Cob is mortar made of clay, sand and soil … perhabps you would think of the litte cottages in central africa but believe me, the modern cob houses have nothing to do with them! Cob has become very popular in the United States and all over the world 🙂
The advantages of building with cob are clear: it is ecological, environmental friendly, cheap, the technique is simple and you can extend it very easily later on! But in my eyes the very best of it are the forms and curvatures of the structure that are possible. So this is what modern cob houses look like, I’m so into this!!
I’ve been to barcelona recently and I juste loved the architectural style of the avant-gardist Antonio Gaudi. These forms, these curvatures! And the fact that many of his structures imitate nature, just like the pillars in the Sagrada Familia that are shaped like trees with there crown of branches that support perfectly the load of the roof! Or the hyperbolic shaped openings that reflect the sunlight perfectly into the building.
I’m still renovating my old town house and I have to deal with the given structure, which doesn’t allow me many eccentricities. But in a couple of years who knows? Perhaps I will sell my house to buy a piece of land where I could build a little smurf house out of cob for me and my beloved?
The technique is quite simple. You first build up a foundation out of stones and put the cob walls on top of it. It is recommended for static and isolating manners to build walls with 40-60cm thickness. In addition I would recommend adding lime and straw to the mortar for a bettter stability.
Building with cob has also many advantages from a static point of view. The structures will be flexible enough to compensate eventuel movements of the ground and the walls will regulate the humidity in the house naturally. You will get a perfectly healthy home climate. The wood in your building can work freely and the walls will follow the wood movements perfectly without cracking! And due to the regulation of the humidity the wood can’t rotten…
As an engineer in statics I’m no fan of the super-stiff concrete homes that we mostly have in our days. No one needs a floor who can sustain 450kg/m² in his home, this is completely overdesigned! In engineering, and especially in .aerospace, we use materials and shapes that are adapted to the loads that have to be sustained, not more! If you build your home too stiff you may have cracks later because the structure isn’t able to eliminate internal stress that occur in a buildings life. Rememder, your won’t build the empire state building but just a house! In addition, if you want to modify your house afterwards, like adding a window, this will lead to massive work if the wall is build out of concrete. But with a cob house any extensions or modifications will be done quite easy, even after many years. In our days we don’t build for the generations to come. We need homes that can be easily adapted to our present needs and our lifestyle!
And these forms that are possible! Most of the times the cob walls are plastered with lime+sand. I love to work with lime! The plaster is so smooth and cremy, and you have 3 h to work it! Lime mortar is just so pleasant to handle and if you cover it later with lime paint you will get these super sleek and velvety walls you might know from your travels to Marocco or Santorini. I’ve made a special topic about working with lime, the technique and the different mixtures:
So enough texting, take a look at these pictures I found on pinterest!! Isn’t this lovely?
I’m so excited about this that I’ll build my raised bed out of cob! But that will be another topic 🙂