The primary structure is an earthbag dome with both an interior diameter and height measuring 11’. The dome follows the shape of an inverted catenary as a three dimensional representation of the arch action.

Earthbag construction uses stacked courses of polypropylene bags filled with a mix of earth, sand and binder (cement for bottom courses and lime for top courses). Two lines of barbed wire are laid out between each course to maximize interlocking between bags.

In order to save on material quantities, two sizes of bags are used: 20” wide bags at the bottom and 16” wide bags around the top of the dome. However, this gap in width is not apparent on the final structure as it is hidden with a thicker layer of exterior finishes.

The three openings (two windows, one door) in the dome all follow the geometrically-stable arch shape to avoid the presence of lintels in the dome. However, because the door opening is relatively large, a concrete door frame surrounded by two 5’ long earthbag buttresses is added to ensure the global stability of the structure.

The buttresses and the entrance of the building are covered by a ferrocement roof supported by the dome and timber posts landing on concrete upstands located in front of the buttresses.

The structure foundation consists of a circular trench filled with car tires filled with gravel. This foundation provides a solid footing for the dome while preventing any water infiltration via capillary action. The first course of earth bags laid on the tires extends below the doorway and the buttresses in order to alleviate the impact of the door opening on the dome stability.

The ground floor slab is a 4” thick concrete slab poured on the top of a 2” thick layer of gravel in order to avoid any contact between the concrete and ground water. The structure also presents an additional floor 8’ higher than the ground floor slab. This upper floor consists of wooden planks atop timber joists embedded in the dome. At this level, PVC pipes are inserted between bag courses to provide ventilation and light.

Dome exterior finishes are made of cob (earth + sand + straw) and eco-bricks (plastic bottles filled with trash). They are covered by shingles made out of plastic bottles and nailed to the earth bags. On the inside, a thin metal grillage (usually called “chicken wire”) is nailed to the bags and wrapped into a thin layer of mortar (cement + river sand) covered by a form coat (cement + lime + coarse sand) and a final coat (cement + lime + fine sharp sand).

Door buttresses finishes are similar to the dome interior finishes with the exception of the lime removed from the final coat as the buttresses are outside and may be subjected to rainwater.

The dome is surrounded by a non-structural cob buttress with a mortar finish on the top. This buttress slopes towards the front of the building, thus causing rainwater to fall along the dome and buttress slope to two locations on the front of the building where drain tiles are buried in the ground.