How and how to plaster a foam

Foam surfaces are smooth and non-porous, which makes plastering them a little challenging. However, you can achieve a long-lasting and appealing finish with the appropriate method and supplies. Throughout this process, appropriate products that adhere well to foam are selected to guarantee durable outcomes.

Comprehending the entire process, from surface preparation to plaster application, is essential to completing the work correctly. The quality of your project will depend on the plaster you choose, the tools you use, and the techniques you employ.

We’ll go over the best supplies and techniques for plastering foam in this guide so you can complete the job with assurance and expertise.

Step	Description
1. Prepare the surface	Clean the foam, remove dust and apply a primer to ensure good adhesion.
2. Apply a base layer	Use a special adhesive mix or plaster to create a rough layer that sticks well to the foam.
3. Install reinforcement mesh	Embed a fiberglass mesh into the base layer for extra durability and crack prevention.
4. Apply finishing plaster	Add a smooth top layer of plaster, making sure it’s even and ready for painting.
5. Allow to dry	Let the plaster fully dry before applying paint or other finishing touches.

Expanded polystyrene and penoplex what is the difference

The development of new building materials for use in insulating structures began with the invention of polystyrene. Polystyrene foam, or simply polystyrene foam, was one of the first materials to be used. Penoplex (or Penoplex) was then developed.

Although polystyrene is the raw material for these insulation materials, different production techniques are used:

polystyrene foam is formed by treating polystyrene granules (with or without pressing) with steam, under the influence of which the granules swell (reaching sizes of several mm) and stick together;

Extruded polystyrene foam is known as Penoplex. The two materials are not the same in terms of density, strength, water absorption, or thermal conductivity.

The attributes are displayed in the table to aid in understanding.

Comparison criterion	Foam plastic	Penoplex
Substance – polymer polystyrene, formula (C8N8) n
Production	Steam treatment, pressing	Foaming, extrusion, pressing
Density	Up to 25 kg – 1 m3	Up to 47 kg weighs m3
Thermal conductivity (thermal conductivity coefficient)	Gaps between granules reduce thermal insulation properties – 0.037 to 0.043	Thermal conductivity is almost a quarter lower – 0.03 W*m* C
Moisture permeability (water absorption)	2%	0.4-0.2%
Vapor permeability (vapor permeability coefficient in mg/m×h×Pa)	low	Almost zero, 0.007
Strength:

1. MPa, compression

Bending at 2 MPa

2 – between 0.25 and 0.7,

These materials are made as sheets that are simple to cut, even with a knife.

Can it be used penoplex for walls

Penoplex for floors, walls, ceilings, and foundations can be found on the shelves of a building supply store. After giving in to advertising, it’s simple to incur unnecessary costs. Investigating the matter further makes more sense.

The sensible applications for the foam as a building structure heater are limited by its high cost. You can use penoplex without restriction if the cost is unimportant to the home’s owner, but you shouldn’t ignore the builders’ claims that PP sheets that are 2-3 cm thick will obstruct the cold well’s path.

The area of the facades pasted over using the wet facade method is significant, and the effect of using a thin-layer insulation is negligible, hardly noticeable. Unjustified overspending takes place. This is frequently money thrown into the wind. Using foam plastic and plaster protection afterwards is often more profitable because the owner should save money on insulation.

The wall materials’ operational conditions are an additional justification for rejecting Penoplex. Complete vapor barrier conditions are handled by concrete walls with remarkable ease. The brick and wooden walls crumble more quickly because they can’t expel the moisture that has accumulated in their pores. Therefore, it makes more sense to use mineral wool and polystyrene foam to preserve the house’s primary load-bearing structures.

Penoplex has specific applications. Penoplex sheets are therefore appropriate for insulating shallow-depth foundations or loggias, as well as for insulating the soil beneath the blind area surrounding the house.

If you give in to the builders’ assurances and choose to use penoplex for wall insulation, you will need to dependable external protection for the cladding. Polystyrene foam plaster is used for this purpose.

Why plaster

The following risks are present when a penoplex is opened:

• Birds love to peck, and rodents love to sharpen their teeth;
• exposure to UV rays (when insulating facades);
• mechanical shock or abrasion.

Several techniques are employed to shield sheet insulation from them:

• siding, clapboard, other sheet material;
• finishing with mastics;
• painting;
• plastering.

Penoplex resists exposure to a wide range of chemicals with ease, including any type of plaster.

Consequently, the following queries: can penoplex be puttied at all? The answer to the question "and is plaster penoplex possible?" is in the affirmative.

