Construction of the Walls
Unlike some other forms of earth building construction methods, cob building does not require a frame to form the walls.
The walls should, however, be supported on some type of foundation, which should encompass the area of the ground floor to aid the laying of the floor. A damp-proof membrane should be stretched right across the whole area of the foundation.
A dwarf wall of about 12" X 24" is sometimes built on top of the foundation to keep the cob clear of the ground and avoid possible water seepage into the base of the wall, which we will incorporate into our cob house.
The materials of the cob are mixed with water to a doughy consistency, and a glob about a foot diameter is formed, then hand-tossed a few times, and then laid on top of the foundation damp-proof membrane. Another glob is added to the back of this to make the wall about 24" thick. This is continued for a couple of yards or so, then this layer of cob is leveled with a plastering float.
The wall does not have to be straight, it can be any shape you want, however, it is better to keep it level from the start using a builders spirit level which is about 36" long.
This process is continued right along the length of the wall, and by the time you reach the end, the first lot of mix applied should be ready for another layer of cob.
And so the wall progresses; but if you feel the previous layer is not ready to continue building on, you can start another wall, leaving apertures for the doors and windows.
Provided you smooth the cob layers and level them as you go, you can take your time with the process. Folks who have built their house with cob seem to find it a holistic experience, so enjoy!
On finishing the final top layer of each wall, steel screwed rods can be pushed down into the cob to a depth of about 24", leaving 6" protruding. This is to facilitate the fastening of the wall/roof plate.
The walls should now be left to thoroughly dry out. When dry they can given a good brushing using a wire brush to give an aesthetic finish, then a few coats of specialist earth building suspension applied to the outside surfaces of the walls as a damp proof measure.