If you are in love with building with cob, adobe or other types of earth techniques, the earthen floor is just so tempting. However for most people that idea sounds scary. I always hear questions like: Is that not going to wash away if I spill water on it? Or Is it durable enough? Honestly we also hesitated on the idea of earthen floor for a while, because it is just hard to believe, that dirt can become so strong. But we are very happy we decided to go for it, because the outcome is truly spectacular.
Look up our Stone-cob house gallery HERE
Advantages of earthen floors:
- it’s made of only natural materials
- nice and soft in touch
- easy to clean
- it can be adjusted to any shape of the room
- easy to apply on concrete slabs, wood or gravel
- possible with the floor heating
There are negatives of that technique as well of course. It shouldn’t be used in the rooms with the purpose of being a garage or a storage – where heavy furniture might be moving around. That is because it will be simply not that hard as concrete. But most of the time we want the earthen floors in the living rooms and bedrooms, when we can enjoy their beauty anyway. It also can’t be exposed directly on the rain and outside elements, since it will potentially break down with constant water flow running on it. However with a solid oil treatment it is still possible to apply it in the bathrooms. The last minus of earthen floor can be the time of making it. It takes way longer for a cob to cure than for a concrete for example. Which means we should not step on it at least for the first 2 weeks from a moment we apply all the layers.
How to make an earthen floor – step by step guide
Regardless the climate where to floor is going to be, drainage is always essential. Gravel or small rocks can be used for that. We decided to use a leftovers after a ruin house demolition to simply get rid of the material and give it a good purpose.
This will stop any humidity coming up to your precious floor surface. Very simple and cheap task to do and safes a lot of trouble afterwords. However sometimes it really depends on the room condition. If the interior itself tends to hold a lot of humidity, it is actually advisable to not apply the vapor. Because the cob is a breathable material, it will allow the moisture to travel through it. Therefore problems like mold could be solved. If you are not sure about the humidity conditions of your building, it is good to consult with the builder, before you make that decision.
Earthen floor acts like a thermal mass. It will accumulate the heat over the day and release it slowly in the night. That is why floor heating will work very well with that material. But if we don’t insulate it properly, it will just stay really cold all the time and attract mold issues. There are plenty of natural insulation materials, that are great to use in your floor: cork, expended clay and pumice are the most common examples. The most common question on that topic is: How thick my insulation layer should be? The answer will be always different and depend on material itself, on the climate you live in and in general on thermic performances of your house.
Road base implementation is one of the best way to level up and compact your side, before you start applying the cob layer.
When the ground is prepared, it’s time to implement your cob mix. We could make entirely new blog about how to make a good cob, but here we will just keep it simple. Most of the resources are telling that best ratio of the sand and clay are 3:1. But that will not tell much, if somebody never worked with dirt. In my opinion the one and only way of learning that is practice.
Here is a great link into more details how to get your cob mix done:
Specifically for the earthen floor it is important to make your mix with very fine sand and remove any little stones or other elements. You want to have your floor as smooth as possible and every little stone will make this work very annoying. This is also the moment, when you can experiment with pigments, to find your desirable color – or keep it just like it is. The mix should be also relatively liquid, so it can be spread equal over the same level. Once you have it done, you will need to leave it for at least 2 weeks to cure, depending on the weather. If the air is dry, we recommend to sprinkle it with water from time to time. You can also gently close spontaneous cracks happening, while the mix gets dry.
OIL AND WAX
The last task to do is the treatment. Of course it’s possible to leave your floor without the oil, if you don’t mind it being dusty and the water is not an issue. In fact, it is the oil, that will make it so durable and water repellent. Linseed oil is the most popular in any work with cob and it does great job. Important tip to know is, that it will make your floor darker. So it’s great to remember that while you choose the color. We recommend 4 to 6 coats of oil and it can be applied one after another. One more optional material is bee wax, if you want to keep it extra shiny and water repellent. It make sense specially in the kitchens or close to the main entrance, when it needs to be cleaned often.
More resources worth checking out: