Professional finishers are confident in the need for priming the surface before performing any work on applying the finish coating, but most owners who make repairs on their own doubt that this procedure is mandatory. So why do we need a primer before painting the walls, applying leveling solutions and before gluing the surface with wallpaper?
Indeed, the acquisition of soil and surface treatment makes it more expensive to finish the apartment, but the positive results of such preparation significantly overlap the amount of additional costs. The main task of applying primers is to level the surface before performing work. Concrete, gypsum, wood - any materials have a porous structure and defects invisible to the naked eye that interfere with strong adhesion.
The soil, penetrating deeply (up to 10 mm) into the base, smoothes out all small cracks, bumps and chips, removes dust, forming a thin and even film on the surface. It is thanks to this film that more uniform coloring occurs, wallpaper gluing is much easier, and plaster mortars get better adhesion to the surface of the base.
In addition to the main task of leveling the base, primers perform additional useful functions: increase the service life of the coating, provide antiseptic protection of the base, act as a surface treatment against insects and rodents.
The primer provides reliable adhesion of the wall with paint, plaster, glue for ceramic tiles or adhesive for wallpaper, blocking the path of moisture through the concrete layer. It is due to the penetration of vapors and moisture through the concrete base that premature detachment of glue and plaster occurs, which leads to damage to the finish coating (the tile falls off, the wallpaper leaves the wall, the paint peels off, the plaster crackes).
What causes the need for priming
The mandatory application of soil in various situations needs to be considered in more detail.
Before wallpapering
First you need to figure out why you need to primer the walls before wallpapering. To obtain an even coating of the walls with rolled materials, the base should be carefully prepared. Usually, finishers fix problems (chips, cracks), putty the surface, sand it, and then paste the wallpaper on a level base.
The adhesive is quickly absorbed into the porous surface of the wall, after which there may appear places where the wallpaper does not fit snugly to the base, after which peeling of the trellis begins from these areas.
Avoid marriage in the work will allow coating the surface of the wall with a primer. Putty is impregnated with soil and a thin film forms on the surface, which will not allow the glue to dry prematurely. Thus, high-quality adhesion of the putty base, glue and rolled material is ensured.
But before embarking on puttying, experienced builders recommend treating the surface with special impregnation. But why prime the walls before puttying? It turns out that one impregnation before gluing is not enough, since problems often arise at the place where the putty layer comes into contact with the concrete base:
- moisture penetrating through the pores in the concrete does not allow to obtain high-quality adhesion of the putty and base;
- in case of violation of the humidity regime, the putty will exfoliate from the unprocessed soil wall, together with the wallpaper.
Therefore, when preparing the base for gluing, you have to do a soil treatment twice: before filling and after leveling the wall.
Before plastering
In case of large vertical deviations of the base, it is recommended to use plaster solutions to eliminate problems, but when applying the working mixture, moisture is absorbed from the solution into the base, which leads to uneven drying of the plaster layer and the appearance of cracks.
This can only be avoided by applying soil to the base. Such preparation allows you to:
- increase the humidity of the base, which will allow the hydration of the stucco mortar to pass through without interference;
- increase the adhesion of the solution and base;
- eliminate surface dusting;
- reduce the consumption of plaster mixture.
When choosing a primer for plaster, you must carefully study the instructions for use. So, the most popular “Concrete Contact” impregnation is perfect for the subsequent application of gypsum mortars and GCR treatment, but other types of soil solutions will be required to work with cement-sand mixtures.
Why prime walls before painting
The positive aspects of preparing the walls with soil include:Improving the adhesion of the colorful composition with the base.Strengthening the base.The ability of the soil to level the wall for painting.Elimination of small particles of dirt and dust from the surface of the base.Save paint.The treated surface absorbs any type of paint less (enamel, water-based, oil), which saves up to 20% of the material. The cost of impregnation is much less than the savings.This effect is achieved for the following reasons:significantly reduces the porosity of the base;to obtain uniform staining, a thinner layer of paint is required;high-quality coating is obtained even when applying a less concentrated paint composition.We have been preparing the surface for painting at all times, but before, we used heavily diluted main paint for the ground, while now special formulations with higher characteristics are used, but, in the absence of special solutions, you can act the old way - dilute the paint in the ratio for impregnation 1 to 4.
Should walls be primed after puttying
Puttying the base is required to create a flat and smooth surface for further painting or gluing. Scrupulously carried out work with subsequent processing with sandpaper allows you to achieve an acceptable result, but it still fails to remove the tiniest flaws. Often such small defects appear only after the topcoat has been applied.
If the primed walls are pre-painted with a primer, such defects are eliminated, fine dust is removed, and the surface becomes much more suitable for further processing.
Do I need to prime the wall in front of liquid wallpaper
Indeed, why do we need a wall primer for liquid type wallpaper, when it seems that only a level surface is enough to work? It should be remembered that when liquid gets on an unprimed surface, moisture is absorbed by the base, which disrupts the process of forming the finish coating.
As a result, the solution sets unevenly and the material peels off the wall, the color scheme and texture are violated. If you prepare the surface by impregnation of deep penetration, problems can be avoided.
Why prime the wall after removing old wallpaper
When performing finishing work on their own, many apartment owners cannot decide on the question: why should the walls be primed before wallpapering, when the surface, as a result of dismantling the old material, looks quite even and neat?
The answer depends on the method of dismantling the coating and the quality of the actions taken. If the coating was removed without using a spatula, using special solutions, and the surface of the wall was already puttied and treated with soil, applying a new layer of impregnation is not necessary. It is only necessary to remove the self-tapping screws or nails, mask the holes with putty and prime these places and then glue a new coating.
If tools were used during dismantling and the foundation turned out to be damaged, additional leveling with putty mortars and re-treatment with primer will be required. Otherwise, a reliable adhesion of the adhesive composition to the surface of the base will not be ensured and the life of the wallpaper coating will be greatly reduced.