Plaster

Properly applied plaster reliably protects and levels the outer surfaces of walls even in the worst operating conditions. And inside buildings, it serves as a durable and hygienic coating.

Finishing work on interiors and façades must be carried out at an ambient temperature of not less than +5°C but not more than +30°C.

Plastering works are carried out in several stages:

1. Prepare the base:

If there are foreign inclusions on the surface, remove them mechanically or roughen the base with a wire brush or a scraper.
Clean the surface from dust and dirt.
Remove peeling and weak materials with a metal tool (a spatula or a trowel).
If the base has a high absorption capacity (ceramic bricks, aerated or foam concrete blocks), moisten it with water.
Primer the base.

2. Install screed strips to ensure even application.

Set the vertical position of the extreme strip.
After setting the level, immobilise the profile.
Install the extreme strip in the same way.
Install other guides in the plane formed by the two extreme screed strips, with a step at least 10 cm shorter than the length of the screed board you are using.

When working with cement-sand mortar, it is not recommended to attach the strips with gypsum binders.

3. Apply plaster, usually in three layers:

The spray layer ensures strong and uniform adhesion of the following layers of plaster to the surface. It is best to create it by throwing the mortar at the wall with a special mortar ladle or scoop without further levelling or smoothing. The layer should be 3-5 mm thick.
The base layer is the most critical stage of plastering. It protects the wall from mechanical and atmospheric influences. This layer should be no more than 12 mm thick. Be sure to smooth it out with a screed board.
The outer (facing) layer should be either thinner or less rich than the base layer and no thicker than 10 mm. After the facing layer has dried up a little, use a plastering float or a finishing trowel to smooth out uneven areas and cavitations to obtain a uniform, even flat surface until the sand shows.

Select and attach a wire mesh if required by the type of work, the mortar, the kind of base, and the wall's unevenness.
Each subsequent layer should be weaker than the previous one. To do this, reduce the strength of the mortar by decreasing the content of cement or reducing the thickness of the next layer.

Increasing the thickness of any layer of plaster will not provide the wall with additional protection from weathering or other influences. Still, it may lead to the plaster cracking or falling off due to shrinkage or poor adhesion between the layers.

4. Prepare the mortar

Use graded sand without clay. It has a significant effect on the quality of a surface.
Add cement and mix it with the sand. For plaster mortars, it is practical to use cement of strength class 400. CEMARK UNIVERSALNYI and CEMARK MITSNYI are the best choices for this type of work.
Add water.

The standard proportions of materials in a mortar depend on the application:

Application	Mortar strength class	Cement	Sand
Foundations, façades, floor screeds	М 200	1	2
Foundations, façades	М 150	1	3
Interior finishing	М 100	1	4.5
Outer (facing) layer of exterior walls, the base layer of interior walls	М 75	1	5.5
Outer (facing) layer of interior walls	М 50	1	7.5