The present work investigates the hygro-mechanical performance of compacted earth as an alternative to conventional energy-intensive building materials. Earth bricks were manufactured by applying high compaction pressures up to 100 MPa (hyper-compaction) to increase the density of the earth and hence to obtain mechanical properties that are similar to those of traditional construction materials such as fired bricks, concrete blocks and stabilised earth. A wide campaign of laboratory tests was performed on samples made of different earth mixes that were hyper-compacted at their respective optimum water contents. Stiffness and strength were measured by unconfined and triaxial compression tests while vapour adsorption/desorption was assessed by measuring moisture buffering value (MBV). Durability to water erosion was also evaluated by performing suction, immersion and drip tests according to the norms DIN 18945 (2013) and NZS 4298 (1998), respectively. Results showed that hyper-compaction largely improved the mechanical performance of compacted earth but that a marked increase in ambient humidity could produce a considerable reduction of strength. Durability tests highlighted that the unstabilised compacted earth could not be employed for the construction of structures exposed to natural weathering. The experiments also demonstrated the dependency of strength, stiffness, moisture buffering capacity and water durability on particle grading. In particular, it was shown that a fine and well-graded earth mix exhibited higher levels of strength, stiffness, moisture buffering capacity and durability than a coarse and poorly-graded one. One important challenge lied in the improvement of the earth durability against water erosion by adopting novel stabilisation techniques, which led to the development of an original stabilisation method based on the utilisation of plant extracts. The method was consistent with the principles of Enzymatic Induced Calcite Precipitation (EICP), which utilises the action of the urease enzyme to catalyse the hydrolysis of urea. This reaction produces carbonate ions, which then react with the calcium ions dissolved in the pore water to produce the precipitation of calcium carbonate (i.e. calcite), thus binding the soil together. The novelty of the present work resides in the utilisation of crude plant-derived urease enzyme instead of pure reagent-grade products available from chemical suppliers, which reduces environmental and financial costs. In particular, the urease enzyme was obtained from a liquid soybeans extract, inside which the urea and calcium chloride were subsequently dissolved to induce the precipitation of calcite. Measurements of pH, electrical conductivity and precipitation ratio indicated that the optimum equimolar concentration of urea and calcium chloride (leading to the largest precipitation of calcite) was 2.5 mol/L. An experimental campaign was finally undertaken to implement the proposed bio-stabilisation method into the manufacture of compressed earth bricks. The most promising versions of the proposed bio-stabilisation method were also the object of further investigation to assess the hygro-mechanical behaviour of the stabilised earth by means of unconfined compression and moisture buffering value tests. The findings, although preliminary, suggested that a noticeable improvement of strength and water durability could be achieved by the proposed stabilisation protocol, in spite of the difficulty in replicating exactly quantitative results.