Nowadays, rendering houses is a standard practice worldwide. Most people know that a proper render has an aesthetic function, beautifies the building, protects the walls against weather conditions, and keeps the building warm.
There are several types of house renders. Firstly, we can divide into the thick and thin coat renders. Thick-coat renders are used with 15-20 mm thickness. The traditional render is made by mixing:
sand, cement, lime, and water – cement-lime renders are characterized by high durability and vapor-permeability. Unfortunately, they have low elasticity, so they are very susceptible to cracking
sand, cement, and water – in the case of cement-lime renders, we can count on slightly higher water resistance but equally poor elasticity. In addition, these renders are set very quickly, which makes them very difficult to apply render.
Modern thin-coat renders are applied on about 1-3 mm thick. The variety of colours and application forms makes it possible, in the case of thin coats, to achieve the desired appearance of the building.
Thin-coat renders can be divided into four main types: mineral, silicone, silicate, acrylic, and insulated.
These silicone resin renders are considered one of the best ones because they are characterized by high elasticity, perfect permeability, resistance to water and dirt. They ensure a beautiful appearance for years, without the need for frequent renovations.
Silicone plasters are also highly resistant to overgrowth and the development of microorganisms. A wide choice of rendering a house also speaks in favor of this type of render coat.
The binding agent for these renders is cement. Low flexibility and resistance to water is compensated by high permeability and low price. Mineral renders are ideal for walls insulated with mineral wool or polystyrene foam.
The binder here is an acrylic resin. This house rendering distinguishes from other plasters by very low vapor-permeability. They should therefore be applied to dry walls completely. They are also not suitable for mineral wool insulation. Acrylic renders are perfect for conditions of medium air pollution. They are slightly less resistant to dirt than silicone modern renders. However, elastic render finish coat gives them high resistance to damage.
In recent years, it has also been widespread talk about insulated render walls, which usually refers to an external wall insulation system consisting not only of coloured render but also of insulating material. The insulating material can be polystyrene, mineral wool, phenol K5, or wood fibres.
According to the Energy Savings Trust research, adding insulation to a brick existing render can reduce annual heating bills by up to £500. Still, as well as this, EWI systems will make a property warmer and tighter, and the choice of rendered extension’ colours and textures will significantly enhance its appearance.
Motivations for external rendering vary, and many people find it difficult to choose between appearance, properties, and price. So what is the best way to avoid regretting a wrong decision?
As we have already mentioned, there are several criteria. First, of course, it’s necessary to take into account the type of substrate used on the wall. You should also consider the technology of construction of structural walls, the material from which the building was built, and the way it was insulated.
You can successfully use different renders on three-layer walls, where the last one is made of bricks or hollow bricks. However, it is better to lay a pre-coloured render that meets these requirements on single-layer walls that have not been insulated and must have sufficient vapor permeability. A traditional mortar is usually used for walls made of hollow bricks and wood while applying render is the best for insulated two-layer walls.
There are many other reasons why some people choose one render over another. For example, buying products that use nanotechnology creates a micro-surface with a structure that allows the surface to be cleaned of dirt and dust by wind and rain.
In addition, for many people, the colour of the facade is an essential factor, as it is more sensible to select light colours in areas particularly exposed to the sun, which will not cause the walls to heat up excessively and consequently crack and fade. Still, others are interested in using plasters with decorative aggregate. Such walls gain in aesthetics, but their rough surface transfers stress more efficiently and are resistant to scratches and mechanical damage.
Selecting a new render is not everything. Its later use and self-cleaning are equally important. If we want the exterior walls to look aesthetic and fulfill their tasks as long as possible, we have to follow several rules.
No external wall covering would be one hundred percent resistant to all the damages that might occur.
One example is the issue of biological corrosion to which renders are exposed in our climate. To avoid such a problem, we can add an active biological preparation to renders, which prevents the growth of algae and fungi. Otherwise, we can prepare for ugly grey-green tarnishes on a new elevation after only several months. Not only does it look unsightly, but what is worse, it damages subsequent layers of the render applied.
The texture of the render is also essential. A smooth surface does not withstand stress very well and cracks quickly, and the rougher it is, the more difficult it is for scratches to appear. However, rough ones catch dirt more rapidly and are more difficult to remove. Experts also say that the colour fastness of a facade is mainly dependent on its brightness.
Lighter colours tend to last longer, while darker and more intense colours lose their original colour more quickly, primarily through lightning under the sun’s influence. This is because darker colours absorb a lot more heat than lighter ones, which accelerates fading and the appearance of thermal cracks.