How to choose plaster for polystyrene foam for the facade

Making the correct choice of plaster for the polystyrene foam on your facade is crucial. Plaster has an impact on your exterior’s durability and insulating qualities in addition to how it looks. Your facade will look fantastic and withstand the weather well with the correct plaster.

This decision requires careful consideration of a number of factors. Make sure the plaster and polystyrene foam are compatible first. This compatibility guarantees longevity and appropriate adhesion. The local climate should also be taken into account as it may affect the plaster’s performance.

Examining a plaster’s characteristics, such as elasticity, breathability, and crack resistance, is also important when selecting the correct kind. These factors may affect the plaster’s performance over time, particularly in different weather scenarios. You can make an informed decision that will improve your facade’s look and functionality by keeping these important considerations in mind.

Why is it necessary to carry out finishing work on the outside of a building

The plastic polymer known as polystyrene foam has an odd structure—it contains micropores. It is installed on building facades to cut down on winter heat loss.

Because EPS and EPS boards are not robust enough, plaster is added as an additional layer of protection. They differ from one another. Therefore, compared to simple polystyrene foam or foam plastic, extruded polystyrene absorbs moisture less. However, it also absorbs up to 4% of the water when it comes into continuous contact with the boards’ structure.

This indicates that the plaster serves an additional function by shielding the thermal insulation from precipitation.

Furthermore, ultraviolet radiation has a negative impact on polystyrene foam. This initiates the material’s aging processes, which lead to their destruction. Natural erosion is the cause, and it speeds up in the sun. The exposed slabs will soon lose their thickness and stop serving their primary purpose.

It’s important to choose a plaster that offers strong adhesion, flexibility, and durability for polystyrene foam facades. The proper plaster will guarantee that the foam is adequately shielded from the weather and keeps its insulating qualities. To ensure a durable and efficient finish, look for solutions that have good resistance to moisture and cracking and make sure they work with foam materials.

Necessary tools for the facade under the plaster for extruded polystyrene foam

The preparation is just as important to the final product’s quality as the material’s characteristics and the degree to which the external surfaces of the supporting structures are finished according to technology.

• spatulas of different sizes (wide, narrow) with a smooth and serrated edge;
• a container for preparing plaster from a dry mixture and water;
• a hammer drill: thanks to the mixer attachment, you can prepare a mixture of a more uniform consistency without hard inclusions;
• a float;
• a needle roller;
• a brush or sprayer – used to treat the rough base with a primer;
• a building level;
• an electric drill – used to fasten polystyrene foam slabs;
• a sharp knife for cutting reinforcing mesh, polystyrene foam boards.

Sandpaper is required in order to grout the plaster layer. A unique grater is an additional choice. Sandpaper covers its working surface.

Types of plastering materials – which ones are better to choose

Examine the mixtures’ compositions before making a purchase.

• mineral;
• acrylic.

Because some of the current varieties contain ingredients that gradually degrade the foam, it is necessary to investigate the material’s properties. The compositions are compared based on the kind of active components when choosing what to plaster the exterior walls of the house with. Additionally, although in varying amounts, both choices include mineral additives. The properties of materials can also change as a result of the presence of auxiliary components.

Mineral

• cement;
• lime;
• mineral substances: sand, stone chips, due to which the structure of the material becomes granular.

The plaster in this category is long-lasting, with an average lifespan of ten years. Mineral compositions can be applied to polystyrene foam and foam plastic to finish it. The external layer can withstand variations in temperature, variations in air pressure, and exposure to precipitation. The adhesion of the plaster is low. Various techniques are employed to improve its adhesion to the polystyrene foam surface, including the use of reinforcing mesh, notches, and primer application.

The material’s low degree of elasticity is its primary drawback. Because the base and finishing materials have different rates of thermal expansion, the coating may crack after it has dried. Moreover, mineral-polymer plaster is available. It stands out for having a high degree of plasticity, which increases its resistance to deformation when heat expands. The coating’s service life is doubled.

Sand, slaked lime, and cement can be used to independently prepare mineral plaster. But there’s a chance that the ratios won’t be followed exactly, which will cause the adherence to the polystyrene foam to deteriorate. Assemble the primary parts. After mixing them, add water.

The risk of getting a material that is inappropriate for the structure is what poses a threat in this situation. For instance, if the consistency turned out to be thicker or if excessive amounts of water were added.

