Most concrete roofs are constructed using reinforced concrete which is known to have capillary tracts. Depending on the designed strength, density and installation techniques, the number of pores can vary. These pores are interconnected within the concrete and water will penetrate through such capillary tracts aided by osmotic effect. Concrete is known to be inherently weak in tension; cracks and voids can also form due to thermal expansion, contraction and shrinkage. As a result, water will seep through these voids.