Therefore, properly plastering the Penoplex facade will not only preserve the insulation but also give the walls a smooth, monolithic appearance and enhance the building’s aesthetics. Plastering with ornamentation can give your home a distinctive look.

Types of mixtures

Selecting plaster for the facade is a challenging task for novices.

Here, there are a number of subtleties that must be carefully considered:

• operating conditions of the insulation;
• compatibility of the base materials, insulation, plaster composition;
• experience of the plasterer (some types of plaster compositions are more difficult to apply);
• the amount of finance intended for the work;
• other considerations.

As a result, understanding the characteristics of the primary plastering materials is essential.

The following are plaster mortars:

• leveling (with filler of different granule sizes) – for puttying (fine-grained), ordinary;
• decorative (used for finishing);
• special (for solving problems of a certain type, for example, sanitizing, acoustic).

By application domain:

• for interior work,
• universal,
• for outdoor conditions – facade.

By the base’s principal binder:

Compositions designed especially for plastering expanded polystyrene have been developed according to their intended use and application location in the Wet Facade system:

• adhesive;
• leveling;
• multifunctional (universal).

Multifunctional products

These kinds of compositions are specifically made to carry out various functions on the Wet Facade apparatus; that is, the plaster-adhesive combination for expanded polystyrene can be utilized for the following purposes:

1. primer composition;
2. mixture for gluing penoplex sheets to the wall;
3. composition for reinforcement (fixing reinforcing mesh on top of polystyrene foam boards); leveling layer.

The cost of this product is higher than that of leveling compounds and adhesive. However, you won’t have to search for each of these compounds made by the same company.

Mineral compounds

Cement and gypsum-based compounds are the most widely used mineral mixtures. Lime and clay are additional binders for plaster.

Benefits of plaster mixtures based on minerals:

• cheapness;
• environmental friendliness;
• strength;
• vapor permeability;
• fire resistance;
• resistance to UV radiation and biodeterioration;
• durability.

• do not tolerate vibration loads, are prone to shrinkage cracks during hardening;
• slow strength gain (cement, lime mixtures).

It is not advisable to cover polystyrene foam sheets with simple cement compounds or use gypsum compounds for facades.

Acrylic

Acrylic resin-based coatings offer the following benefits:

• impact resistance;
• elasticity;
• water resistance;
• easy to install;
• wide selection of shades;
• environmental friendliness;
• average cost;
• durability.

• flammability;
• vapor permeability;
• tend to accumulate static, attract dust;
• fading in the sun.

Silicone

Silicone serves as the compositions’ foundation. As a result, these plasters are the most elastic and long-lasting compositions. Durable, waterproof, and breathable. The primary drawback is the cost. These compositions are the priciest ones. Ideal for producing any kind of effect, but their application is limited by their cost.

Silicate composition

The compositions, which are based on a liquid glass binder, stick to polystyrene foam surfaces quite well.

The following are some of their benefits:

• resistant to chemicals;
• easy to wash;
• vapor permeable;
• durable;
• water-repellent;
• expensive;
• strong.

• require primer and paints on the same basis;
• set too quickly (not for beginners);
• not applicable indoors.

The right materials must be used, along with the right techniques, to plaster foam surfaces effectively. For maximum durability, use reinforcing mesh or a special adhesive after priming the surface to improve adhesion. To create a smooth, even surface, a base coat and a finishing layer of plaster are applied in that order. This method enhances the foam’s insulating qualities and guarantees a long-lasting outcome while shielding it from outside harm.

Specifics of different types of finishing

Penoplex plaster has subtle differences depending on where the house’s insulated structure is located. This first relates to what can be utilized to complete the penoplex.

Finishing the base

The base requires special moisture protection because it is a component of the building structure and is placed directly on the foundation. As a result, extra precautions are taken to guard against water intrusion while also avoiding the formation of cold bridges.

Typically, a thicker layer is used when plastering the base onto expanded polystyrene because:

• a) the likelihood of strong mechanical impacts on the base is higher;
• b) often for the base, the final finishing is done with cladding: stone tiles or pebble plaster (heavier).

A metal mesh is used for reinforcement when heavy cladding is used, and this necessitates a thicker plaster layer. On Penoplex, only facade plaster is used.

How to plaster penoplex indoors

Penoplex insulation is installed indoors if, for a variety of reasons, it cannot be done outside. In this case, penoplex will "eat" less space than polystyrene foam. Gypsum plaster is an appropriate material to use when plastering penoplex indoors or on heated loggias.

