This paper reports on key findings from research directed at investigating adaptations that can be made to earthen masonry to improve their resistance to moisture damage. The focus will be on low cost earthen masonry buildings in the hot and humid Tanzanian coast. There are several examples of earthen masonry being used for load bearing purposes. However, many of these techniques cannot be applied universally. For example, tall buildings in parts of the Middle East work for the hot and dry climatic condition. The exaggerated thickness of the earth walls that gives the envelope the required thermal mass also enhances their load bearing capacity. This would not work in different climatic conditions, especially in the hot and humid regions of the world. In addition to the need for securing thermal comfort for the occupants, the earth based bricks have to be engineered to counter the effects of several other factors in the external environment that diminishes the structural strength of the resulting wall through deterioration. These include moisture, temperature and the presence of sulphates in the adjacent soil. Earthen masonry is more vulnerable to this form of deterioration. This paper identifies flaws in the brick production that affect the durability of the resulting walling element. The discussion also draws lessons from the Swahili buildings that have deteriorated less than the contemporary units.