A geotechnical studies has been carried out on the typically weathered Kenny Hill sedimentary rock. The objectives are to determine the geotechnical properties related to wet tropical weathering. The mandatory classification by weathering grade was adopted to classify the interbedded rock mass which is mainly constitutes of sandstone and shale. The purposes are to characterize and classify the engineering properties, stiffness characteristics and behavior of weathered sandstones and shale and consequently their behaviour as a composite rock material. A series of rock material strength tests were carried out, i.e. a uniaxial compressive strength and point load strength. The empirical strength models were developed based on sandstone and shale experimental data. Thus the rock materials composite strength, elastic modulus and stiffness were mathematically modeled with respect to their respective weathering grades. Conclusively it was found that as a composite rock the strength models, modulus and stiffness were influenced by their state of weathering and deteriorated non-linearly.