These works follow a similar sequence to plastering a penoplex outside; however, installing a base profile is not required. Putty is also used when plastering over a reinforced layer.

The space shouldn’t have any drafts. Moreover, using fans and heaters to hasten the plaster coating’s drying process is not an option. The solution’s strength decreases sharply and shrinkage cracks appear when it is deprived of the moisture required for it to gain strength.

Not only compositions meant for the interior but also plasters on the facade penoplex are appropriate for plastering from the inside.

How to plaster penoplex outside

Use adhesive compositions (for reinforcement) or specialized façade plasters for penoplex when applying plaster to the exterior of the structure. Then, apply appropriate façade or universal plaster compositions on top.

A reinforcing mesh is essentially unnecessary at elevations greater than two meters above the ground. Nonetheless, it’s essential to guarantee that the plaster coating adheres firmly to the PP. Selecting a plaster that "sticks" to the polystyrene foam firmly is preferable.

For example, you can use the plaster-adhesive composition Ceresit CT 85 to glue penoplex plates to the wall and to attach the reinforcing mesh. Ceresit additionally manufactures plaster compositions for ornamental finishing, such as the polymer-cement "bark beetle" (CT-35) and the pebble (CT-137).

Necessary tools and materials

The plasterer’s two primary tools are the trowel (trowel) and the spatula. For work, stainless steel spatulas are preferable. You will require various width tools. For a beginner, it is best to use a wide spatula up to 35 cm. To facilitate easier and faster work, it is recommended to round off the edges of the trowel and spatula blades.

• grater with sandpaper (you can use a plastic one);
• masking tape;
• mixer;
• rule with level;
• knife for cutting penoplex, scissors for cutting mesh;
• roller for primer;
• brushes;
• containers;
• tape measure;
• rags.

• sufficient volume of plaster mix (with a 20% reserve);
• primer;
• mounting foam;
• tap water not higher than room temperature;
• reinforcing mesh;
• special plastic corners with mesh (for reinforcing corners);
• base profile (to cover the top of penoplex cladding, if it is in the middle of the wall).

Preparing the penoplex plane

1. Before plastering polystyrene foam, the surface of the penoplex cladding is inspected.
2. The evenness of the entire surface is checked with a rule. Protrusions must be cut off, otherwise they will show through under a thin plaster layer. And large differences will have to be leveled with plaster composition, which will increase its consumption.
3. All open seams (even narrow ones) must be filled with polyurethane foam, otherwise freezing spots will form in these places – cold bridges. Seams that are too wide are sealed with cut strips of penoplex of the required width and monolithic with foam. Excess foam is carefully cut flush with the surface.
4. Remove dirt from the surface, sweep away dust or remove with a damp cloth.
5. Sink the caps of the dowels with which the sheets are attached below the surface. Apply the solution on top of them (flush with the surface).
6. It is advisable to make the surface of the thermal insulation rough. To do this, scratch it with a brush, sandpaper or roll it with special needle rollers.

How to properly plaster penoplex – technology

We will then work out how to plaster the penoplex.

Initially, the following circumstances are noted:

• choose windless, not hot (below +30 ° C), dry weather with an air temperature above +5 ° C;
• the workplace is shaded from the sun and protected from precipitation.

Penoplex exterior plastering is comparable to foam plastic exterior plastering.

Using the Wet Facade technology, plastering polystyrene foam is done in phases:

1. preparation of the surface of the mounted PP;
2. priming;
3. preparation of the solution;
4. application of the adhesive solution;
5. attachment of the reinforcing mesh;
6. rubbing;
7. application of the leveling layer;
8. priming;
9. preparation of the decorative solution (preparation of the ready mix);
10. application of the finishing decorative plaster;
11. painting.

Preparation of the solution

In accordance with the instructions, plaster compositions meant for plastering polystyrene foam surfaces are diluted. Pouring the dry mixture into a container filled with water that has been preheated (start with less liquid than needed for the entire solution). A mixer is used to perform mixing. If needed, add more water. The solution is mixed and used after being left for five minutes to ensure uniform mixing.

Before using, ready mixtures must be agitated to lift the heavy filler particles that have settled.

Installation of reinforcing mesh

The technology is easy to use. Installation must begin at the corners. Using a spatula, apply adhesive solution to the corner (from both sides of the corner). Apply the corner, push it into the solution, and then use a level to ensure that it is vertically pressed into the mixture. If there is mesh at the corner, glue is applied underneath it beforehand. Using a spatula to smooth it out, the mesh is leveled and pressed down onto the solution, pressing it into the mixture.

