Do walls need to be primed before plastering?

Plastering walls during the renovation process is one of its most important stages. How well you do it depends on the durability, strength and aesthetic appearance of the finish coating: wallpaper, paint or tiles. Sometimes the plaster itself begins to crack and fall off. Pre-coating the walls with a primer can save you a lot of problems and wasted time and money.

Is it really necessary to prime the walls and is it possible to do without it - a question that interests many people who are starting repairs. Can be distinguished several important functions that the primer performs:

• strengthens the crumbling and porous surface of the base of the walls;
• improves the adhesion of the plaster and the previous layer;
• reduces the risk of moisture ingress from the wall to the decorative layer, that is, acts as a waterproofing;
• the primer mixes contain special additives that provide an antiseptic effect (resist fungi and mold, which is important in wet rooms) and increase the fire-resistant properties of the plaster;

• improves the quality of the surface, since during its application, small particles and construction dust are removed from the base;
• any formulations applied to the primer lay down more evenly;
• protects the final finish from various stains that can appear from the walls.

From all of the above, we can conclude that priming is required before plastering.

The primer can be subdivided according to different parameters. One of them is the impact feature. The mixtures differ in composition, and each additional ingredient affects certain properties of the final product:

• Adhesive composition used for better contact with materials that do not absorb moisture well. These include plastic, glass, tiles, or metals. Dense coatings are not able to adhere to the plaster on their own.

• Deep penetrating mixture... It must be used for porous substrates such as concrete, drywall, brick, areas of plastered walls. The composition increases the strength of the wall, saves the consumption of plaster by reducing its absorption.

• Insulating compounds... The need for their use arises when there are visual color defects on the base of the walls: various spots, rust and paint.

• Antifungal and anti-mold compounds. First of all, their use is justified in bathrooms, lavatories or kitchens and other rooms with high humidity. They prevent wall damage from microorganisms and guarantee a healthy room environment.
• Universal primer combines several types to improve the quality of the base and facilitate the application of plaster on it.

The compositions of the primers are different, in this regard, several types can be distinguished:

• Acrylic compositions. It is a versatile primer for a wide range of surfaces and many finishes, including emulsion paints. The ecological properties of acrylic determine the popularity of its application and give advantages to the composition: it dries quickly, has no odor, and increases the adhesion ability.Such mixtures are not suitable only for metal substrates: they can contribute to the appearance of rust.

• Alkyd primers are versatile enough to be applied on different types of substrates. The only exceptions are walls made of porous materials with increased absorbency: concrete, brick, drywall, etc. If the mixture contains phosphates, then it should be used mainly for coating with acrylic paint.

• PVA soils. Many people try to prepare such solutions themselves. They have a number of disadvantages: they provide insufficient adhesion, they can contribute to the detachment of the plaster if the proportions of the mix are violated, and they can cause yellow spots on the final finish.

• Mineral solutions. They are intended for porous substrates: gypsum, concrete, walls made of gas silicate blocks, bricks or covered with a layer of plaster.

• Polystyrene primer. It is used for wooden and plastered walls. But indoors, such a composition cannot be used because of its toxicity.

To improve the properties, components that form a film layer or accelerate the drying of the surface can be added to various types of primer mixtures. In the characteristics of the primer, the type of substrate is often mentioned. Therefore, it is appropriate to separate the primer materials for:

• wood;
• metal;
• glass;
• plastics;
• mineral bases.

The optimum choice of primer is dictated by differences in substrate properties. For each surface, it is necessary to select the type of mixture that will prepare it as much as possible for the application of plaster and ensure the durability of such a coating.

Several groups of wall surfaces can be distinguished:

• Metal surface. In an apartment you are unlikely to find this type of material, but in a private house it can be gates, garage doors, and various partitions. If you need to plaster them, it is worth using a rustproof primer.

• Hydrophobic types of bases. This group includes glass, plastic, laminate, tiles. Before applying the plaster, they must be treated to improve the adhesion of dense and smooth materials to the next layer. To form a film on the surface, you can use primer mixtures with the addition of resins or PVA. It will then be much easier to apply paint or plaster.

