Plaster for polystyrene - features of the material and its use
Insulation made of expanded polystyrene and similar materials needs to be finished to protect it from mechanical stress, moisture, ultraviolet rays and other adverse factors. Most often, plaster for polystyrene is used as such protection, forming a durable moisture-proof layer on its surface, which serves as a reliable basis for decorative cladding.
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How to plaster polystyrene
The structure of polystyrene is porous. It represents styrene granules filled with gas, tightly bound and pressed to each other.
However, over time, under the influence of external factors such as precipitation, high humidity, temperature changes and the sun's rays, these bonds weaken and the material begins to break down.
Its mechanical strength is very low - the plate can be easily broken or crushed with your own hands. That is why the material needs a protective shell, which is created by plastering the surface.
In construction, in addition to conventional polystyrene, other similar materials are often used. For example, extruded polystyrene foam, during the creation of which the granules melt, turning into a homogeneous substance with strong molecular compounds. Or polystyrene concrete - concrete blocks in which up to 75% of the volume is filled with polystyrene granules.
Wall plastering from polystyrene concrete, conventional and extruded polystyrene is carried out according to the same technology and special compositions designed specifically for such surfaces. They have special properties that special additives allow to achieve.
Tip. Do not take chances by purchasing ordinary plaster for such work or trying to make it yourself. Buy proven materials on the packaging of which there is an indication of the possibility of use on foam and similar surfaces.
Mineral plasters
Mineral plaster for polystyrene is made from white Portland cement, lime hydrate and mineral fillers are used as additives. Its disadvantages include the appearance of cracks on the surface and a short (up to 10 years) service life.
The positive properties of the material are much greater.
It:
- Frost resistance - the ability to endure frequent cycles of freezing and thawing without loss of strength and other characteristics;
- Resistance to moisture;
- Good vapor permeabilityallowing structures to "breathe" while maintaining a favorable microclimate in the premises;
- Fire safety, incombustibility;
- High adhesion - property to adhere to the surface of the base;
- Low price;
- Environmental friendliness - does not contain toxic substances;
- Easy to care.
Acrylic plasters
Mineral binders, plasticizers and modifiers are also added to plasters based on a water dispersion of acrylic resins. In addition to their high cost, they are distinguished by complex care: the surface that easily absorbs dust and dirt is cleaned only with the use of detergents.
But:
- Acrylic plaster is easy to apply;
- It has high elasticity and the ability to stretch, which prevents the appearance of cracks;
- It has high strength to mechanical stress;
- Reliably adheres to the base, does not exfoliate;
- Creates a vapor permeable coating;
- Serves 2-3 times longer than mineral plaster.
Since the instruction for plastering polystyrene provides for the installation of a reinforcing layer of fiberglass mesh, then the described mixtures may vary not only in composition, but also in application.
Most manufacturers produce different materials for gluing the mesh and for creating a decorative coating on top of it. In this case, a solid granular filler is introduced into the decorative plaster, which forms a relief on the surface during application and grouting.
But there are universal mixtures suitable for creating both a reinforcing and a decorative layer.
Technology for plastering polystyrene surfaces
As in the case with the finishing of all other types of surfaces, the plastering of polystyrene concrete blocks and walls insulated with polystyrene foam consists of several stages.
Preparation of materials and tools
Before buying materials you need to calculate the surface area to be trimmed. This is necessary to calculate the amount of plaster, primer and reinforcing mesh. As a rule, on the packaging of any building mixtures there is information about the consumption per 1 sq.m., you should focus on it.
The following information will help you decide in advance:
- Universal plaster depending on the thickness of the layer may require 4-6 kg per square meter. Accordingly, when buying separately adhesive and decorative compositions, the consumption of each of them will be 2-3 kg.
- Primer consumption depends on its type. In the case of using universal plaster, ordinary penetrating soil is suitable, and under the finish with a decorative composition - concrete contact primer filled with quartz sand.
- The reinforcing mesh is bought taking into account the fact that each strip is glued with an overlap of at least 10 cm to the previous one.
Tip. Get material with a margin of about 10-15%. This is especially true for building mixtures, since all finishing should be carried out with the same brand of material. If you do not have enough plaster, and you can’t find the same on sale, the quality of the surface finished with different compositions may suffer. Keep receipts so that you can return unused material in the whole package back to the store.
From the tools, prepare:
- Set of spatulas;
- Paint roller and brush;
- Grater with an emery cloth;
- Building level;
- Mixing tank and drill with mixer nozzle.
Solution preparation
The working solution from the dry mixture is prepared according to the instructions on the packaging using a construction mixer or drill with a special nozzle at low speeds to avoid the formation of air bubbles.
It is important. Pay attention to the recommendations on the time of use of the solution, the viability of which is quite limited.
After opening the packaging, it is enough to mix the finished acrylic compositions.
The device of the reinforcing layer
We proceed directly to how to plaster polystyrene. First of all, a reinforcing mesh is attached to its surface, which is glued to the adhesive or universal composition in the following sequence:
- Cut strips about 30 cm wide to reinforce external corners and slopes. Bend it in half in length;
- Apply the plaster to the corners with a layer of no more than 3 mm and stick the mesh, pressing it into the solution and smoothing it from the corner to the sides and down;
- Put the solution on solid sections of the wall and roll the net over them, also pressing it into the crude mixture so that it completely “drowned” in it;
- Smooth the surface with a wooden or metal grater, removing wrinkles and bubbles and achieving extrusion of the solution through the mesh cells for its reliable fastening;
- Allow this layer to dry for a day, and then polish the surface with a grater with an emery cloth attached to it.
Finish layer device
After grouting, the surface is coated with a primer using a roller, allowed to dry and a topcoat is applied. The work is carried out in the usual way: with a small spatula, the solution is collected from the container, transferred to the blade of the wide working spatula with a sliding movement, and then distributed over the wall.
The layer should be thin, about 3 mm. In the case of using decorative plaster, the thickness of the layer should be approximately equal to the diameter of the grains of the filler.
The plaster is also allowed to dry for 3-4 days, after which it is ground and primed for subsequent finishing - painting or decorative finishing.
Conclusion
Polystyrene is a practical and inexpensive material with which you can significantly increase heat saving in homes and reduce heating costs. But he himself needs mandatory protection from rains, frosts and heat. The video in this article will tell you in more detail how to properly provide such protection by independently performing all the activities related to it.
