How to Build a Cob Microhouse

Nail one 30-inch slat to the side surface of the very end of one of the 9-foot slats. Nail the slat's other end to the side surface of the very end of the other 9-foot slat to form a U-shape. Do not hang the door. Place it in the opening of the U-shape with its top against the 30-inch slat. Place another 30-inch slat against the bottom of the door. Nail it to the 9-foot slats. Remove the door.

Dig two holes with centers 30 inches deep and 30 inches apart. Leave at least some undisturbed land between them. Hang the plumb-bob from the center of the upper lateral slat. Place the door frame's two extended slats into the holes. Raise the door frame to make its longer slats parallel to the plumb-bob's line. Fill the holes with dirt until they are level to the ground. Tamp the ground firm and even.

Thoroughly mix one part clay to three parts sand, adding more for wetter clay. You should be able to form shapes from this mixture, but it should hold its shape against gravity. Add two parts of straw to stiffen the mixture further. Add one part of water to make it workable. The water ultimately will dry out of course. If you add too much water, simply leave it to air out until it reaches the desired consistency. The material mixture should contain about 15 to 25 percent clay, 75 to 85 percent sand and aggregate, plus straw and water.

Shape the mixture into spheres 6 to 8 inches in diameter. Set two equal lines of spheres on the ground from the sides of the door frame in wide and even waves. Stack further spheres on those spheres to build a wall, adding side rows of spheres as necessary to reinforce it. Pack the cob of each layer to stiffen the wall until you reach a height not quite half way up the door.

Nail one 30-inch slat to the side surface of the very end of one of the 7-foot slats. Nail the slat's other end to the side surface of the very end of the other 7-foot slat to form a U-shape. Do not hang the window. Place it in the opening of the U-shape with its top against the 30-inch slat. Place another 30-inch slat against the bottom of the window. Remove the window. Nail the free 30-inch slat to the 9-foot slats.

Make a line on the ground at a right angle to one end of the existing wall. Dig two holes with centers 30 inches deep and 30 inches apart, leaving undisturbed land between them. Hang the plumb-bob from the center of the upper lateral slat of the window frame. Place its two extended slats into the holes. Raise the frame to make the frame's longer slats parallel to the plumb-bob. Fill the holes with dirt until they are level to the ground. Tamp the ground firm.

Set two equal lines of spheres on the ground from the window frame's sides in wide and even waves to lay the foundation for the next wall. Stack further spheres on that set to raise the wall, adding side rows of spheres as necessary to reinforce it. Pack the cob of each layer to stiffen it until reaching a height not quite half way up the window

Set another wavering line of spheres, equal in length to the first one, at a right angle to the free end of the new wall; set a final wavering line of spheres between the two remaining free ends. Stack the spheres to a height equal to the existing walls. Add spheres to all the walls to reach the desired height. Lay a short, straight line of spheres from each curve in the wall. Place a shorter one from the wall on top of it. Hang the door and window. Leave the cob for five or more days to dry and harden. Apply your chosen roofing.