Lesson 10. Steps to Achieve Q1–Q4 for Brick, Concrete, and Reinforced Concrete Panels

Work with decorative plaster begins long before you open a bucket of material. The quality of the future décor directly depends on how well the base is prepared: which mixtures are used, how they are applied, whether drying times are observed, and whether material compatibility is respected. At this stage, the character of the surface is defined — its strength, stability, and ability to hold the decorative layer without defects.

Many mistakes that appear during application of décor or months later in use originate here — at the stage of rough preparation. Therefore, understanding the properties of plaster and putty materials, their purposes, and limitations is not just technical knowledge, but an essential element of craftsmanship.

In this lesson, we will examine in detail the methods of achieving different preparation levels using construction mixes. You will learn which steps are required when preparing brick, concrete, and reinforced concrete bases in rooms with low, medium, and high humidity to reach any level from Q1 to Q4. This knowledge will help you better understand the process of improving the flatness and smoothness of rough walls.

The main mineral materials used for rough walls are:

• Brick
• Concrete (monolithic walls)
• Reinforced concrete panels (panel houses)
• Foam block and aerated concrete block
• Polystyrene concrete block
• Expanded clay block

Note: Construction traditions vary across countries. In Europe and the CIS, walls made of brick, concrete, and block materials are very common, so plaster and putty preparation systems are widely applied. In the United States and Canada, residential construction has historically developed around wood‑frame building methods, where drywall (gypsum board) is the dominant material. Walls made of concrete, reinforced concrete panels, or brick are less common in homes, but they do exist in certain types of buildings.

Understanding the preparation systems for mineral bases is still important, because the principles of adhesion, smoothness, and durability apply universally. Later in the course, we will also discuss drywall, so you will see how the same quality evaluation principles are applied in North American construction traditions.

Each of these materials has its own characteristics that must be considered when choosing plaster and putty mixes. This ensures not only reliable adhesion but also a durable and aesthetically pleasing decorative finish.

Since preparation of some mineral bases is almost identical, we will divide them into two groups and create an algorithm for achieving Q1–Q4 for each. The first group includes brick, concrete, and reinforced concrete panels. The second group includes foam block, aerated concrete, polystyrene concrete, and expanded clay block. In this lesson, we will focus on the first group, and in the next lesson we will discuss the second.

Brick, Concrete, Reinforced Concrete Panels

Brick Brick is a man‑made construction material in the form of a rectangular block, intended for building walls, partitions, and other structures. It is produced from clay, sand, lime, cement, and other components, which are molded and then fired or pressed to achieve the required strength.

Main types of brick used in construction:

• Fired clay brick — the classic option, with high strength and durability. Widely used for load‑bearing walls and facades.
• Silicate brick — made from a mixture of quartz sand and lime. It has good sound insulation and frost resistance, but is less resistant to moisture than fired clay brick.

Concrete (Monolithic Walls) Concrete monolithic walls are load‑bearing structures created by pouring concrete mix into specially prepared forms (formwork) on the construction site. Once hardened, the mix forms a solid, continuous structure. This method allows walls of almost any thickness and configuration to be built, ensuring high strength and durability. Monolithic walls also provide good sound insulation and resistance to loads, making them a reliable base for further preparation with construction mixes.

Reinforced Concrete Panels Reinforced concrete panels (used in panel houses) are large construction elements produced at factories from concrete mix reinforced with steel rebar for strength. On site, the panels are mounted onto a prepared foundation. They are connected with steel anchors and welded joints, with seams filled with mortar to ensure tightness and strength.

Preparation of Brick, Concrete, and Reinforced Concrete Walls in Rooms with Low and Medium Humidity

If any step differs depending on the base material, it is noted in parentheses. This way, the difference is immediately visible without comparing separate lists.

Q1

1. Surface cleaning and application of deep‑penetrating primer (brick). Surface cleaning, application of deep‑penetrating primer, and application of bonding primer (concrete and reinforced concrete panels).
2. Application of gypsum plaster using installed guide profiles.
3. Leveling plaster with a straightedge.

Q2

1. Surface cleaning and application of deep‑penetrating primer (brick). Surface cleaning, application of deep‑penetrating primer, and application of bonding primer (concrete and reinforced concrete panels).
2. Application of gypsum plaster using installed guide profiles.
3. Leveling plaster with a straightedge.
4. Leveling plaster with a trowel.
5. Smoothing.

Q3

1. Surface cleaning and application of deep‑penetrating primer (brick). Surface cleaning, application of deep‑penetrating primer, and application of bonding primer (concrete and reinforced concrete panels).
2. Application of gypsum plaster using installed guide profiles.
3. Leveling plaster with a straightedge.
4. Leveling plaster with a trowel.
5. Smoothing.
6. Application of deep‑penetrating primer.
7. Application of a continuous layer of gypsum or polymer putty up to 1 mm.
8. Sanding putty with 120 and 180 grit abrasives.

