Warm plaster: insulation for the walls of the house

Recommendation points

• Features and properties of warm plaster
• What is included
• In what systems of insulation to use
• Surface preparation
• Plastering
• Self-cooking
• Decorative value

Increasingly, individual insulation technologies are used for finishing materials that combine decorative and heat-saving properties. Today we want to tell you about one of these materials: warm plaster. Let’s talk about its properties, pros and cons, as well as the method of application on the walls.

Features and properties of warm plaster

Very often, according to the data of heat engineering calculations, a sufficiently large thickness of insulation is required – from 100–150 mm. This explains the development of such building materials as porous concrete and PCB: the enclosing walls of them combine both load-bearing and heat-saving properties. It is quite predictable that the same approach began to be used in the production of materials for decoration..

It is noteworthy that warm plaster has the simplest application technique, in which the final quality practically does not depend on the level of skill and experience of plastering. This makes it available for development and use by construction enthusiasts, and new workers are able to quickly reach the required skill level..

Judging by the declared characteristics, warm plaster has a surprisingly harmonious combination of technical qualities. It has a thermal conductivity comparable to foam-polymer insulation, while it does not include harmful volatile formations in its composition. In this respect, only expensive PIR and PUR boards or spraying can compete with it. The environmental friendliness of materials makes it possible to use warm plaster for interior decoration.

With all this, the plaster absorbs about 1–3% moisture after 100-day direct contact with water without excessive pressure, which gives it almost absolute frost resistance. Hydrophobicity, however, does not imply hindering the infiltration of air and water vapor, and therefore, almost all known thermal insulation systems are in the field of application of warm plaster. Finally, a layer of plaster, with a sufficiently large thickness, can form a finished surface for finishing, which does not require subsequent decoration or leveling. Plaster can also be sanded down to very low roughness. But how much does this range of qualities correspond to reality??

What is included

In essence, warm plaster is no different from ordinary plaster with the exception of one feature. The standard filler (sand) in it is replaced by a more porous material with a closed cell structure. In the traditional version, expanded perlite or vermiculite is used, more advanced brands of mixtures are based on granular foam glass, sometimes reinforcing polymer fiber is included in the composition.

Expanded vermiculite

Of course, it cannot do without modern polymer chemistry. Warm plaster includes a wide range of water-borne modifiers. These are both plasticity enhancers and air-entraining agents, almost always in the composition there are water repellents that protect the plaster from getting wet.

Granulated foam glass

The most common Portland cement is used as the main binder, but there is one peculiarity. The binder content is 80–85% by weight, that is, the ratio of cement to filler comes out equal to 1: 5 – 1: 6. With the declared characteristics of strength, hardness and adhesion, the cement must be of premium quality: a grade not lower than 400-D0 or 500-D5, the presence of hydrophobic properties is optimal. Also, in order to improve the decorative qualities of the surface and paintability, a white binder (PCB) or a mixture of binders of two types is used together with ordinary “Portland cement” (PC).

In what systems of insulation to use

As you know, many heaters require outdoor air ventilation. The intensity of air exchange should be high enough so that water vapor does not have time to condense and freeze, but evaporates freely outside.

One of the main rules in the layout of any insulation cake is that the gas exchange of each layer is always slightly lower than the permeability of the layers closer to the outer surface. The point is that a layer of decorative trim can significantly slow down the free release of moisture..

Since after setting the warm plaster is nothing more than low-density porous concrete, its natural vapor permeability is about 0.2–0.22 mg / m · h · Pa. That is, it limits the gas exchange of porous concrete insignificantly, which means it can also be used for warming brick or concrete buildings. Due to air-entraining agents, the porosity increases with very little damage to hydrophobicity and the throughput can be increased to 0.4–0.55 mg / m · h · Pa. Thus, even mineral wool can be covered with warm plaster, provided it has a sufficiently high density and compressive strength..

For frame buildings, warm plaster is also quite applicable: even in the absence of open air pores, its vapor permeability is comparable to that of wood. The main catch here lies in the fact that a sufficiently high accuracy of the proportions of modifiers is required to give the necessary properties. Therefore, you should pay attention only to certified products: even a slight violation of the production technology of the mixture can deprive the finish of the declared qualities and make its use for individual buildings unacceptable. Unfortunately, the customer will not find out about this until the insulation is completely damaged..

