Preparing the ceiling for plaster. Anyone can plaster the ceiling with their own hands.

Plastering the ceiling
Grouting the plastered surface

In order to describe as clearly as possible how to plaster a ceiling with your own hands, let’s take as an example small room. For this we will need the following materials:

laser or water level;
rule;
lighthouses;
gypsum plaster;
self-tapping screws with dowel;
gypsum plaster.

Tools for applying plaster.

Before you start plastering, you need to carefully mark and prime the surface.

Marking the ceiling surface and priming it

First you need to correctly mark the ceiling.

Beacons on the ceiling should be placed in the direction of light falling from the window.

This is necessary so that if some error occurs when installing the beacons (most often the average beacon is installed incorrectly), it would not be so noticeable. It is necessary to take into account such subtleties, because when placing beacons across the room, the light falling from the window will reveal such an error.

Scheme for marking a room with beacons.

Depending on the width of the room, beacons are installed. Up to three meters - two rows of beacons are installed, each row is installed at a distance of about 60 cm from the walls. The process of plastering ceilings with your own hands takes place in the following sequence: first plastering middle lane, then two side ones. In rooms with a width of 3 to 5 m, beacons are placed in three rows. If the width of the room is more than 5 m, then there can be four rows, etc.

As an example, we took a room with a width of 3.5 m, so we will need to install three rows of beacons. We install two rows near the walls, retreating about 20 cm from them, and we place the last one along the center of the room, thus as if dividing it in two. In this case, you can begin the plastering process in the direction from the center of the room to its wall. In this case, the length of the rule allows you to do this. The first beacon in each row should be about 2.5 m, slightly less than the length of the rule for plaster. The second one can be any size.

Then you need to note in which places the screws will be screwed in; they are needed to correctly mark the height difference in the room. For your convenience, you can immediately write on the ceiling where each beacon will be located, so as not to re-measure them. After the marks for the screws have been made, use a puncher to make holes in the places of the marks and install dowels into these holes.

The sequence of applying primer layers to the ceiling: 1 – first layer; 2 - second layer; 3 – direction of light rays from the window.

Before you start screwing in the screws, you need to prime the entire ceiling. Primers for carrying out plastering works There are a great variety in construction stores, so choose it in accordance with the surface that you are going to plaster. If the surface is smooth, then a stronger primer is needed, for example betokontakt. When treating the surface, you should not skimp on the primer. After you have completely treated the entire ceiling area, you need to let it dry.

Once the primer has dried, you will need to find the lowest point in the room. To find this point, you can use a laser level; if you don’t have one, then a simple water level will do. To measure with a water level, you need to tie it to a rule and measure starting from the corner of the room, while noting the height level of each section near each hole for the screws. The purpose of these measurements is to find the lowest point where the thinnest layer of plaster will be. If you make a mistake when measuring, then overuse of plaster may occur and the layer will come out very thick. Or at the end of the work you may come up against a ceiling plane on which it will not be possible to apply even the thinnest layer of plaster.

Methods of applying decorative plaster to the ceiling.

When the lowest place is near drilled holes found, screw the screw in there so that it sticks out about 5-7 mm. This thickness is plaster beacon. Since the screw was screwed into the lowest place of our ceiling, other screws will stick out a little more. We take the second screw and screw it in approximately at the same level as the first. We check the horizontal between them using the rule, using a water level we check the second self-tapping screw relative to the first.

Depending on what the level shows, we screw in or unscrew the screw, while not forgetting to check each action with the level. We adjust the following screws in the same way, be sure to check the level between them. To mark using a water level, you will have to spend about 2 hours of your time. With laser, everything is much simpler; the whole process will take about 20 minutes.

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Plastering the ceiling

Rotband plaster has the following features: you cannot apply more than 1.5 cm of plaster, and you cannot apply a second layer either. Such rules exist in European countries. With us, everything is much more prosaic; most often they apply a second layer up to 5 cm thick.

The principle of plastering the ceiling is the same as that of plastering walls, that is, apply plaster to the ceiling and remove excess. You can apply the solution different instruments depending on the thickness of the layer. If the layer thickness is less than 1.5 cm, then it is better to use a steel trowel.

Scheme for applying plaster using a crumb thrower.

