The Mud Home Guide to Earth Plaster
Natural clay or earth plaster is wonderful, but can be trickier than it looks.
Take a look at my in depth, online Earth Plaster Course if you're serious about natural renders.
How to Make Earthen (or Clay) Plaster
(Earthen plaster can be called clay plaster, because it's the clay that is the binding agent in the mix).
Earthen plaster is not simply a matter of getting your boots on and stomping about in a trough of clay. If you want it to look half way decent, it's a finely-honed skill. It took me just six weeks to get the structure of my earthbag house up in Turkey, but nearly two years on and off to perfect the plaster. But heck, who cares? Earthen plaster is the most satisfying, beautiful, tactile, cosy and inexpensive material I've ever used. If it's made correctly it's incredibly tough too. Cob, and wattle and daub homes that are hundreds of years old are still standing in the UK. I doubt Portland cement houses will ever be able to boast the same durability.
So how to make it?
Earthen plaster is not simply a matter of getting your boots on and stomping about in a trough of clay. If you want it to look half way decent, it's a finely-honed skill. It took me just six weeks to get the structure of my earthbag house up in Turkey, but nearly two years on and off to perfect the plaster. But heck, who cares? Earthen plaster is the most satisfying, beautiful, tactile, cosy and inexpensive material I've ever used. If it's made correctly it's incredibly tough too. Cob, and wattle and daub homes that are hundreds of years old are still standing in the UK. I doubt Portland cement houses will ever be able to boast the same durability.
So how to make it?
My latest mud creation: It's a skill that takes practice and know-how.
How to make earthen plaster?
You want a recipe don't you? You're going to be disappointed. I used to have a recipe on this page, but I’ve removed it because I genuinely think it’s misleading and a total waste of time to follow someone else’s recipe. I’ve made earth plaster in four different countries, and numerous regional locations and climates. Every time the mixture is different. Sometimes I've added extra ingredients, other times not. So get ready to experiment because both your climate and your soil are going to determine the quantities of each ingredient that you need.
You want a recipe don't you? You're going to be disappointed. I used to have a recipe on this page, but I’ve removed it because I genuinely think it’s misleading and a total waste of time to follow someone else’s recipe. I’ve made earth plaster in four different countries, and numerous regional locations and climates. Every time the mixture is different. Sometimes I've added extra ingredients, other times not. So get ready to experiment because both your climate and your soil are going to determine the quantities of each ingredient that you need.
A Rough Guide to Creating a Plaster Mix
1. Basic earth plaster is made by mixing clay, straw and sand together until they form a nice gooey stodge. It's much more satisfying, low impact (and inexpensive) to use your own dirt in the mixture. One way to test the amount clay in the mix is to do a soil test. You don't need pure clay to create lovely clay plaster (or cob). A fairly, loamy soil will do. Even
if you have no clay at all (which is pretty rare), you can still use your soil (see below).
2. Most soils are a mixture of clay, silt and sand. The very vague rule of thumb is one part clay, one part straw and one part sand. What this means is this: If your earth is very clayey, you will add straw (and possibly sand) to the mix. If your earth is sandy, you may need to add extra clay. Usually your there will be clayey areas, and not so clayey areas on your land, so hunt around!
1. Basic earth plaster is made by mixing clay, straw and sand together until they form a nice gooey stodge. It's much more satisfying, low impact (and inexpensive) to use your own dirt in the mixture. One way to test the amount clay in the mix is to do a soil test. You don't need pure clay to create lovely clay plaster (or cob). A fairly, loamy soil will do. Even
if you have no clay at all (which is pretty rare), you can still use your soil (see below).
2. Most soils are a mixture of clay, silt and sand. The very vague rule of thumb is one part clay, one part straw and one part sand. What this means is this: If your earth is very clayey, you will add straw (and possibly sand) to the mix. If your earth is sandy, you may need to add extra clay. Usually your there will be clayey areas, and not so clayey areas on your land, so hunt around!
The mud bath
3. For a nice smooth clay plaster, sieve your dirt before you use it. Then mix it with the straw and stomp it all together. It's much easier to do all this if your soil is dry first. Then you can sieve it, add the straw, mix it all up dry, and finally add water to bind it. After that, stomp away!
4. Let the earth and straw percolate for a few days. Then add the sand and any other ingredients you need (lime, brick dust, wheat paste, or manure). Make sure you mix it really well.
4. Let the earth and straw percolate for a few days. Then add the sand and any other ingredients you need (lime, brick dust, wheat paste, or manure). Make sure you mix it really well.
Percolated
5. Next apply it layer by layer.
Appying earthen plaster is therapeutic.
When you get it right, earthen plaster is incredibly rewarding. You can make sculptures, beautiful arches over your windows, shelving, wattle and daub structures, cob ovens, mosaics, and more. It gives your house a wonderful warm feel, without the horrible damp coldness of concrete.
Want to Learn How to Make Earthen Plaster?
Plaster is an art and a science, but one you can learn. For people who seriously want to learn the art of earthen plaster from base coats to finishing plasters, and create stuff like this:
"Very informative and good instructions in the text and videos! Absolutely helpful, thanks for putting it together." Nanda Doornik, cob oven builder in Ireland.
