When talking about plasters, we must first clarify how they differ from screeds, as they are similar concepts in construction. The main difference is that plasters are applied to the walls of a room, while screeds are applied to the floor.
TYPES OF PLASTERS
In general, there are two types of plasters: external and internal. External plasters are silicate, silicone, mineral and polymer. Internal plasters are divided into lime-gypsum and lime-cement.
WHERE ARE LIME-GYPSUM PLASTERS SUITABLE?
Lime-gypsum plasters are for interior use only. They dry faster and are suitable for rooms with normal humidity. This type of plaster is a coating to achieve smooth, paintable surfaces.
WHAT TOOLS ARE NEEDED TO APPLY PLASTER?
The necessary tools that everyone should have when they want to do plastering easily and correctly are the following:
1. Trowel, putty knife, trowel, trowel (large plastering trowel), bucket, 2-3 buckets (plastic) or a large black plastic basin to have somewhere to mix the mortar.
2. Drill and mixer.
3. The most important attributes are a good level and an aluminum ruler. The ruler should be about 2 m long. It can also be 1.50, 1.80, 2.50 - decide what size you will need. It is best to have different sizes - one 2.50 m, one 2.00 m and one 1.50 m.
HOW TO PREPARE THE BASE WITH PRIMER?
The base must be clean, dry, frost-free, dust-free, free of salts (mineral salts), not water-repellent, have the necessary load-bearing capacity and not crumble.
Priming is an operation that prepares the base for applying gypsum plaster. The primer (concrete contact) performs several important functions. It penetrates deeply and strengthens the base, equalizes its ability to absorb moisture, improves adhesion between the base and the plaster, isolates the base against the penetration of harmful substances, gives it hydrophobic properties and protects it against the penetration of moisture, evens out its coloring, which is important for light plasters. It is best to use a primer colored according to the color of the plaster or to choose the classic solution - white. The primer is applied with a paint roller or brush evenly over the entire surface.
For highly absorbent or unevenly absorbent substrates such as baked bricks, it is recommended to prime with an absorption leveling agent diluted with water in a ratio of 1:3. The technological waiting time is at least 12 hours (depending on temperature and weather conditions). If the substrate is made of aerated concrete, it is also recommended to prime with an absorption leveling agent diluted with water in a ratio of 1:2. The technological drying time in this case is at least 24 hours (depending on temperature and weather conditions).
If the foundation is made of cement-bonded masonry blocks, it does not need to be pre-treated.
WHEN IS PLASTER REINFORCEMENT APPLIED?
When changing materials in one plane, for example concrete and masonry or different stone walls, it is recommended to reinforce the plaster in the transition area. Then the corner strips/profiles are placed. They are plastered with cement/gypsum mortar.
HOW IS THE WALL PLASTERED?
Before applying the plaster, to facilitate work, stainless steel protective profiles are installed on all corners and edges. The application of lime-gypsum plasters is usually carried out in strips (with a minimum thickness of 10 mm and a maximum of 25 mm on each side). It is pulled out and leveled with an H-strip and after it has “pulled”, it is cut off with a flat trowel, moistened evenly with water and smoothed with a sponge trowel. After another short drying time, the surface is smoothed once again with a suitable tool. In the case of large thicknesses (for example, with uneven surfaces) after the first layer has gained strength, depending on the substrate (10-20 minutes), the next layer of plaster should be applied “wet on wet” to the required final thickness.
How exactly is plastering done?
To plaster a wall, you need to lay "mothers" (stupas). You need a level and a level, which are placed vertically on the wall, measuring its straight line. The eye of the level should be exactly in the middle of the two lines at equal distances. This way you can understand where the wall is most crooked, respectively straightest, and start laying the stupas. To make a stupa, you must first place two fixators at its two opposite ends, which are glued with construction gypsum/cement mortar. In construction language, this is called "chickens". The gypsum is spread in balls (consistency - like soft clay) at both ends of the "mother", which is leveled vertically and left to dry for 1-2 days.
Plaster is applied along the axis formed between the "mothers" and their extension outside them, i.e. from the ceiling to the floor (so as not to introduce air - to avoid bubbles). After applying the solution, it is necessary to press it with a surface spatula (butterfly) or a long trowel with horizontal movements left and right and then smooth it with an h-tread along the vertical of the two chickens (corner strips). After 30-40 minutes, when the plaster has gained strength, with a trapezoidal spatula above the level of the "chickens" (corner strips), the excess plaster is pulled off the wall in the direction from the ceiling to the floor. To make the plaster smoother, after 2-3 hours it is wetted abundantly with water and smoothed with a foam, wooden or plastic trowel or cotton wool. Then it is smoothed with a trowel without removing material.
The screed is spread with uniform circular movements of the spreader with uniform pressure on the base. This way the treated surface becomes stronger, denser (without holes) and last but not least - more beautiful.
Next comes the application of final coatings: putty, paint, wallpaper.
HOW LONG DOES IT TAKE FOR THE PLASTER TO DRY?
The temperature of the air, material and base during application and during the hardening process must be above +5°C. When using heating appliances, especially gas-powered ones, good ventilation of the surface must be ensured. Direct heating of the plaster is inadmissible.
For gypsum-containing plasters, continuous drying must be ensured within the first 14 days to prevent the formation of a glazed, low-absorbent surface. Subsequent wetting or water seepage through the plaster during the drying and setting process of the plaster must be prevented (e.g. from condensed water, absorption of water from subsequently applied floor screed, etc.).
Electrical and installation ducts should be filled in a timely manner with a suitable gypsum-containing material. When combined with other wall or ceiling materials (especially flat roofs, roof structures and stairwells), it is necessary to fill a thin separation joint (e.g. with a trowel) to the base of the plaster.
Surfaces on which ceramic coatings will be applied should not be sanded or smoothed.
Before applying each subsequent coating, the lime-gypsum plaster must be completely dry and properly primed depending on the type of coating.
IMPORTANT! The plaster must be stored on wooden pallets/slats to prevent the integrity of the bags from being damaged and to prevent it from absorbing moisture from the floor.
ADVANTAGES AND DISADVANTAGES OF LIME-GYPSUM PLASTERS
Advantages:
- Easy and convenient to apply (the plaster sets quickly);
- Single-layer application;
- Does not burden the structure (it is light);
- Subject to repair (correction);
- Gives a vision of completeness (smoothness);
- Does not shrink when drying (elastic and no cracks appear).
Disadvantages:
- Silicate paint (nanopor plaster) cannot be applied as a final coating.
WHAT DO WE OFFER?
With us you can find lime-gypsum plasters from the KNAUF and BAUMIT brands with different characteristics, reflected in their personal technical data sheets.
The prices are affordable.
