The main purpose of plaster is to prepare surfaces for finishing, that is, to eliminate defects and level the walls. In addition, the plaster mix can act as a decorative coating, depending on the components and application method. How to prepare a solution for plastering walls, how to calculate its amount and apply it correctly, as well as some of the nuances of this process, will be discussed.
How to prepare a solution for plastering walls
Any plaster mortar consists of three main components - binder, water and filler. Cement, clay, lime and gypsum act as a binder, and they are often combined with each other in various proportions.
The filler is most often ordinary sand, but in ready-made factory mixes, it can be replaced with quartz and perlite sand, marble and granite flour, stone chips. Additionally, the plaster mix includes modifying additives - coloring pigments, plasticizers and others.
Types and composition of solutions for plaster
Depending on the type of binder, several types of plaster compositions are distinguished:
Types of plasters and their application
Mixtures with two or three binding components are called complex. In addition to the composition, the ratio of the components also plays an important role - based on this, the solutions are divided into oily, lean and normal.
A solution with a predominance of an astringent component is considered fat. During the drying process, such plaster shrinks and cracks, as a result, the walls must be re-treated. It is not difficult to determine the fat content of the working mixture: when stirring, it sticks to the trowel, remains on the walls of the container in a thick layer.
If there is an excess of filler in the mixture, this is a lean solution. It is almost not subject to shrinkage, does not crack after drying, but adheres poorly to the surface and has too low strength.
It is enough to lightly hit the wall to make the plaster fall off. With stirring, the lean solution easily slides off the trowel, leaving almost no trace.
"Oily" and "skinny" plaster, which is better
Normal mortar is moderately plastic, it is easy to interfere, and if collect a little mass on a trowel and let it slide, a thin uniform layer will remain on the surface. It is this composition that provides maximum adhesion to the treated surface and creates a durable, reliable coating.
| Moisture- and frost-resistant, does not shrink, perfectly tolerates weathering. |
Can be applied in layers up to 30 mm without reinforcement.
Solution proportions: 0.16-0.2 l of water per 1 kg of dry mix.
Consumption of mortar with a layer thickness of 5 mm is 6-8 kg / m2.
Pot life of the finished solution is 2 hours.
Packaged in bags of 25 kg.
|From 280 rub.|
OSNOVIT Flywell cement plaster
| Frost-resistant, easy to apply, can used for exterior and interior walls. The proportions of the solution: 0. |
3-0.42 l of water per 1 kg of the mixture.
With a layer thickness of 5 mm, the consumption is 9-10 kg / m2.
Pot life 3 hours.
Packing - 25 kg bag.
|From 240 rub.|
Weber Vetonit cement plaster
| Possesses increased resistance to low temperatures, moisture resistant, very flexible and easy to apply. The proportions for mixing the solution are 1 liter of water per 4 kg of the mixture. |
Consumption for a thickness of 2 mm - 2.5 kg / m2.
The pot life of the solution is 3 hours.
Drying period from 2 to 7 days.
|From 360 rub.|
Cement plaster "Prospectors"
| Waterproof, plastic, lightweight application. Forms a durable coating that is not prone to cracking and shrinkage. |
Mixing ratio: 0.26-0.28 l of water per 1 kg of mixture.
Solution consumption - up to 2 kg / m2.
The pot life of the solution is 1.
Packaged in bags of 25 kg.
|From 188 rub.|
Decorative plaster UNIS Fur Coat-Decor
| The base is white cement, filler - marble chips. It is resistant to moisture, low temperatures, does not shrink, and is easy to apply. |
Mixing ratio: 0.18-0.2 l / kg.
The pot life of the solution is 1 hour.
Packaged in bags of 25 kg.
|From 423 rub.|
Knauf Diamant decorative plaster
| Color mixture on a cement basis, filler - quartz sand. It has water-repellent properties, tolerates low temperatures well, does not fade for a long time. |
Mixing ratio: 7.5 l of water per 25 kg of mix.
The pot life of the solution is 1.5 hours.
Packaged in bags of 25 kg.
|From 340 rub.|
In the absence of experience in plastering, it is recommended to choose ready-made mixtures - so you will be sure of the correct ratio of components.
Each type of mortar has its own characteristics that must be taken into account when choosing a plaster composition for finishing the facade.
|Type of mixture||Characteristics||Component ratio|
|Suitable for both outdoor and indoor surfaces. Differs in strength, good moisture resistance, easy to apply. The finished solution should be consumed within an hour.When processing the facade, the cement mortar is usually applied in 3 layers, and the proportions for each batch differ|| 1 layer - 1 part of cement and 3-4 parts of sand.
2nd layer - 1 part cement and 2-3 parts sand.
3rd layer - 1 part of cement and 1.5-2 parts of sand.
|Adding lime to increase the adhesive properties of plaster and extend the setting time up to 48 hours. When kneading, not lime itself is used, but lime dough, which is prepared in advance|| 1 layer - 1 part of cement, 0.
