Abstract: This study was aimed at investigating the factors responsible for the proliferation of biological growth on sandcrete walls and the effect of biological growth on walls. Two hundred randomly sampled buildings were examined for the presence of biological growths on their walls. Other characteristics such as walls texture, rendering/plastering status, painting status, age of building, nature of soil surface/cover amongst others were recorded in a log specially designed for this research. The approximate compressive strengths of the walls were determined in-situ using rebound hammer. Moss and algae collected from affected walls were subjected to elemental characterization using X-ray fluorescence test. Of the two hundred buildings investigated, 130 (65.3%) had one form of biological growth or the other. Most of the buildings affected by biological growths were between 10 and 20 years of age. About 88.6% of buildings unaffected by biological growths were rendered while 57% of those affected were not rendered. About 73% of affected walls had a rough surface thereby favouring the attachment of organisms. About 71% of buildings affected by biological growth were erected on unpaved soil thereby enhancing contact of walls with soil moisture. Majority of affected walls (63%) have compressive strength less than 10 Nm m–2. Moss and algae samples collected from walls were found to bear a striking elemental resemblance with cement which indicates that the major nutrients for the metabolic activities of these deteriorative species are obtained from cement paste in sandcrete and concrete matrix.