Cob Dimensions/Calculations

Hi, Im new to the site and new to cob. We want to build a small cob playhouse type structure as our first project. CAn anyone tell me the basic calculations for foundation depth/width in relation to wall height/roof structure? The play house will be going up in an area approx 3m X 3m. We are keen to get this project off the ground so any starter info would be much appreciated!! Cheers in advance!

Hi Niall,

Welcome to Permies !!! !

There really is not a set formula for any cobb matrix and how it will hold up under vertical pressures of a wall or other building design. Each culture does have "rules of thumb," but they are specific to each clay type, and cobb mix characteristics. As you probably know from reading and researching, some of these structures can be as tall as 10 or more stories in height! These are masterful designs, from cultures that have been working with earth architecture for well over several thousand years.

Another point I would like to stress from a 'safety perspective,' seeing that this is your first structure, is don't just design and build with cobb alone. I have been "playing in mud," for over 40 years from traditional Pueblos and Celtic cobbs restoration, to Japanese styles and much inbetween...I do not condone or support even in my own work, "pure mud walls." Can it be? Yes, and has been for thousands of years, yet when (even for these cultures) there is any major tectonic or wind event, they have massive loss of life when the older structures fail. This does not happen in "cobb-timber" designs, or very rarely. When it does, it is often because someone (in there infinite wisdom) thought it would be a good idea to add concrete to the mix is some fashion...which it is not!

So, come up with a plan, make a sketch of some sort, post it here and you will have all kinds of "eyeballs" looking at it for you.

Again welcome,

j

Cheers Jay, Ill be in touch!