Exterior walls are susceptible to atmospheric pollution, dust, dirt particles, and the growth of various organisms like mould, bacteria, moss, fungi, lichen, and algae. The UK often experiences an excess of rain, resulting in a significant deposition of organic matter on your walls.
Brick or masonry walls usually improve in appearance with age, so this doesn't always look bad on them. Nevertheless, a rendered surface is a sizable region with a single hue. The presence of algae and grime, especially on brightly colored render, detracts from the overall effect and looks unpleasant.
The challenge is that a wide range of renders are breathable, featuring a porous surface that permits moisture to evaporate, thereby creating a perfect habitat for the establishment of mold spores and organic growth. Getting rid of dirt and bacteria from textured surfaces can be challenging without special treatment.
The look of rendered surfaces can be seriously affected by graffiti, which is a problem in certain situations.
Furthermore, the accumulation of mineral salts, whether from winter road grit or sea spray, can harm render by crystallizing and causing small cracks or capillaries to form. This can lead to the formation of cracks, which usually need to be addressed.
The black staining on rendered facades is often a result of carbon and pollution. Green or red stains (particularly in coastal regions) are caused by algae growth, mould and bacteria that thrive on the surfaces, and that's when you need to take action.