You don't need to put it on it a large number of solution and gently spread it over light ceiling movements with pressure. If your layer is more than 1.5 cm, then it is better to work with a spatula. When you mix the solution, you need to remember that a solution that is too thick will not apply well to the ceiling and will fall off under its own weight. Therefore, the solution should be made not very thick so that it sticks to the surface better.

If the solution is thick, so-called bubbles may appear. These are places where the solution did not adhere to the surface of the ceiling; it sagged under its own weight, and thus formed air bubble. Most often, such bubbles appear in the corners. To avoid this, you must first apply a thin layer of plaster, and then apply the main one. The point is that the solution sticks very well to the solution and no voids are formed.

The second layer must be applied before the first dries so that the layers can bond better. If you apply a second layer after the first has dried, cracks may form on the surface of the plaster, and you will have to remove the entire layer so that it does not fall off on its own in the future. And with bubbles it’s even easier, you need to wait until the solution dries and use a spatula to remove the place where it forms down to the very base. And then put new plaster on this place.

It is better to carry out the plastering process with your back to the window, so the light will not disturb you. Removal of excess solution occurs by moving the rule or trowel towards you. The finishing movement, on the contrary, is done on your own, so the light from the window will allow you to see the gaps between the plaster and the rule and quickly respond to possible problems.

After applying plaster to the main areas of the surface, there may be places along the walls where plaster has not yet been applied; you also need to remember to unscrew the screws. They may prevent you from leveling the mortar with the rule, and after grouting they may be visible even under a layer of putty. The holes from them and places along the walls are sealed after the plaster has dried. After this, we remove all the beacons and seal the resulting furrows.

Who said it can't be done high-quality repairs with your own hands? It is possible, but you will have to work hard. Have you decided to plaster the ceiling? Do you think you have enough strength? Then read carefully.

Before you start plastering ceiling slab, we need to stock up on everything necessary materials and tools, as well as carefully study the process technology.

Tools and materials

For work we will need:

primer deep penetration;
gypsum plaster;
plaster lath (beacon 6 mm);
a construction mixer or a drill with a special attachment;
serpyanka (plaster mesh) with a sticky side;
wide plaster mesh (optional);
narrow spatula (for applying the solution);
wide spatula (for leveling the plaster);
Master OK;
rule;
horizontal level;
bath for painting;
roller with extension;
plastic bucket;
protective glasses;
respirator;
gloves;
headdress.

Surface primer

Priming the ceiling is an important part of the job. It is needed for reliable adhesion of the plaster to the ceiling. It is best to use a deep penetration primer, as it provides the highest adhesion strength of the finishing layer to the concrete base. Another plus is that many types of this primer contain additives that prevent the growth of fungus.

Before proceeding directly to the primer, you should clean the ceiling of the old coating, if any (paint, whitewash, falling off plaster, etc.). If the work promises to be dusty, it is advisable to use special glasses and a respirator. They will protect your nose, mouth and eyes from construction waste. Clean the ceiling with a spatula, water and a rag. To remove paint, it is better to use a special metal brush.

After cleaning, the ceiling is washed and left to dry, and also wet cleaning rooms. This is necessary to prevent dust from settling on the primed ceiling.

Having carried out the preparatory work, we proceed to the primer.

We protect all already finished surfaces by covering them securely with film.
We put on gloves and a hat.
Pour the primer into the prepared paint tray.
Dip the roller in primer, get rid of excess moisture using the ribbed part of the bath and coat the ceiling in one direction, leaving no gaps.
We are waiting for the ceiling to dry.
We do the same thing, applying the primer perpendicular to the previous layer.
Washing tools.

If you suddenly drip primer onto the floor or walls, wash them immediately warm water. Otherwise, there will be a stain that will be impossible to get rid of.

Installation of beacons

Beacons are installed to level the ceiling surface in a horizontal plane. Before installing them, check the level to see if there are any sharp changes on the surface of the slab. In this case, you risk using too much plaster.

Before installing the beacons, we prepare the ceiling surface. If there are seams on the slab, glue serpyanka to them.

Using a horizontal level, we determine the upper and lower points of the ceiling and make marks.
According to the marks, we pull the string on the walls.
Draw parallel lines on the ceiling with a pencil. The first line runs 30 cm from the wall. The second is at a distance slightly less than the length of the rule. Using this technology we make markings for required quantity lighthouses.

The best material for the ceiling is gypsum plaster. Beacons are installed with its help.

