External rendering is the application of a protective coat to the external walls of a building. Most buildings are built from concrete, brick or stone walls, and these are surfaces that are porous, and vulnerable at the joints of brick and stone. These, then become a point of entry for dampness that can then get into the building and damage your interiors and other furniture and other things inside it. External rendering will help to prevent all this by providing an impervious coating to the external walls.
Exterior wall rendering is essentially meant for the protection of the outer walls of a property or home. It should be durable and be able to resist the weather elements. This rendering can also help to increase the strength of the wall and create a surface that can take other external finishes like paint or other material, that can greatly improve the aesthetics of the building. In earlier days, even mud houses were given such protection by applying mud plaster mixed with certain material that gave some waterproofing property to the plaster. In modern times, most rendering is carried out with a mixture of cement and sand. Lime may be added. It is customary to add plasticizers to these mixtures that allow the render to become workable, and also some chemicals that give it a waterproofing property. Once the render is applied and it has dried out and gained its strength after curing, you can paint the walls to improve their aesthetics.
Some exterior wall rendering uses colors in the cement that then can then be left unpainted. All external wall rendering is meant to make the walls waterproof and prevent moisture from getting through. It also improves the appearance of walls, by presenting a uniform appearance and hiding all the joints. The thickness of the render on exterior walls is often determined by the weather conditions and even the state of the unfinished wall. Walls need to be cleaned and made rough to enable the render to hold on to the surface. At times, this is ensured, by nailing or fixing wire mesh to the walls, on which the rendered material can grip. Most rendering is done in two or three coats, with all the surfaces, left rough, except the final coat of render. Render can even be given different textures dependent on the architectural concept of the finished building.
Many modern-day buildings use other materials like stone, aluminum or other metals to provide the external render to walls of buildings.