Q4

1. Surface cleaning and application of deep‑penetrating primer (brick). Surface cleaning, application of deep‑penetrating primer, and application of bonding primer (concrete and reinforced concrete panels).
2. Application of gypsum plaster using installed guide profiles.
3. Leveling plaster with a straightedge.
4. Leveling plaster with a trowel.
5. Smoothing.
6. Application of deep‑penetrating primer.
7. Application of a continuous layer of gypsum or polymer putty up to 1 mm.
8. Sanding putty with 120 and 180 grit abrasives.
9. Application of deep‑penetrating primer.
10. Application of a continuous layer of polymer putty up to 0.5 mm.
11. Sanding putty with 240, 320, and 400 grit abrasives.

Differences in Preparation: Brick vs. Concrete

As seen in the preparation steps for brick, concrete, and reinforced concrete walls in rooms with low and medium humidity, the only difference is at the first stage.

• For brick bases, only deep‑penetrating primer is applied.
• For concrete and reinforced concrete bases, in addition to primer, a bonding primer (often called betonokontakt) is applied.

This bonding primer forms a separating layer between the base and the gypsum plaster. Its main function is to create a chemical barrier that prevents the formation of the mineral ettringite. Ettringite expands in volume and literally “pushes” the gypsum plaster layer away from the base. As a result, adhesion is lost, and the plaster can completely detach from the wall.

This situation most often occurs under moisture exposure, for example, during flooding caused by leaks from above. That is why gypsum plaster is not recommended in bathrooms: not only because of gypsum’s low moisture resistance, but also due to the increased risk of flooding in such rooms. A plaster layer applied in several passes can reach 5–10 cm in thickness and have significant weight, so loss of adhesion here is especially dangerous.

We will discuss the interaction between concrete bases and gypsum materials, as well as the mineral ettringite, in more detail in a separate lesson. For now, let’s move on to the preparation of brick, concrete, and reinforced concrete walls in rooms with high humidity.

Preparation of Brick, Concrete, and Reinforced Concrete Walls in Rooms with High Humidity

Q1

1. Surface cleaning and application of deep‑penetrating primer.
2. Application of cement plaster using installed guide profiles.
3. Leveling plaster with a straightedge.

Q2

1. Surface cleaning and application of deep‑penetrating primer.
2. Application of cement plaster using installed guide profiles.
3. Leveling plaster with a straightedge.
4. Leveling plaster with a trowel.
5. Smoothing.

Q3

1. Surface cleaning and application of deep‑penetrating primer.
2. Application of cement plaster using installed guide profiles.
3. Leveling plaster with a straightedge.
4. Leveling plaster with a trowel.
5. Smoothing.
6. Application of deep‑penetrating primer.
7. Application of a continuous layer of cement putty up to 1 mm.
8. Sanding putty with 120 and 180 grit abrasives.

Q4

1. Surface cleaning and application of deep‑penetrating primer.
2. Application of cement plaster using installed guide profiles.
3. Leveling plaster with a straightedge.
4. Leveling plaster with a trowel.
5. Smoothing.
6. Application of deep‑penetrating primer.
7. Application of a continuous layer of cement putty up to 1 mm.
8. Sanding putty with 120 and 180 grit abrasives.
9. Application of deep‑penetrating primer.
10. Application of a continuous layer of moisture‑resistant polymer putty up to 0.5 mm.
11. Sanding putty with 240 and 320 grit abrasives.

Why Cement Materials Are Used in High‑Humidity Rooms

When preparing brick, concrete, or reinforced concrete walls in rooms with high humidity, the sequence of steps remains the same for all bases. Unlike work in rooms with low or medium humidity, here cement‑based plasters and putties are used. Cement materials withstand moisture well, which is especially important in bathrooms, where wall finishes are exposed not only to high humidity but also to direct contact with water.

The only exception is step 10 when achieving Q4 level. At this stage, a moisture‑resistant polymer putty must be applied. The reason is that cement putties are less elastic, require a thicker minimum layer (from 1 mm), and are much harder to sand due to their high strength. These characteristics limit the precision needed to move from Q3 to Q4. Polymer putty, being more flexible and easier to sand, allows the surface to reach the highest quality level.

Conclusion

The knowledge gained in this lesson develops your ability to “see” the surface more deeply than an ordinary person. You now understand how construction mixes create the foundation for the decorative layer. This is the base without which it is impossible to work confidently, calmly, and professionally with decorative materials.

You have learned the main methods of preparing rough walls made of brick, concrete, and reinforced concrete — from the basic Q1 level to the maximum Q4. In the next lesson, we will examine the second group of mineral bases and analyze their specific features. This will logically continue the material covered and give you a complete picture of base preparation — the very foundation on which the quality of all subsequent decor depends.