We put on gloves.
At intervals of 30 cm we apply small layers of plaster to the place where the lighthouse is attached.
We fix the beacon. It will adhere perfectly to gypsum plaster.
Using a level and orientation on the cord, we level the lighthouse by applying plaster and cutting off the remains with a rule.
We install the remaining plaster strips. We make sure that all beacons are in the same horizontal plane.
We are waiting for the plaster to dry and firmly attach the beacons to it. You will have to wait about an hour.

Instructions for plastering the ceiling

Let's start applying the plaster. First, let's prepare a solution.

Pour water into a plastic bucket at the rate of 18 liters per 30 kg of dry mixture.
Pour 6-8 trowels of dry plaster into the water and mix.
Pour the remaining contents of the bag into a bucket and mix thoroughly using a construction mixer or drill with a special attachment.
As a result, we get a homogeneous mixture, let it brew for 5 minutes, and then mix again.

The solution is ready. You can’t add anything else to it, otherwise it will spoil.

Let's start applying the plaster:

Using a small spatula, apply the plaster mixture evenly onto small area ceiling.
We follow the rule along the beacons, removing excess plaster.
We repeat the procedure on the next section, thus plastering the entire ceiling.
After the plaster layer has hardened, fill the remaining sinks on the ceiling with the solution, removing excess mixture with a wide spatula. We wait until the plaster dries.
We repeat the same procedure, applying a layer of plaster perpendicular to the previous one. Let the ceiling dry.

After drying, look to see if there are any plaster particles left on the ceiling. If there are any left, take a spatula at an angle of 45 degrees and cut them off.

Deciding whether we will attach plaster mesh to the entire ceiling. If there are places on the ceiling where the layer thickness exceeds 30 mm, it is recommended to install a mesh. This is done like this:

Apply a thin layer of plaster to the ceiling (it is desirable that the solution be more liquid than when applying the main layer);
We attach the mesh to the solution, leveling it with a wide spatula and making sure that the edges of the two meshes meet;
We do this all over the ceiling and leave it to dry;
Using a wide spatula, apply the penultimate thin layer of liquid plaster, filling possible unevenness and removing excess;
We repeat the same procedure, applying finishing layer perpendicular to the previous one;
After drying, remove the remaining excess plaster with a spatula, holding it at an angle of 45 degrees.

The ceiling is ready for further finishing.

Of course, ceiling structures also take up a little centimeters, depending on the material used. So, the distance between the suspended ceiling and the ceiling surface will be equal to the width of the profile (about 4 centimeters).

Flaws

If you cannot carry out the repairs yourself, then the services of construction and repair companies will significantly empty your wallet.
When plastering ceilings, you can hide no more than 5 cm of level differences. The fact is that for serious errors you will have to spend too much material. But main reason The problem is that a thick layer of mortar can fall off the ceiling, unable to withstand its own weight. In this case, the inhabitants of the house or apartment where repairs are taking place may seriously suffer.
Plastering such a complex surface as a ceiling requires some experience. A beginner can handle installing a cassette or suspended ceiling, but it will be difficult for him to properly cover a large ceiling area with plaster. And for painting you need a perfectly flat area.

Important. For subsequent painting of the ceiling, it is necessary to create a completely flat surface. Only in this case, the end result will be impressive.

Now we come to the main question, how to level the ceiling with plaster? First, you should take a good look at the area and decide whether it is worth plastering at all. The fact is that it is not necessary to proceed with this labor-intensive procedure if the surface unevenness is no more than 5 mm. In this case, you can only cover the ceiling with putty using a spatula and a rule.

We have already talked about a layer of solution that exceeds 5 cm earlier. It is better not to start this idea, which threatens human life and health. And beginners are recommended to plaster the ceiling only with a layer not exceeding 3 centimeters.

Ceiling preparation

A ceiling that has many problems must undergo careful preparation before plastering begins. The entire surface should be well moistened with water. It is better to do this procedure 2-3 times, taking a break between them - 2 hours. This way, it will be easier to remove the old plaster, and there will be much less dust. The old coating must be cleaned down to the very base. In places where the solution is difficult to remove, you can use a hammer drill. Thoroughly clean the seams between the coating from pieces of plaster. After this, all dust and dirt must be removed from the surface using a damp sponge.

Important. If indoors high humidity, and there were traces of fungus or mold on the ceiling, be sure to treat it with an antiseptic primer.

