The authors have been developing low-rise reinforced concrete masonry buildings with the wall thickness of 150mm, for the purpose of the increase of inner space of buildings, the decrease of building weight, and the usage of the standard building module of 300mm. In order to realize the buildings, compressive behaviors of fully grouted masonry prisms, using small-size concrete units with a strength of 40N/mm2 class and various grout materials with a strength more than 50N/mm2, were investigated. The used materials are concrete, mortar and non-shrink grouts with or without aggregate.