How to Make an Interlocking Soil Stabilized Block Machine

Cut the two-by-four wood into four pieces. Make two of the pieces 12 inches long and cut two so they are 9 inches in length.

Nail the pieces together to form a frame by placing the 9-inch pieces between the 12-inch ones so the ends are flush.

Screw the metal corner pieces onto the wood frame to reinforce the corners.

Cut two pieces of the two-by-12 board to form the top and bottom of the mold. The bottom piece should measure 12 inches by 14 inches. Cut the top piece so it measures 8 7/8 inches by 10 7/8 inches. Check to make sure that the top piece can fit into and through the frame. The fit should be tight.

Screw swing clips onto the side of the frame 2 inches in from each corner. The clips should be set so they can be moved down to hold the bottom piece flush against the edge of the frame.

Cut one piece of chamfer strip the length of the inside of the frame and attach the chamfer to the bottom piece of wood using finishing nails. Make sure the chamfer strip on the bottom piece does not interfere with it fitting flush to the frame when held in place with the swing clips.

Use a router to create a channel in the top piece of wood that is 1/2 inch in depth and set 2 inches in from one of the longer sides.

Wax the inside of the frame and the top and bottom pieces of the mold on the side with the chamfer strip and channel. Allow the wax to dry and apply at least four more layers. The wax will prevent the clay and cement mix of the brick from sticking to the wood of the mold.

Attach the bottom piece of wood to the frame using the swing clips. Make sure the chamfer strip is inside the frame.

Fill the mold with the soil and cement mix. The ratio of the mix will depend on the geographic area the block will be used in and the clay content of the soil. Consult the local building authority for the required mix ratios to meet the building codes.

Set the top piece of wood, channel side down, so that it fits within the frame. Make sure the channel is on the opposite side of the frame from the chamfer strip on the bottom.

Attach four c-clamps to the frame to hold the top piece in place. Slowly turn the clamps to increase the pressure on the top piece of the mold, pushing it down into the frame.Turn the clamp screws in small increments, alternating between the clamps to keep the pressure even. When the top piece will move no further into the frame, stop and set the mold aside to cure. Curing time will depend on weather and the clay content of the soil.

Remove the c-clamps and push the swing clips off the bottom piece of the mold. Gently pry the brick from the mold. The brick will need to continue to cure for several days before use.