Surface preparation

Now you know that only high-quality formulations of proven brands can be used, this is the first component of a successful result. The second is the exact adherence to the technology of performing work, which is simple, but requires strict adherence to a number of requirements.

With sufficiently high adhesion values, the plaster remains sensitive to hydrophilic and dusty surfaces. Since cement remains the main binder, the principle of hardening of warm plaster is hydratic, that is, it requires not air, but an abundance of moisture. For this reason, the absorbency of the bearing surfaces should be limited by soaking, priming with deep-penetrating compounds or preliminary plastering..

Surfaces with depressions and depressions, such as rubble brickwork, should be pre-plastered to reduce consumption. All preparatory plaster coats are applied only after priming. For slab and mineral insulation, the only limitation is the peel strength. With a density of 300-400 kg / m³ warm plaster adheres to most substrates with a pullout force of 50–70 gf / mm², that is, even a layer of 10–25 cm will be attached to the base with a solid safety margin. For this reason, the strength and quality of adhesion of the insulation to the supporting base cannot be lower than the tear-off load with the used layer of insulation. For reference, note that warm plaster is 3-4 times lighter than ordinary.

Plastering

Plaster is applied in exactly the same way as most gypsum compositions for leveling walls. A trowel, a wide spatula is used, it is possible to throw and align along the beacons.

Most brands of warm plaster allow the use of automatic spray plastering machines. In this case, you need to understand that the density of the mixture without air-entraining agents will be so high that the vapor permeability when compacted by spray will drop to almost zero. It is also recommended to maintain the working pressure in the machine recommended by the manufacturer of the mixture..

Warm plaster can be applied in layers of 35-50 mm at a time, eliminating even very significant differences in the plane of the walls. In practice, a layer larger than 100 mm is rarely used, however, objects with 3–5 years of operating experience show exemplary preservation of the original qualities even at these thickness values. The plaster retains a high limit of irreversible deformation after drying and is not very susceptible to cracking. But even with such qualities, it is often reinforced in layers with a facade mesh or polymer fiber is added to strengthen the structure..

The basic rule in finishing with such compounds is to prevent the layer from drying out before its final setting within 36–48 hours. The surface should remain damp the longer the thicker the applied layer. In some cases, you can recommend covering with a film to create a greenhouse effect and occasionally sprinkling the walls with water. After drying, the surface must be impregnated with a deeply penetrating primer.

Self-cooking

The elementary material base for the production of warm plaster makes it highly tempting to prepare it yourself. We hasten to disappoint: mixing vermiculite with cement in a barrel does not mean getting a composition with such high operational parameters. The maximum that can be obtained is a lighter plaster with reduced thermal conductivity.

This does not mean that independent preparation of warm plaster is impossible, but the expediency of this venture is questioned. The main problem is purchasing components of sufficiently high purity and quality. If the filler was not supplied in a pre-packaged form, it must be repeatedly washed with water and dried well. We mentioned the second problem above: it is quite difficult to find a really high-quality cement with a precision clinker composition..

The third aspect is modifiers and additives. They are not difficult to acquire, but the proportions should be carefully calculated, and, as you know, the smaller the volume of the mixture, the more difficult it is to adhere to the exact ratio of ingredients. If you increase the concentration of plasticizers, the liquid may either be too heavy for the blowing agents to work, or it will slide off the wall due to reduced adhesion. An increase in porosity can lead to an increase in water absorption, and too much cement will lead to increased brittleness and severely limit the thickness of a single application.

Decorative value

In appearance, the surface of the warm plaster is unremarkable. It has a slight roughness and a light gray to white color. In principle, the surface itself does not require any finishing, but it can be improved by invoicing, by spraying a “fur coat”. You can also apply any facade plaster with an acceptable vapor permeability index..

Warm plaster can be painted and re-painted. Do not use film-forming paints such as alkyd or silicone enamels. An acrylic dispersion containing marble or granite dust is best suited. After every 3-4 applications, the layer of paint can become so large that it slows down gas exchange in the underlying layers. In this case, it is sufficient to sand the surface..

In interior work, warm plaster is most often used to insulate slopes and to increase the thermal protection of external walls in apartments. Internal partitions can also be plastered to increase noise absorption. It should be remembered that plaster does not absorb moisture and therefore is less involved in regulating air humidity, in contrast to gypsum compositions.