After strengthening the walls’ corners and slopes, the mesh is fastened to the wall’s flat areas.

1. First, draw a horizontal line of the top of the reinforcement on the wall.
2. Use a wide spatula to apply a layer of adhesive solution to the area adjacent to the corner of the wall.
3. “Structure” the solution with a notched trowel.
4. Apply the mesh, starting from the drawn line. Align it along the corner, press it in several places to the solution by hand.
5. Smooth with a spatula, from top to bottom and from the center to the edge so that the solution comes out through the cells. The excess is removed or refilled in places where there is not enough solution. As a result, the mesh should be completely immersed in the solution.
6. Apply glue to the area next to it. Apply the mesh with an overlap of 10 cm of the edge on the previously laid mesh sheet. Smooth it with a spatula.
7. When all the sheets are plastered, the surface is dried.

Using a spatula, they attempt to even out the mesh so that fewer imperfections will ultimately need to be sanded down.

Plastering

The plaster layer should completely enclose the reinforcing mesh. A solution ought to exist underneath and above it. Consequently, 2-3 mm of plaster-adhesive solution is applied with a spatula following its installation and fixation. Using a wide tool for this is preferable. The surface is dried after every sheet has been plastered.

Grouting and leveling

The surface is rubbed down and any sharp protrusions are sanded using a grater and sandpaper in a circular motion after a 24-hour drying period. Over the whole surface, the pressure is maintained constant.

The following finishing determines the sandpaper’s grain size selection:

• large grain for decorative structural plaster;
• fine grain – for painting and wallpapering, and if the decorative plaster is applied in a thin layer.

Dust off the grout after grouting.

Applying decorative plaster

Penoplex can be painted with decorative solutions without plastering after it has been leveled. Plaster decoration, however, appears more appealing. Completing the wall plastering will provide extra security.

Is priming necessary? Which primer is appropriate for use with plaster? The surface is primed prior to applying decorative compounds to the penoplex. Compounds that are appropriate for leveling and decorative solutions are chosen for these works.

When working with a roller is inconvenient, a roller and brush are used to apply the primer composition.

The "layer cake" is dried before the decorative layer is applied.

The application of a decorative solution is done so as to produce the intended effect. Rain, fur coats, travertine, and bark beetles are frequently seen on the facade. There is a wider selection of effects for premises.

Than to paint the foam

It was now my turn to answer queries. Could the foam sheets that had been plastered be painted? Which combination is suitable for use outside the home?

You are not permitted to use paints or varnishes that contain:

• benzene;
• kerosene or gasoline;
• toluene;
• acetone;
• Oolif;
• coal resin;
• xylol;
• polyester resins.

All of these materials demolish polystyrene foam by piercing through the thin layers of reinforced plastering coating. It is preferable to select paints that are silicate, water-based, and contain mineral fillers. They are all appropriate for both external and internal offices.

Famous manufacturers

The following businesses manufacture the most well-known brands of polystyrene foam for plastering:

• Sto AG concern (Germany) offers a line of Stolit plaster mixes;
• Henkel concern (Germany) produces Ceresit plaster mixes;
• Ecomix company produces the same-name mixes for wet facades.

A series of products from the German company Sto AG’s Russian subsidiary:

• Sto-Baukleber (for gluing polystyrene foam);
• StolevellDuoplus or Uni (for gluing and reinforcing);
• StoPutzgrund or StoPrep Miral (intermediate priming);
• Sto-Strukturputz or StoMarlit (finishing plaster mixes).

• adhesive for mounting polystyrene foam – BS-113;
• plaster-adhesive composition for making a reinforced layer on top of the slabs – BS-106;
• quartz primer – BS-707;
• for finishing – decorative mixture "bark beetle" BS 208 or pebble BS

The "Warm Wall" line, produced by the German company Knauf, consists of the following compositions:

• Sevener (plaster-adhesive);
• Decorgrund (primer);
• Diamond (decorative).

To achieve a long-lasting and beautiful finish, plastering foam surfaces requires careful attention to detail and the appropriate materials. Foam surfaces can be effectively protected and enhanced in appearance by using the right products and following the right procedures.

Always begin by meticulously prepping the foam surface. For excellent adhesion and long-lasting results, proper priming, cleaning, and reinforcement are essential. A high-quality plaster mix made specifically for foam applications can have a big impact on how things turn out.

A smooth and polished finish depends on several key elements, including working in layers, taking your time when applying, and allowing enough drying time. Plastering foam surfaces for both functional and aesthetic reasons can be accomplished with confidence if you take the appropriate approach.

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