A detailed cross-section incorporating your design updates.
This reinforced concrete beam (or bond beam) is poured along the top of all rammed earth walls. Its primary function is to tie the entire structure together, creating a rigid, continuous ring that distributes loads from the roof evenly. It prevents the walls from moving independently, providing crucial stability against lateral forces like wind or seismic activity.
Set into the wet concrete of the top sill, these bolts provide a secure connection point for a timber or steel top plate. The roof structure is then fastened to this plate, ensuring it is firmly anchored to the wall system.
The core of the wall, SRE is a mix of soil (sand, gravel, clay) and a stabilizing agent, typically 5-10% cement. This mixture is compacted in layers (lifts) inside formwork. The result is a dense, strong, monolithic wall with excellent thermal mass and a characteristic layered appearance.
Steel reinforcing bars are placed vertically within the wall, extending from the foundation up into the top sill. This reinforcement dramatically increases the wall's tensile strength, making it resistant to bending and shear forces, which is essential in seismic regions.
Often in the form of ladder or truss-style reinforcement, these steel elements are laid at regular vertical intervals between the rammed earth lifts. They provide additional tensile strength and help control shrinkage cracking as the wall cures.
Services are integrated directly into the wall. Conduits for wiring and sleeves for plumbing pipes are positioned inside the formwork before ramming begins. This avoids the need to chase channels into the finished wall, preserving its structural integrity and appearance.
A waterproof membrane placed between the concrete foundation and the rammed earth. The DPC is critical for preventing capillary action, where moisture from the ground could rise up into the earth wall, compromising its strength and durability.
The wall sits on a solid, reinforced concrete foundation and stem wall. This is poured monolithically to provide a stable base and raise the rammed earth at least 225mm (9 inches) above the finished ground level to protect it from rain splash and ground moisture.