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.
Staining problems can be caused by a number of situations. Efflorescence, a white deposit on the concrete surface, occurs when moisture moves salts in the concrete to the surface where they are deposited when the water evaporates. Rust staining may be caused by lack of protection of exposed rebar during construction, by loose scraps of tie wire left in the forms, or by inadequate cover for bars and bar supports.
To ensure that they are meeting their responsibilities to provide attractive buildings, the architects and engineers should study local pollution, rainfall, and wind direction, then choose a surface suitable for the environment. Plan for water to flow easily from one zone or panel to the next and create a drainage path to the full height of the building. Be sure to specify a good-quality, dense concrete mix with appropriate aggregate color.