Acrylic

Stone chips and acrylic resins are used as mineral additives in plaster production. Plasticizers and modifiers are included in the composition. As a result, the coating’s strength and resistance to unfavorable external factors—like precipitation and temperature fluctuations—increase. Up to 25 years longer than mineral plaster, acrylic plaster adheres to polystyrene foam better.

The coating has less chance of cracking because of its enhanced elasticity. Under the effect of mechanical loads, the plaster finish layer atop the polystyrene foam is less prone to abrasion. You can select an acrylic composition based on these characteristics.

• high price;
• low resistance to solar radiation, resulting in color fading;
• increased absorption of dirt.

There are benefits that outweigh the application’s shortcomings. For instance, plaster’s lengthy lifespan justifies its high price. Furthermore, dyeing can be used to return the mixture to its original color if its shade changes. Cleaning acrylic coating is simple (assuming the facade’s height permits).

Features of this finish

Plaster can be used to create a variety of effects, such as "bark beetle" (a coating with a grooved structure), thanks to mineral additives.

• smooth surface is the main disadvantage of extruded polystyrene boards;
• the difference in the thermal expansion of polystyrene foam boards and plaster;
• low hygroscopicity of this type of thermal insulation is the reason for an increase in the drying period of the finishing material, t.to. moisture is not absorbed into polystyrene foam.

These flaws can be removed or refined to the greatest extent feasible.

1. The surface roughness is increased. The desired result is obtained in different ways. You can make a large number of notches over the entire area of ​​the thermal insulation. Another option is to use a needle roller to disrupt the integrity of the surface. Thanks to point damage, the solution will penetrate the structure of the polystyrene foam, which will increase adhesion.
2. Clean the thermal insulation from debris and dust remaining after surface treatment. Then cover the polystyrene foam with a primer.
3. Strengthen the plaster layer with a reinforcing mesh. Use a lightweight version so as not to weigh down the structure. A common variety is fiberglass with a density of up to 160 g / m².

The maximum plaster mix layer is 5 mm, but depending on the material, a coating as thick as 3 mm is typically created.

Because of the characteristics of the base, plaster loses strength and becomes more prone to cracking as it gets thicker.

How to plaster extruded polystyrene foam – technology

It is advised to hold off until the adhesive mixture has dried fully. A layer of thermal insulation will soon be destroyed if a protective coating is applied hastily over it.

Calculating plastering and finishing works

You have to ascertain the material’s volume before you can plan the purchase.

• study the label of the plaster, the manufacturer always indicates the consumption of the mixture per 1 m²;
• determine the surface area of ​​the facade;
• calculate the area of ​​​​window and door openings;
• when determining the amount of material, the difference between the surface area of ​​​​the building facade and window / door openings is taken as a basis;
• the resulting value must be multiplied by the average consumption of plaster when finishing an area of ​​1 m².

It is advised to add another 10% to 20% to the plaster mixture’s volume. This is because, if the material was prepared in large quantities, part of the solution may have spoiled during the preparation process and dried out.

Other unanticipated events (incorrect mixing of the mixture; component proportions are off) can occasionally occur. If only a small amount of plaster is bought, there might not be enough by the time the job is finished, which would lengthen their term.

Preparation of plaster adhesive mixture for outdoor work on polystyrene foam

The proportion of water to dry composition varies based on the type of plaster. The manufacturer’s recommendations, which are listed on the label, should be followed as a guide. Either the solution is prepared separately (by hand-mixing) or it is prepared using a power tool (with a mixer attachment). In less time, you can obtain plaster with the required consistency by choosing the second option. There are no solid fractions and the material is of a higher caliber.

• Pour a sufficient amount of plaster composition into the container;
• Add liquid, and it is important to do this in stages – water should be poured in small portions, constantly stirring the solution;
• When the plaster acquires the desired (creamy) consistency, leave it for 5 minutes to completely dissolve the components;
• Stir the solution again.

Paping with reinforcing mesh

It is advised to focus on the corner areas first. Additionally, they are strengthened. Use of specific metal corners is required. In the event that they are not offered, you can create them yourself using mesh. Slice up to 30 centimeters wide. They are all twisted in the direction of the center. The facade’s corner sections are fixed with improvised mesh corners. Next, use a spatula to smooth the surfaces multiple times. Up to 3 mm of solution should be applied.

Cut the material into pieces that are one meter long in order to reinforce the remaining polystyrene foam surface. Dealing with them will be less difficult.

