It doesn't have to be more expensive to produce good-looking concrete buildings than to produce bad ones. What is needed is care in studying the rainwater flow over the facades, with attention to details to direct the flow properly. Rainwater initially acts as a natural cleanser as it hits a building. But as it flows over a surface collecting dirt, it is likely to deposit this dirt on adjacent surfaces. Absorption, porosity, and texture of the concrete will affect how much this rainwater affects the surface. Both small and large architectural features, such as the the slope of an exposed architectural surface, also affect the flow of rainwater and its affect on the concrete surface.