After applying the antiseptic mixture, the ceiling will no longer be attacked by fungus. It is worth noting that using any product containing chlorine can only destroy mold. However, after treating the surface with antiseptic primer, the fungus will never appear again. Therefore, it is better to carry out this operation and not skimp on trifles.

Now you need to coat the ceiling with a deep penetration primer. Thanks to it, the concrete layer will be well fixed, and the adhesion between the base and the plaster will improve.

Blend selection

Plastering the ceiling can be done using cement-lime mixtures. Can also be used for ceilings modern plasters on a gypsum basis. It is with the help of this composition that you can easily bring the ceiling to ideal condition. Gypsum coating can withstand a small percentage of building shrinkage. Under the same conditions, the cement-lime finish may crack.

Gypsum plaster has excellent adhesion to concrete surface It is worth paying attention to the fact that basically ceiling It has concrete base. In this case, the mortar can simply be spread on the surface, and not just thrown on, as is the case with cement-lime mortar. That's why even a beginner can handle the gypsum mixture.

Using beacons

For more quality leveling Ceilings are used to install beacons. This makes it possible to eliminate even significant differences existing on the surface. For this laser level determine the lowest point of the ceiling. Having retreated 10 mm below the point, a section of plaster is beaten off and profiles are installed.

In order to secure the beacons evenly, you need to hammer the nails along the line and pull the fishing line over them. Using the line as a guide, we make several piles of mortar along the line and press the profile into them. The distance between them should be less than the rule you will be working with. More details can be seen in the video. With the help of beacons you will never be mistaken with the height of the solution layer.

Advice. Working with a short rule is much easier. The long rule makes it possible to install beacons at a greater distance from each other. In this case, the surface can be made more even.

Using a spatula, the plaster mixture is applied to the ceiling in such a way as to hide the beacons. By moving the rule in a zigzag manner, excess plaster is removed. According to the technology for applying the mixture to the ceiling, a layer should be applied no higher than 2 cm. If unevenness still appears on the surface, apply a second layer of solution only after the first layer has completely dried.

Important: If the ceiling is plastered in two layers, then a plaster mesh is installed between the beacons immediately after treating the surface with the first layer. In this case, the plaster will not crack.

Finishing

The last operation to level the ceiling is putty. If used for surface treatment gypsum mixture, then you can immediately finish the ceiling with the final putty.

If this is your first time repairing the ceiling, it is better to apply two layers of putty, but in a thin layer. Two thin layers will give a smoother surface than one thick one. In this case, after applying the first layer, you need to wait until it dries. And only after that proceed to applying the next layer of solution. This is done using a wide spatula.

Now you can start sanding the ceiling surface. To do this, use a grater on which a sanding mesh is applied. if you have Sander, with its help you will cope with this operation faster. When sanding the ceiling, be sure to use a respirator and goggles.

Solution to use textured plaster for finishing the ceiling can be assessed ambiguously. For example, for the kitchen this option is not acceptable at all. The fact is that removing dust from such a finish will not be easy. In this case, you can apply textured plaster on polymer based. If you are preparing the ceiling for painting, it is better to re-prime it. In this case, less paint will be used, and the ceiling will last longer.

The first impression of the interior is formed based on the ceiling. This is what people look at immediately after entering your home. Today there are many options for surface design - decoration, hanging or stretch ceiling etc., but plaster still remains relevant.

Ceiling leveling

First of all, the ceiling must be inspected for any irregularities. The number and size of dents, holes, cracks and humps should be determined. To ensure that these defects do not eventually manifest themselves, it is necessary to level the surface. Finishing can be completely different - painting, putty or any other treatment.

Alignment methods

Plastering ceilings with your own hands should be carried out in compliance with the recommendations of professionals. So, builders share two methods of leveling - wet and dry. The first refers to the use of various mixtures and solutions with which the ceiling is leveled. The second way is to use various slabs(plasterboard, PVC and others).

How to plaster the ceiling with your own hands in this case? It all depends on personal preference, but there are also rules according to which you can assess the reality of alignment in one way or another. If differences in height on the ceiling exceed 5 cm, then it is better to choose drywall to level such a surface. Plaster of such thickness poses a serious danger, since in case of some violations during its application it is quite possible that the layers will peel off, which can cause bodily harm to residents.

If the ceiling does not have such strong unevenness, then plaster can be used to level the surface. At the same time, to obtain good quality When painting, the surface does not have to be flat, but instead should be smooth. But, whatever one may say, surface evenness is one of the aspects of aesthetic beauty.

