Materials for Earthbag Construction

A: Earth/Dirt Material for Earthbag Construction:

Different materials have been successfully used for earthbag construction such as sand, dirt, crushed volcanic rock (scoria); etc. However, to pass the test that is needed for seismic design categories D, E and F, bags must be packed with different mixes of fluent, particulate material. These include earthen, cementations, manufactured and recycled materials that form into a permanent block. A good mix is approximately 70% sand and 30% clay.

A mechanical mixer is recommended if different material such as sand and clay need to be added together to get the right mix.

For more information about testing that has been done on earth bagwall and earthbag buildings, please visit:

• earthbagbuilding.com/testing
• earthbagbuilding.com/Testing/superadobe

B: Barbed Wire or Masonry Joint Reinforcement

To prevent the earthbags from sliding relative to each other in different course, barbed wire is always used between earthbag courses. Notes for Barbed Wire:

• Use the heavy 12 ½ gauge, four-point, is better than the 15 ½ gauge.
• Use two strands/lines of wire between courses/raws.
• At corners, use an L-shaped barbed wires or joint reinforcement to overlap with the barbed wires from each wall (as shown to the left), or use continuous wires. Overlap length should be at least two feet.

It is recommended that a testing program is developed for each project to test the quality of the soil/soil-mix used for earthbag construction. This is a particularly important if a building permit is needed in Seismic Design Category D, E, and F.

Similarities to Masonry Construction

Earthbag construction can be similar to masonry construction for the following reasons:

• Earthbag walls are placed on 6 to 8 inches lifts/courses/rows line masonry walls.
• Earthbag walls are built in running bonds, the same as masonry walls are.
• Low-rise masonry construction does not require high strength masonry units, the same as earthbags construction. In addition, earthbag walls are always thicker than masonry walls, so the stresses will be lower.
• Most designers who design Rammed Earth use the masonry design equation. Since earthbag is Flexible Form Rammed Earth (FFRE), masonry equations can be used for earthbag wall designs.
• Plaster/stucco is usually used on each side of earthbag walls.

This solves the issue of lack of shear strength of earthbag walls parallel to the wall. Also, it helps with bending moments due to loads perpendicular to the wall’s surface. In our practice at PSE Consulting Engineers, Inc., we use stucco on both sides/surfaces of the earthbag walls.

• The Building Code requires a minimum amount of reinforcement to be used for earthbag construction.
• A vertical bar every 4 feet on center that is required by the Building Code for masonry construction for Seismic Design Category D, E and F could be used for earthbag wall construction. The bar could be added within the stucco thickness, or through the earthbag wall itself.
• The Code requires a minimum amount of steel of 0.002 times the cross section of the wall. This amount could be provided for earthbag construction. The following amount/area of steel can be included in the Code minimum requirement amount of steel:
  • The steel mesh in the plaster/stucco on each side of the wall.
  • The steel bars in the bond beam at the top of the earthbag wall.
  • The steel bars in the top of the foundation/ bottom of the earthbag wall.
  • The barbed wire or the joint reinforcement used between the courses/rows of earthbags can be included in the required amount of steel.
• The earthbag walls can, and must be anchored to the roof or floor at their tops.