With the vast variety of options available in the market, choosing an exterior plaster can be a confusing task. Which is the best plaster is a question that everyone asks themselves in such a situation. The answer, as usual, is not straightforward. Here are some of the most important properties of exterior plasters to consider when making a decision for purchase.
- Durability and Strength
The durability and strength of the plaster determine its lifespan. It's advisable for the plaster to be water-repellent so that raindrops don't linger on its surface but instead run off without causing damage. This property of plasters is called hydrophobicity, and it's essential to ensure that its indicators are high to protect the facade from adverse weather conditions.
- Elasticity
The more elastic the exterior plaster, the more resistant it is to movement and cracking.
- Vapor Permeability
This is the ability of the plaster to allow residual moisture within the wall to escape. Keep in mind that residual moisture is abundant in new construction and even when installing thermal insulation systems on existing buildings. Vapor-permeable plasters should be combined with "breathable" thermal insulation materials like mineral wool and EPS (polystyrene). From this perspective, it's good to choose exterior plasters with maximum vapor permeability.
- Maintenance and Resistance to Soiling
Make sure the exterior plaster you choose requires easy maintenance, meaning it can be cleaned easily, and ideally, it should be resistant to soiling. The tendency for some plasters to become green is due to their propensity to promote the growth of microorganisms like mold and mildew. Ensure that your chosen plaster will keep your facade clean.
- Color Range
Color choice is undeniably of aesthetic importance. However, the color's resistance over time and how long you can enjoy the initially selected color without it changing or fading from sunlight and rain is an essential criterion in choosing facade plaster.
- Price
Price, while not a technical parameter regarding the thermal insulation characteristics of materials, is a factor that concerns everyone. Our advice is to think long-term and assess whether the investment in good exterior plaster will pay off over time with easy and cost-effective maintenance and an appealing facade. The market offers many options with a good "price-quality" ratio without compromising on quality.
What Is Exterior Plaster?
Exterior (facade) plaster is a coating applied to the external walls of a building, providing a smooth finish and protecting the substrate from the impact of external factors. Plasters usually consist of a mixture of lime or cement, water, and other additives (such as sand). However, in this form, they are not very popular nowadays.
Among contemporary plasters, three main categories are the most popular: mineral, acrylic (polymer), and silicone.
Mineral Plasters
Mineral plasters are offered as a dry mixture with a cement base, with added polymers and calcium hydroxide in the composition, which needs to be mixed with water before application. One thing to keep in mind is that they usually require painting after application, which means a longer process. You might wonder why to choose mineral plaster for your facade, then, if you'll also have to paint it.
- Firstly, because the materials are more affordable.
- Secondly, mineral plaster dries faster than all other types, making it especially suitable for humid climates.
As we mentioned, after application, mineral plaster needs to be painted with silicate or silicone paint not only for a better aesthetic appearance but also to provide a long-lasting protective barrier against environmental influences. This plaster is highly water-absorbent, making it vulnerable to atmospheric effects, so a layer of paint is required to protect it from the rain.
Mineral plaster is "breathable," making it a great match for facade insulations with mineral wool and EPS (polystyrene). It's suitable for those parts of the facade not exposed to mechanical damage.
Usually, this type of plaster offers the most economical solution in terms of price.
Silicate Plasters
Silicate plasters are pre-colored ready-to-use plasters that can be applied directly after mixing. They are made from potassium hydroxide with synthetic resins, which contributes to the natural high resistance of silicate plasters against the development of algae, fungi, and other microorganisms.
These plasters belong to the mineral plaster group due to the properties given by the mixture of silicate and polymer binders. The chemical composition of silicate plasters makes them particularly suitable for mineral substrates (including silicate primers reinforced with insulation).
One of their characteristics is that they are "breathable" and highly vapor-permeable, allowing moisture to escape. However, it should be noted that during the application process, they are sensitive to atmospheric conditions. After application, they become highly functional and durable under various atmospheric conditions.
In terms of price, they offer a good "price-quality" balance.
Acrylic Plasters
In acrylic plaster, as the name suggests, the primary component is acrylic polymer. In this type of plaster, the binding agent is a dispersion of synthetic resins. They are produced as a ready-to-use colored paste that can be applied immediately after mixing.
The main advantage of acrylic plasters is the long-lasting color resistance, which remains vivid and well-pigmented without fading and without requiring repainting every ten years, as with other types of facade plasters. Elasticity of acrylic plasters is also a significant benefit, reducing the risk of cracks.
Unlike mineral plasters, acrylic plasters are hydrophobic, meaning they have low water absorption and are highly water-repellent. They are versatile and can be used in any area of the facade. Another advantage is that they are easy to clean and maintain.
One of their main disadvantages is the promotion of mold and mildew development if not adequately protected. It should be noted that acrylic facade plasters are not "breathable" products. The acrylic resins in their composition are responsible for the plaster's impermeability. Therefore, it is not suitable to apply them to "breathable" thermal insulation materials and substrates.
Nevertheless, their price is not the highest, so as long as they meet your needs, they offer a good balance of price and quality.
Silicone Plasters
Silicone plasters are facade plasters where the binding agent is mainly based on emulsions of silicone resins and polymer dispersion. They are produced as a ready-to-use colored paste that can be applied immediately after mixing.
Unlike acrylic plasters, silicone plasters are characterized by high vapor permeability and better hydrophobic properties, making their surface highly water-repellent. These properties give the plaster strength and high resistance, even under extreme atmospheric conditions. Additionally, their excellent flexibility makes them resistant to movements and prevents cracking.
In addition to the excellent protection they provide, another primary advantage of these plasters is their low tendency to soil. This is due to alkaline additives that prevent the formation of mold, mildew, and discoloration.
They can be applied on various surfaces, including insulation materials like mineral wool, EPS (polystyrene), and cement-based materials.
From a budget perspective, silicone plaster is more expensive than acrylic and mineral plasters, but it is relatively easy to apply, has a long lifespan, and is durable.
Plasters with Nano Particles
Plasters with nano particles are considered the latest generation of plasters that have become relevant with the introduction of nanotechnology in construction. As the name suggests, they contain nano particles, which are so tiny that they are invisible to the naked eye. For reference, one nanometer is equal to one billionth of a meter (1 nm = 10-9 m).
The main advantage here is extremely high resistance to soiling. Of all the facade plasters discussed so far, this one is essentially "self-cleaning." This property is possible thanks to the "nanoporous" structure of the plaster, which prevents environmental contaminants from adhering to the plaster's surface.
Using nano particles in the chemical composition of the plaster contributes to its ideally smooth surface and the "nanoporous" structure, which hinders the attachment of contaminants from the environment to the plaster's surface. Thanks to its self-cleaning ability, you can enjoy a naturally clean and beautiful facade.