COB HOUSES

Press, Volume LXX, Issue 21323, 16 November 1934, Page 16

COB HOUSES

BUILDING METHOD OF THE PIONEERS MIXING CLAY AND TUSSOCK ON THE SITE The way cob houses were built by early colonists was described yesterday by Mr F. W. Borrell, whose parents arrived in Canterbury in 1859, and who spent his boyhood in a cob house. A correspondent in "The Press" recently asked for detailed working instructions for the erection of such houses. After choosing the site of the house, preferably on clay ground, so that the material would be readily available, the first thing to do was to mark out the position of the walls, said Mr Borrell. About six feet from the wall the top spit of soil was removed from an area about 10 feet bv four feet wide. The clay in the hole so made was then loosened to a depth of the spade, thoroughly worked up, and flooded with water. A small portion of the black topsoil first removed was then added, and the whole mass thoroughly mixed together and worked into a soft mud by tramping. This was damD work for the early colonists, who had not the advantage of modern gum-boots. The whole success of the work depended on the clay being thoroughly broken down at this stage.

Use of Tussock Straw A layer of loose tussock for binding was then scattered on the space left between the hole and the wall. This space was necessary to work in. Then alternate layers of wet clay and loose tussock were placed one on top of the other until all the loosened clay was removed from the hole. The whole mass was then thoroughly mixed together with four-pronged or potato forks until a fairly tough mass of mixed clay and tussock straws was produced. After this the first stage of the actual building was begun. A layer of the mixture two feet high and the width of the wall desired was then laid round the ground plan, being roughly squared up with a spade. The mixture was lough enough to stand by itself without boxing, although the experience gained in building with concrete showed that boxing would be useful. However, the pioneers could not procure sufficient timber for boxing, and this was one of their main reasons for building in cob. Allowing' for Windows The first layer was allowed to dry befpre another was laid, and then a fresh mixing was made, and the process repeated. If a new layer was added before the preceding one was dry it was apt to cause bulges. Blocks of wood were built in to the sides of the windows and doors so that the frames could be nailed on later. After the walls were roughly built they were trimmed down to a smooth surface with a sharp spade. Mr Borrell had heard of the window and door apertures being cut out after the whole walls were built with a crosscut saw, but it was for each builder to decide which method was the most suitable. Leaving spaces for the doors and windows had the advantage of saving material.

The native tussock, or snow-grass if it was available, was the best binding material to use for mixing with the cob. said Mr Borrell. These had the advantage over wheat or oat straw of not rotting until long after the walls were dry. It was essential to allow plenty of time for the cob to dry at each stage of the building, or the walls would lose shape.