1. The solution is first applied to 2 sides of the corner of the mesh piece. Layer thickness – 3 mm. Moreover, it is important to completely drown the mesh in the solution.
2. The pieces of reinforcing material are laid with an overlap of 10-15 cm. It is prohibited to place them end-to-end due to reduced reliability.
3. The solution is not applied along the edges. These areas are glued when the next piece of reinforcing mesh is laid. Otherwise, the thickness of the coating layer will increase.

Apply a layer of plaster over the mesh to the entire wall, following the same principle.

Grouting the plaster mesh

A sandpaper-coated float is utilized as a unique tool. Extruded polystyrene foam plastering requires waiting until the mixture containing the mesh is fully dry. Depending on outside variables, this could take as little as 24 hours. (weather, air humidity). The float’s working surface smoothes out tiny irregularities as it is moved in a circular motion. This is required because the thickness of each subsequent plaster layer is small. This makes it impossible to conceal serious flaws. It will be easy to see where the inner layers protrude.

Surface leveling

It is necessary to level the prepared polystyrene foam before plastering. A wide spatula is used for this. Parts of the facade’s surface need to be separated. The mixture is applied to each of them, and the edges shouldn’t line up with the mesh cuts’ perimeter. This will cause the coating to break down quickly. Using a spatula, apply the plaster mixture in the arc’s direction from top to bottom.

It is imperative to form a layer as thick as 3 mm. For surface leveling, the plaster must be applied and smoothed with greater care.

Grouting the second layer of glue

Once the mixture has dried completely, you can move on to this step. However, you are limited to a 4-day wait. The plaster covering the polystyrene foam will fully solidify during this period. Defect removal will become considerably more challenging. A float should be used as well.

• remove large defects with medium-grain sandpaper;
• rub the surface with fine-grain sandpaper.

Primer

Adhesion is enhanced by the use of a unique combination. The adhesion of materials (polystyrene foam, plaster) is improved by primer. Various compositions can be used; the finishing method is taken into consideration when choosing the best option. Using a primer designed for outdoor work is crucial. Mixtures of this group are subject to different requirements.

Facade finishing

• decorative plaster;
• painting method.

All of the options have benefits. Decorative plaster, for instance, makes it possible to conceal flaws. The material’s grain size determines the layer’s thickness. Using a grater or sponge, plaster the prepared surface to complete the expanded polystyrene. If there are no flaws in the plaster’s top layer, painting is the preferred course of action. The appearance of the smallest protrusions, depressions, and curves is encouraged by this option. Thus, the base needs to be level.

It is advised to start finishing as soon as the primer mixture is fully dry. The kind of material will determine how long this process takes. The characteristics of working with soil are indicated by the manufacturer. The application of decorative plaster is done top to bottom. Using a textured roller or a spatula, a relief is made concurrently.

When working with such material, segmenting the surface conditionally is advised. Once the decorative plaster has completely dried, painting can begin.

Consideration	Details
Type of Plaster	Choose between cement-based, acrylic, or silicone plasters. Cement-based is durable, acrylic is flexible, and silicone is water-resistant.
Adhesion	Ensure the plaster adheres well to polystyrene foam. Look for products specifically designed for this material.
Durability	Consider the climate in your area. For harsh weather, select plasters with high durability and weather resistance.
Finish	Decide on the texture and color you want. Plasters come in various finishes, from smooth to rough textures.
Application	Check if the plaster is easy to apply or if it requires professional installation. Some types may need special techniques.
Cost	Compare prices but remember that higher cost can sometimes mean better quality. Balance cost with the other factors.

For your facade’s polystyrene foam, selecting the appropriate plaster is essential to guaranteeing its longevity and aesthetic appeal. It’s critical to choose a plaster that will not only stick to foam well but also endure bad weather and give the desired finish. To prevent peeling or cracking over time, choose a plaster that is made especially for use with insulating materials.

Seek for plasters that exhibit good adhesion and flexibility. These will prevent the plaster from being harmed by temperature fluctuations and enable it to adapt to changes in the underlying foam. In addition, take into account the options for texture and color to complement your preferred style and the overall appearance of your building.

Finally, remember to apply and maintain your product according to the manufacturer’s instructions. Your plaster will perform better and last longer if it is installed correctly. You can make sure that your facade looks fantastic and is protected for many years to come by selecting the right product and applying it correctly.

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