Building an earthbag dome is a sustainable and cost-effective way to create a sturdy shelter using compacted earth in polypropylene bags. This guide provides a detailed, step-by-step process to construct an earthbag dome, ensuring durability and safety.

Site Preparation

Before starting the construction of your earthbag dome, it’s crucial to prepare the site properly. Begin by clearing the area of any debris and leveling the ground. This ensures a solid base for your foundation. Next, install a perimeter trench for drainage. This trench should be dug around the perimeter of the dome’s base, approximately 12 inches wide and 18 inches deep. Fill this trench with gravel to create a barrier against water seepage and to ensure proper drainage.

Foundation

The foundation of your earthbag dome is critical for stability and longevity. Start by pouring a concrete base that is 12 inches wide and 18 inches deep. This foundation should be reinforced with gravel to enhance its strength and stability. The concrete mix should be poured evenly, ensuring there are no air pockets or uneven surfaces. Once the concrete has set, you can begin stacking your earthbags.

Earthbag Courses

Filling the poly bags with soil is the next step. Use bags that can hold between 100-120 pounds of soil. The soil should be moistened to about 15-20% moisture content to ensure it compacts well. Fill each bag with soil and tamp it tightly to remove any air pockets. Stack these bags in courses, ensuring each course is laid at a 45-degree angle to create the dome shape. Use a tamping tool to compact the soil inside each bag thoroughly. Each course should be staggered to interlock with the previous one, similar to how bricks are laid.

Structural Reinforcement

To ensure the stability of your earthbag dome, it’s essential to incorporate structural reinforcement. Use 1/4-inch rebar pins between the bags to tie them together. These pins should be inserted diagonally through the bags, connecting them securely. Additionally, add 4-inch diameter rebar in both vertical and horizontal layers. These rebar layers should be placed at regular intervals throughout the dome to provide additional strength and stability.

Door/Window Installation

When installing doors and windows in your earthbag dome, it’s important to frame the openings with 2×6 lumber. This lumber should be reinforced with rebar and concrete to ensure it can support the weight of the dome. The rebar should be placed in the corners and along the edges of the openings to provide extra strength. Once the frame is in place, you can install the door and window units. Ensure that the frames are securely anchored to the earthbags to prevent any movement or shifting.

Eyebrow Arch

Creating an eyebrow arch with 12-inch diameter tires is a unique and effective way to add a decorative element to your earthbag dome. Start by stacking the tires in a circular pattern, ensuring they are evenly spaced and aligned. Once the tires are in place, fill them with concrete to create a solid arch. This arch should be attached to the dome using rebar pins to ensure it is securely fastened. The arch not only adds aesthetic appeal but also provides additional structural support.

Plastering

After the dome is complete, it’s time to apply a plaster layer to protect the earthbags from the elements. Start with a 1/2-inch layer of clay-sand mix, using a ratio of 1:1:1 for clay, sand, and water. This layer acts as a base coat and helps to seal the earthbags. Once this layer is dry, apply a 1/4-inch layer of lime plaster. This layer provides waterproofing and enhances the aesthetic appeal of the dome. Ensure that both layers are applied evenly and that there are no gaps or cracks.

Roofing

The final step in constructing your earthbag dome is adding a roof. Start by adding a 12-inch thick layer of insulation, such as perlite, to the top of the dome. This layer helps to keep the interior of the dome warm in cold weather and cool in hot weather. Once the insulation is in place, add a 6-inch thick layer of concrete to create a cap. This cap should be sloped to allow water to run off and should be reinforced with rebar to ensure it can withstand the weight of the insulation and any additional elements.

Practical Tips

  • Use salvaged materials whenever possible to reduce costs and environmental impact.
  • Ensure that the soil used in the bags has the correct moisture content to prevent cracking.
  • Maintain proper alignment of the bags to ensure the dome’s shape remains consistent.
  • Reinforce corners with 4-inch rebar and concrete to provide extra strength.
  • Use a 2×4 corbel for the final course to support the roof.

Building an earthbag dome requires careful planning and execution. By following these steps and tips, you can create a durable and sustainable shelter that will serve you well for years to come.

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