Facade paint: How to find
In order to make the right choice in view of the large assortment, you should inform yourself extensively about the different types of paint and their effects.
You can read about the differences and how to recognize good quality products here.
Painting the facade of a house is an elaborate and expensive undertaking that should be tackled regularly. The best time for this is spring. Because after a cold and wet winter, cracks and flaking can often be seen on the old facade, which in the worst case can also damage the brickwork.
High demands are placed on facade paint. It should not only be decorative in the sense of an attractive facade design but also have protective properties in order to withstand the various weathering influences. In addition to good adhesion to the substrate, the paint should be permeable to water vapor and water-absorbent and have the ability to bridge cracks. Resistance to the growth of microorganisms such as algae and moss can also be an advantage.
Facade paints in comparison
- Acrylic paint
- Silicate paint
Silicate paint, a mineral paint, was invented at the end of the 19th century by the craftsman and researcher Adolf Wilhelm Keim. The aim was to be able to paint works of art similar to those in Italy. But the harsh weather destroyed the works of art after only a short time. Out of this hardship, mineral paint was invented, which looks like lime but is much more durable. As a binder, the paint contains potassium water glass, which makes the paint not only long lasting, but also very weather resistant. In addition, mineral paints are very permeable to water vapor, i.e. they are open to diffusion. Consequently, no condensation occurs and the substrate can “breathe”. In contrast to emulsion and glue paints, silicate paints form an indissoluble bond with the mineral substrate, also known as silicification. Silicate paints are therefore only suitable for substrates containing silicon – the paint will not adhere to wood or plastic. But beware: Silicate or mineral paint has an alkaline-etching effect. Therefore, always wear protective clothing when painting!
Tip: Due to its diffusion-open properties, silicate paint is particularly suitable for painting clinker, which is also a diffusion-open facade material.
- Dispersion paint
Dispersion paints are based on the chemical principle of dispersion. Here, two substances are mixed together that normally hardly dissolve in each other or combine with each other. In order to nevertheless achieve homogeneity, certain binding agents and solvents are added. In the case of dispersion paints, the pigments form a temporary bond with the solvents and binders. For exterior use, synthetic resin dispersion paint should be used. There, it has to fulfill certain properties. In general, emulsion paints are convincing due to their good environmental compatibility and ease of application: emulsion paint is non-toxic, non-corrosive, and hardly emits any harmful substances, provided it does not contain biocides. Indeed, occasionally these are added to prevent mold. In addition, this type of facade paint is comparatively cheap.
- Lime paint
In the past, lime paint was mainly used for painting farmhouses, stables, and barns. However, the paint is less suitable for modern, multi-layered facades – today it is almost only used for facade renovations. Nevertheless, the paint has advantages: due to its alkalinity, it has a disinfecting effect and is also very breathable. If you decide to use lime paint, however, you must bear in mind that the color is not very intense and is therefore mainly suitable for facades in pastel shades.
Tip: It is best to pre-paint your facade with lime milk because the paint dries best on moist lime plasters.
- Polymer resin paint
Polymer resin paint is not based on water but contains solvents that are bound by acrylic resins. The facade paint is therefore not suitable for lightweight and thermal insulation plasters that contain polystyrene. Anyone wishing to paint with polymer resin paint should have a mineral substrate available, such as brickwork or concrete. The advantage of this facade paint is that it adheres very strongly and solidifies the substrate. In addition, it does not contain water and therefore allows processing at low temperatures.
- Facade paint with lotus effect
In a facade paint with a lotus effect, a synthetic resin dispersion paint is enriched with nanoparticles. This creates an artificial roughening of the paint surface so that it resembles the leaves of the lotus plant. The idea behind this is to obtain a surface that is as dirt-repellent as possible. In practice, increased dirt inhibition can be demonstrated, but paints with the lotus effect are nevertheless primarily sensitive to grease and are therefore by no means suitable for houses in industrial areas where grease-containing fumes are produced.
What binders are there?
