do.
Soil also stores rainwater, soaking it into the ground gradually and preventing floods. On the way, it filters water and removes pollutants. Soil is a carbon sink, and stores massive amounts of carbon safely away in the ground.
There’s another major use for dirt: it’s one of the world’s most important building materials.
Earth is a very democratic material, the most natural of natural resources to turn to, and people have been building with it for thousands of years. Many of those buildings remain, some of them very grand indeed, so earth shouldn’t be considered a temporary or inferior material. 10% of UNESCO World Heritage sites incorporate earth buildings. Among them are the city of Shibam in Yemen, which has 16 storey apartment blocks that look like they belong in some alternative Manhattan, but were built 500 years ago. Mali can boast the Djinguereber Mosque, which was built in 1325.
Just because earth buildings are ancient doesn’t mean they’re an obsolete form of architecture. I’ve lived in houses made out of mud bricks. I went to primary school in a building made from mud bricks. I have made mud bricks myself, and helped to build things. It’s very common. It’s been estimated that half the world’s population lives and works in a building made from earth.
There are all sorts of forms of earth building. In Britain we used to build cob houses, which involves pressing mud into lumps and jamming them together into thick mud walls. Other places build in wattle and daub, plastering mud over a web of sticks. Rammed earth buildings are made by pressing mud down hard inside a wooden frame. And of course you can make mud bricks, either baking them or letting them dry in the sun.
Earth remains a sound choice for building today, and there are plenty of reasons why you would choose it for a sophisticated 21st century home. It’s completely natural, so it has a very low environmental impact, including carbon emissions – especially if it’s replacing cement. There’s no construction waste, because it just goes back into the ground. It’s breathable, so earth walls are great for air quality and moisture control. It has good thermal mass, and it’s also very cheap. Done well, it can look stunning, like this lovely home in Arizona.
Not all soil is suitable for building with, and it won’t be appropriate everywhere. But where it is, it’s a good choice.