Materials used

Plastering the ceiling with your own hands is possible using mixtures based on cement or gypsum. Gypsum plasters are considered more environmentally friendly; they dry faster and generate less dust. Cement mixtures are much cheaper. Due to the difference in performance properties, these two types of plasters are used for various works. Thus, gypsum is recommended to be used for interior decoration, cement - for external.

How to plaster a ceiling with your own hands?

Plastering ceilings with your own hands requires the following tools:

container for diluting plaster. The container must be large;
drill with mixing attachment building mixtures. Power not less than 600 W;
trowel and set of spatulas;
usually a grater;
brush and roller for applying primer.

If you don't know what some instruments look like, you can find photos of them on the Internet.

Preparatory work

Before you begin, you need to bring it into proper condition. The surface must be specially prepared. To do this, remove the layer old plaster or paint with a sharp spatula. If necessary, the tool can be sharpened during this procedure.

If the ceiling was covered with lime, then it is moistened with ordinary water. To make it easier to remove water-based paint from the surface, add a little iodine to the water. Water-dispersed paints are removed using special removers.

In addition to paint, all poorly adhering pieces of plaster are removed, as well as, if possible, all irregularities. In addition, it is necessary to get rid of the plaster at the joints of the slabs. To do this, use a hammer or spatula. Remove only the plaster that chips off without effort or has already moved away from the slab.

IN mandatory the surface is checked for the presence of fungus, especially if the room has humidity above normal. To remove it, infected areas can be treated copper sulfate. If the fungus has affected a large area, then it is necessary to chop off upper layer surface, and treat the area itself with a burner flame.

After all of the above procedures have been completed and the surface itself has been cleaned, it is treated with a deep penetration primer. Smooth areas of the ceiling are treated with a roller, the rest with a brush.

Plaster and putty

To avoid confusion, it is necessary to distinguish between these two similar concepts. Putty is the final stage of work immediately before finishing the ceiling. The thickness of the resulting coating should not exceed 3 mm. Performed using fine mixture and plaster.

Plastering is carried out using coarse mixtures based on gypsum or cement. The purpose of this treatment is to level the surface. First, the surfaces are leveled with plaster and only then they are covered with putty.

Preparation of mixtures and their application

This procedure is quite simple if you follow the manufacturer's recommendations. General rules, regardless of the type of mixture:

water is poured into the dilution container;
the dry mixture is added there in the proportions specified in the instructions;
the resulting substance is mixed construction mixer or a drill with a special attachment;
after obtaining the required density, the mixture settles;
after that it is mixed again.

The mixture is applied to the ceiling with a spatula. In this case, a plastic spatula is used for application, and a metal spatula is used for leveling. You can also use a trowel - this is a special trowel with a curved handle. After the plaster is applied to the ceiling, it is leveled.

Plastering the ceiling on beacons, details in the video:

Ceiling leveling options

Despite its simplicity, the task of leveling the ceiling with plaster can be divided into several independent operations. The fact is that all ceilings are different, and therefore the problem of surface treatment in each individual case is unique in its own way.

Fairly flat ceiling

In such a situation, after the primer has been applied, small holes and cracks are sealed. To do this, put them in with a spatula. ready mixture and level. In this case, different situations may arise. If the ceiling is not even, then general plaster will have to be applied over the entire ceiling.

If the defects are large and it is necessary to use a large amount of plaster, then laying on a grid is used. To do this, take a painting mesh or, in other words, a sickle net and attach it to the ceiling. The material is very similar to gauze, but is essentially a reinforcing mesh. After fixing it, a layer of plaster is applied. This serpyanka is used when the thickness of the plaster layer exceeds 10 mm.

Wooden ceiling

Such surfaces require special preparation. Thin layer plaster simply cannot level the ceiling. In addition, if people are expected to move on the second floor or attic, the floor will sag, which will cause the plaster to peel off. Therefore, it is applied over a grid or shingles are used.

They stuff it in two layers, which are placed at an angle:

the first layer consists of thin and uneven shingles up to 5 mm thick. It is nailed at an angle of 45 degrees, with a step between the slats of 5 cm;
the second is stuffed from slats with a flat front surface at an angle of 90 degrees to the first row. Thus, cells measuring 5-10 cm are formed on the ceiling.

