How to Build a Rammed Earth House

Rammed earth houses are one of the earliest forms of housing but houses built from more expensive materials have steadily replaced this type of housing over time. However, home owners are increasingly looking for cost effective ways to build environmentally friendly homes and a rammed earth house fit this description perfectly.

Materials

  • Low-grade brick-layering loam
  • Plywood
  • Shoot steel
  • Angle iron
  • Wooden planks
  • Building paper
  • Reinforcing rods
  • Rebar
  • Cement
  • Sand
  • Water
  • Rail ties (optional)
  • Baling wire

Tools

  • Hand-pounder or appropriately sized mechanical vibrator
  • Big hand saw
  • Drill with bolt-removing bit
  • Tape measure
  • Pencil and paper
  • Tarpaulin
  • Slanted screen of 1” mesh hardware cloth
  • Chalk line
  • Level

Building instructions

Preparing the earth

  • Find the correct blend of earth (50-75% sand without too much clay is ideal).
  • Sieve soil through a slanted screen of 1” mesh hardware cloth to separate out any big stones or roots.
  • Spread tarpaulin over the screened dirt to protect it from precipitation. Precipitation will cause the dirt to puddle, not compress. When you make a ball of earth in your hand it should hold its shape but break and scatter when dropped.

Foundation

  1. Lay out foundation using 2×6 planks lined with building paper and strengthened on the outside by 2×4 uprights, in 8 feet sections.
  2. Dovetail each section into the next and connect to it with reinforcing rods. Make forms 12 inches wide at the top tapering to 8 inches in the middle then out again to 12 inches at the bottom.
  3. Loop a chunk of baling wire around the uprights and snug the supports tight by twisting the doubled strand in its middle.
  4. Prepare foundation mix from 1 part cement, 2 part sand and 3 part gravel.
  5. After the first section of concrete is dry, move the plank forms forward so they overlap the previous pour by only a foot.
  6. Use a chalk line and level to keep the segments straight.
  7. Frame in door and window openings with 2×12 planks as you go along, being sure to brace them thoroughly.

Walls

  1. Line wooden moulds with shoot steel and edge with ¾” angle iron.
  2. Clamp wooden moulds onto the foundation and reinforce with 4×4 uprights.
  3. Use three pieces of 4×8 plywood to make an L-shaped form. The outside section sould measure 8×4 feet and the inside 7×3 feet. The mould should be 1 foot wide.
  4. Shovel a 4 inch layer of dirt into the form and pound the earth until it rings like rock.
  5. Keep on adding 4 inches and pounding.
  6. Cover your forms at night to protect the soil from rain and keep precipitation from the walls.
  7. Rammed earth hardens as it dries so the forms may be removed as they become full.
  8. Pull out bolts that hold the form in place and fill the holes that are left. This can be done by bending a piece of tin into a V shape, and holding the guide against one of the openings of the wall, filling the chute with dirt and pushing the soil into the hole with a bolt.
  9. Stagger the joints on your second course by placing a 1 foot long dummy unthreaded bolt crossways in the compacted dirt, about 18 inches from the end of the first form.
  10. When the frame is pounded full, remove the dummy and insert the first bolt for your next form in the resulting hole.
  11. Frame the window openings with 2×12 planks and ensure they are braced as you go along.
  12. Embed a 14 inch anchor bolt with a 3 inch washer every 3 feet along the top course of the earth. These bolts will hold a 2×12 plank which will serve as a footing for your roof (the cap).

Doors and Windows

  1. When a wall makes it to the top of a door opening, lay in a head piece such as a rail tie and keep on going. For the jams, drive a rebar into the wall and jam again.
  2. Do the same for windows.

Finishing up

  1. Libraries are stocked with books on how to make a roof, frame a window and do plumbing and wiring.
  2. Instead of wooden window sills, consider using concrete window sills with the outside lips slanted so water drips away from the earthen wall.
  3. Functionally, a rammed earth wall doesn’t need covering. However, for appearance the outside of the house can be painted with two coats of mortar made from 1 part cement and
  4. parts sand. Wet walls to prevent them from drying out too quickly and scratch finish the first layer.

Tips and Warnings

  • Building a rammed earth house is a time consuming process, however the more people involved the less time the work will take.
  • You will know when any two walls are exactly the same height by taping a glass tube to each end of a garden hose, and stringing the gauge from one wall to the other. When the hose is filled with water and the liquid’s level matched the top of both partitions, they’re level.