The suitability criteria for soils used in earth construction is investigated. Four soils collected from earth heritage buildings sites were studied. Cylindrical fibred and non-fibred specimen were produced using cob and adobe techniques. An experiment campaign was carried out to after drying and conditioning the specimen to study the implementation process effect, geotechnical properties and mineralogical composition influence on the hydromechanical and microstructural behavior of the specimens. The hydromechanical parameters like dry bulk density, unconfined compressive strength (UCS), Young's modulus (E) and suction of the specimen produced were studied. The pore volume and specific surface area were also determined using the BET technique. The collective impact of implementation process, geotechnical properties and mineralogical composition of the soils on the hydromechanical strength (UCS and Suction) and microstructure (pore volume, Specific surface area (SSA)) of laboratory produced cob and adobe specimens was studied. A statistical analysis was conducted using the principal component analysis to analyse the complexity of the interactions among the parameters. The analysis showed that aside the geotechnical properties of a soil, the implementation process and mineralogical composition of a soil also have high influence on the hydromechanical strength and microstructure of the earth specimen produced.