• Wooden surfaces have two significant drawbacks: they burn easily and are susceptible to various microorganisms. This applies not only to natural wood, but also chipboard, wood slabs and blocks of pressed shavings. The correct primer mix will increase the safety of the coatings and protect against mold in the event of high humidity.

• Loose and porous surfaces. This group includes walls made of foam blocks, aerated concrete, brick, concrete. The structure of the materials will encourage excessive absorption of moisture-containing mixtures into the surface of the walls. Therefore, on brick bases or walls, the basis of which is a gas block, it is customary to apply a primer that forms a special protective film.

For the most part, before plastering walls, you need to solve only two problems: how to strengthen the surface and ensure the durability of a coating with a smooth base. In the first case, deep penetration primer mixtures form a film, which, when heated, begins to emit a characteristic odor. Among mixtures for smooth surfaces, concrete contact containing adhesive additives is widespread.

After the first layer, you will see the quality of the whitewash on the surface. If nothing is damaged, you can use special whitewash compounds. In case of defects, it is best to remove the entire chalk layer.

If you are not particularly versed in building materials, it is worth examining the products of the brands:

• Knauf. This is a German manufacturer that guarantees the appropriate quality and has been improving its technologies for the manufacture of building materials since the first half of the last century. The line of primers includes deep penetration compounds, universal acrylic, concrete contact and even solutions for decorative plaster.
• Tikkurila... Finnish leader in the sale of paints and finishing materials, known all over the world. The choice of different primers will allow you to choose the most suitable mixture for your specific problem.

• Ceresit Is another high-quality German brand produced by one of the world leaders in the production of various materials Henkel. The company is constantly applying the latest technologies, expanding the range and working on a pricing policy. The cost of products remains acceptable due to the manufacture in Russia. The most popular are four types of soil: deep penetration, under decorative plaster, concrete contact (can withstand temperatures of -40? C) and antifungal.
• "Prospectors" Is a Russian company that has been developing various building materials for over 20 years. A tempting price tag, combined with decent quality, according to customer reviews and a wide range of primers make it a serious competitor to foreign counterparts.

• Bergauf - the result of investing funds from Germany in order to create German-level dry mix plants in Russia. The history of the brand does not have two decades, but it has already won the trust of buyers. The range includes 4 product options: deep penetration primer, adhesive primer, universal and for external and internal surfaces (frost-resistant).

Below are a few guidelines that can help you avoid common mistakes when working with primers and in some cases save time and budget:

• Any substrate must be carefully prepared before priming. All the bumps of cement are removed from the brick wall. The concrete is dedusted and leveled. Wooden bases are cleaned of dirt and dust. If a large layer of plaster is required, fill in a mesh of thin strips for greater adhesion.

• Sometimes you can use other types of solutions instead of a primer. If you mix PVA and sand to a state of light homogeneous slurry and apply on a cement base, you can safely lay tiles on such a coating. It is better to refuse the use of water-based paints instead of primers. In this case, the adhesion properties will be low, and the moisture protective layer will be ineffective. Instead of saving, you get poor strength and high plaster consumption.

• When working with wooden walls and ceilings, it is definitely better to resort to store products. At home, you will not be able to find all the necessary anti-mildew and strengthening additives in the right proportion, and the risk of deterioration of the coating will be great.

• In the process of mixing the primer composition, strictly follow the instructions on the package. This will ensure the quality and durability of the topcoat.
• If the surface is very loose and porous, the consumption of the mixture may increase in relation to that specified by the manufacturer. Therefore, it is best to always take a primer with a small margin.

• Do not use a mixture of primers from different manufacturers. This will violate their declared qualities and functions.
• In conditions where it is necessary to choose a certain shade for covering the wall, you can use special formulations containing a colored pigment. Both the primer and the color scheme are best purchased from one manufacturer. This will provide better communication and reliable results.

You can learn more about the primer in the next video.