Renovating any room, be it residential or office, starts from the ceiling. Regardless of what finishing is provided for in the design project: whitewashing, painting or pasting decorative panels, the surface to be treated must be prepared according to all the rules.

In short, how can you smooth out the flow?

Comparing various methods leveling the ceiling, you should find out what is the fundamental difference between plaster and putty? Both options for eliminating nervousness refer to the “wet” method, which is based on the use of various building mixtures and compositions. Ceiling leveling is considered “dry”, but such a radical solution to the problem is resorted to as a last resort.

Surface filling is performed as follows: finishing before painting or wallpapering. The layer of material cannot exceed 3-4 mm. The peculiarity of this coating is that its use is permissible on almost flat surfaces with minor defects, subtle cracks and small irregularities, since a finely dispersed putty mixture is not able to tighten and hide more significant problems.

Plaster screeding is carried out on surfaces with height differences of up to 45-50 mm. Thanks to the coarse particles, the mixture easily copes with deep cracks and seams between slabs and floors. However, if the differences exceed 5 cm, use plaster mixtures not recommended - too thick a layer of material is not only aesthetically unattractive, but also dangerous due to the likelihood of cracking and peeling of the plaster from the ceiling, which can pose a potential health hazard and result in injury. In such situations optimal solution there will be installation of frame ceiling structures using slabs or suspended ceilings made of modern materials.

When choosing one or another finishing method, you should take into account all the advantages and disadvantages of the material.

The advantages of plaster are in the following aspects:

The disadvantages of plaster mixtures are as follows:

there is a limit on maximum thickness plaster layer - experts do not recommend exceeding a threshold of 5 cm - when large differences Leveling with this material is impractical and is characterized by high consumption mixtures;
if it is not possible to do the work yourself, the services of professionals will cost a significant amount, plus take into account the cost of the material itself;
Leveling the ceiling with plaster mixtures requires certain skills in working with materials and tools, and the process itself can take a very long time, since the main task is to make the surface smooth and even.

Prices for popular types of plaster

Plaster

To plaster the ceiling yourself, you will need the following materials:

Step 1. Surface preparation

The preparatory stage has great value even if we are talking about a new building. Ideally, the ceiling should be cleared down to the concrete slab.

Traces of mold, mildew and rust stains should be removed with a wet sponge, then wash the ceiling area special compounds. Old and peeling layer of plaster and other building materials needs to be removed.

Even if the coating looks durable and without noticeable signs of wear, experts recommend removing it. Firstly, sooner or later cracks may form on the ceiling, and secondly, such layering will steal extra centimeters of space.

The most suitable tool for this work is a narrow spatula. If layer finishing materials It is difficult to remove, you can try to “tap” the treated area with a rubber hammer or use an electromechanical drill with a special brush attachment. It is very important to remember to protect your eyes, head and respiratory tract from construction dust.

It is useless to wash away the plaster with various solutions, since after such treatment a thin, smooth and difficult to remove layer remains on the ceiling surface, which will interfere with the work. quality work due to low adhesion, which can cause detachments and cracks in the applied layer of plaster.

Relatively flat ceilings

The ceiling is plastered with two, less often three layers of the mixture. If there are minimal surface defects, it is allowed to apply plaster to selected areas, followed by leveling the material, but craftsmen recommend applying at least one solid layer to the entire surface. If there are numerous irregularities and the expected layer of plaster will exceed 10 mm, before starting work you need to attach a painting mesh to the ceiling - this will protect the coating from cracks and give greater strength.

Ceilings with large unevenness

If the surface differences are significant and amount to more than 2 cm, then leveling is best done using. Their installation is a responsible and important stage.

Planned minimum thickness plaster layer - depends only on the specific conditions of the room being finished and the wishes of the owners. As a rule, a layer less than 5 mm is not applied when plastering.
The amount of difference in ceiling height that needs to be eliminated by plastering.
Master's qualification level. A professional will waste no more than 5% of the solution, but for a beginner, at first, even 15% of the solution may not be enough.

The resulting value will initially be expressed in kilograms. But dry plaster mixtures are sold in paper bags of 25 or 30 kilograms, and purchasing an open bag is great stupidity, since no one can guarantee the quality of the solution. This means that one way or another you will have to round up the amount of purchased composition up to the whole number of bags. This supply will still not be superfluous - all the repairs are still ahead! This is also taken into account by the calculation program.