Sept 30th, 2018: Cob House

[xoxoxoBruce]

Cob houses can be really cool because it’s basically mud and you can shape it like pottery.
Depending on who does the sculpting, carving, it can look like anything you want.
Mine would probably look like a third grader's art project, but I know monster could do a cool one.

Earth is probably still the world's commonest building material. The word cob comes from an old English root meaning a lump or rounded mass. Cob building uses hands and feet to form lumps of earth mixed with sand and straw, a sensory and aesthetic experience similar to sculpting with clay. Cob is easy to learn and inexpensive to build. Because there are no forms, ramming, cement or rectilinear bricks, cob lends itself to organic shapes: curved walls, arches and niches.

Earth homes are cool in summer, warm in winter. Cob's resistance to rain and cold makes it ideally suited to cold climates like the Pacific Northwest, and to desert conditions. Cob has been used for millennia even in the harsh climates of coastal Britain, at the latitude of the Aleutians.

Wait a minute, resistance to rain? I have a yard full of clay. Three drops of rain turns it to grease and with all the rain this year it could trap dinosaurs.

If you want to build with cob then you must test the quality of your clay. Cob also depends on the coarseness of the sand. This is how to do a snowball test. Combine your clay soil and sand in different proportions: 3:1, 2:1, 3:2, 1:1, 2:3, 1:2 and 1:3. For each, mix the sand and clay thoroughly and add just enough water to make the grains stick together when you squeeze a double handful very tightly.

Make compact balls of the mixes about 6cm (2.36 in) diameter. Then while holding a ball between thumb and index finger of one hand squeeze the ball with the thumb and index finger of the other hand at right angles to the first.

A ball made dry enough from the ideal mix should not distort by more than 0.5cm (0.2in) and be hard enough not to break. Then hold each ball 1m above soft ground e.g. a grass lawn, and drop the ball. If the ball breaks it is too dry or contains too much sand. If the ball deforms it contains too much clay or too much water. The ideal mix will maintain its shape on impact

When you have discovered the correct clay, sand and water mix use a tarp to mix large batches of clay and sand. Mix these dry in the tarp until you can't see patches of clay or sand then add water little by little treading and rolling the mix in the tarp. Once lumps are broken up begin to add the straw. Tread the straw in until it is covered with the clay/sand/water mix and then turn in the tarp. Repeat adding more straw and turn in the tarp from different corners making sure the centre is also turned. Continue adding straw until the mixture feels like a tough substance rather than a loose (squishy) mud. The cob in the tarp will now turn as a single mass. Adding more straw now is very difficult so this is when the mixture is ready

link

link