- Organically bound facade paints
Synthetic resin dispersion paints are among the organically bound paints. They usually contain a synthetic resin such as acrylic or acrylic-styrene polymer. This binder bonds to the substrate after evaporation of the water. Consequently, these paints are called acrylic, acrylate or styrene acrylic paint.
Also 100% pure acrylic belongs to the organically bound paints and convinces with more flexibility. In addition, it is more weather-resistant and therefore also of higher quality than other facade paints with acrylic.
Occasionally, acrylic paints are mixed with special additives to guarantee certain properties. Facade paints with the SIL label contain siloxanes and have improved water repellency and water vapor permeability. Facade paints that have algaecides and fungicides are optimal for preventing infestation by microorganisms such as algae and moss.
- Mineral-bound facade paints
Mineral paints, i.e. mineral-bound paints, are almost exclusively silicate paints. Potassium silicate is used as the binder. Occasionally, a small amount of a synthetic resin dispersion is added to improve the properties.
How can you recognize good quality products?
If you want a satisfactory result, you should definitely not spare any costs when it comes to facade paint. So while bargains from the hardware store can be tempting, as a rule the quality is by no means comparable to expensive products. You can recognize quality paint by its high binder content. The higher the binder content, the more durable the paint. Binders also allow for even application and have better coverage. With white wall paint, it is also advisable to pay attention to a high proportion of white pigments, known as titanium dioxide pigments. The higher the proportion of these pigments, the higher the whiteness and luminosity.
The hiding power and wet abrasion of emulsion paint can be divided into different classes. The following applies to opacity:
- Class 1: Opacity at least 99.5 %
- Class 2: Opacity at least 98.0 %
- Class 3: Opacity at least 95.0 %
- Class 4: Opacity below 95.0 %
In the case of wet abrasion, a distinction is made between five classes:
- Class 1: The coating does not rub off.
- Class 2: The coating is fire-resistant and does not stain. It is suitable for heavily used rooms.
- Class 3: The paint is resistant to washing.
- Class 4 and class 5: When wiping, a clear abrasion is visible. The paint is unsuitable for living rooms but perfect for basements or storage rooms.
Step by step: painting facades correctly
Step 1: Preparation of the substrate
Before you can get started painting your facade, the substrate must be checked. Remove any plant residues and dirt. It is best to wash the facade thoroughly once, the easiest way to do this work is with a high-pressure cleaner. After that, also scrape off all loose and flaking spots and efflorescence.
Step 2: Drying
If you find that sources of moisture are present, they should be drained before the facade paint is applied. You can refill the corresponding areas with sealant based on a pure acrylate.
Step 3: How absorbent is the substrate?
If you want to repaint an old, crumbling facade, you should check how absorbent the substrate still is before painting. To do this, simply spray some water onto the facade: If the water is absorbed directly, it is essential to prime the surface, otherwise, the paint will streak and the durability of the paint will decrease. A primer based on pure acrylate is also best suited for this purpose. However, be sure to let this dry overnight.
Step 4: Prepare the plaster base
If you are dealing with chipped plaster, you must first reseal the affected areas. It is essential to note here that freshly applied mineral plasters should only be painted over after four to six weeks. Synthetic resin and dispersion plasters must be allowed to cure for at least one week.
Step 5: Are the weather conditions right?
For the result to be satisfactory, the right weather conditions must also prevail. For example, it should be at least 50 ℉. In addition, painting must not be carried out in direct sunlight.
Step 6: Apply the primer
Once you have completed the preparation of the substrate, you can start applying the facade paint. Here we distinguish between the pre-paint and the final coat. For the undercoat, you can dilute the paint to about 10 percent with water. The only important thing is to mix it thoroughly. Then apply the paint preferably with a roller, for corners and edges it may be useful to work with a brush. When painting exterior facades, make sure that you only roll “wet-on-wet” to avoid streaks and lugs.
Step 7: Final coat
For the final coat, proceed in the same way as for the undercoat, but the facade paint should be applied undiluted or with a maximum of 5 percent water.