4 parts of lime and 3-5 parts of sand.
2nd layer - lime and cement in 1 part, 2.5-3 parts of sand.
3rd layer - 1 part of cement, 1.5 parts of lime and 3-4 parts of sand.
|Pure lime mixture for facade plastering almost not applicable, except for adobe houses. Such a coating does not have the required strength and does not tolerate excessive moisture, but it has high adhesion and antiseptic properties||1 part of lime and 3 parts of sand.|
|Such solutions are used, as a rule, for plastering walls from adobe and wood. They are considered the cheapest, environmentally friendly, ready-made solution suitable for use for several days. But at the same time, clay plaster is too fragile, afraid of moisture, damaged by fungi and insects|| 1 part of clay and 3-5 parts of sand.
|Clay and cement plaster has good strength , tolerates slight increases in humidity, does not require large preparation costs. The use time of the ready-made mortar is reduced to 1-2 hours||1 part cement, 4 parts clay and 6 parts sand.|
|This mixture is very plastic, easily adheres to any surfaces, after drying, forms a durable coating with antifungal properties. For facades, it is used in areas with a dry climate, since it has a low moisture resistance. The finished solution should be consumed within 3 hours|| 1 part of lime and clay, 5 parts of sand.
The indicated proportions may vary slightly depending on the moisture content of the sand, the viscosity of the clay and lime paste, and the air temperature. Sand for kneading must be sieved to remove foreign particles. The clay should also be clean, free from grass residues, stones or dirt. All this reduces the quality of the plaster. Ready-made mixtures have a balanced composition; you do not need to add anything but water to them.
The proportions of the dry mix and water are always indicated on the package, so read the instructions before preparing the solution.
Before proceeding directly to the batch, you need to calculate the required amount of mortar.As you know, an unused storage solution is unusable, and it remains only to throw it away, which means that some of the money will be wasted. Let's take a closer look at how to avoid unnecessary costs.
The most difficult calculation is the curvature of the walls.
It is impossible to achieve a perfectly flat surface when building a house, and it is good if the deviations do not exceed 10 mm. But, as practice shows, very often the differences are from 1 to 5 cm, and in some cases even more. When plastering the entire house, calculations must be performed for each wall separately. First you need to determine the average thickness of the plaster layer.
The surface of the wall is thoroughly cleaned from the old finish, all noticeable bumps are knocked down, the influx of mortar, if necessary, clean the seams.
Deep recesses and cracks in the wall are sealed separately with cement mortar and allowed to dry well.
Step 2. Next, you need plaster beacons, which are thin metal slats with perforation. Their thickness is 6 and 10 mm.
In a small container, alabaster is diluted with water to a thick slurry, then a level is applied to the wall, the vertical is determined and along this line, the solution is at 3-4 points.
How to breed alabaster
Apply a beacon, pressing it into the solution, and check its location with a level. If necessary, press in more or add alabaster. In the same way, other beacons are attached with a step of 1.5 meters along the wall.
Plaster beacon fixed with alabaster
Some builders use special beacon fasteners with dowels instead of mortar, but for this it will be necessary to first make a marking on the wall, and then drill along the lines of the hole. It is easier and faster to work with the solution.
Method of installing plaster beacons
Step 3. Measure the width of the gaps between the wall and the beacons , and then all are summed up and divided by the number of beacons.
Pay attention to the gap between the beacon and the wall
For example, at one point the gap is 2 cm, in the other 3.
5 cm , in the third place generally 5 cm. The more measurements are taken, the more accurate the result will be, therefore measure the deviations under each beacon at several points. Let's say the total is 30 cm, and there are 10 beacons installed. We divide 30 by 10 and we get 3 cm - this is the average thickness of the plaster layer required to calculate the amount of mortar.
Now let's find out the total volume of the plaster mixture: for this we multiply the surface area by the layer thickness. For example, wall width 4.5 m, height 2.5 m, thickness of the plaster layer - 30 mm (0.03 m).
5x2.5x0.03 = 0.3375 m3
Round and get about 340 liters of solution. At a ratio of 1: 3, the volume of cement is approximately 112 liters, or 0.
1125 m3.The average bulk density of cement is 1500 kg / m3, therefore, multiplying the volume by the density indicator, we find out the approximate weight of the material: 0.1125x1500 = 168.75 kg.
Since cement is packed in bags of 50 and 25 kg, you will need to buy 3 large bags and 1 small, or 7 bags of 25 kg.
Similarly, the weight of sand, gypsum, lime and other materials is calculated.
Cement in bags
When using factory mixes, calculations are easier. The packaging indicates the consumption of the composition per square meter at a certain layer thickness. If this thickness matches the one that you got, you just need to multiply the specified consumption by the area of the working surface. If it does not match, multiply the consumption by the area and by the layer thickness.
Lime plaster, bag 35-40 kg
For example: on the packaging of the mixture "Weber Vetonit" consumption is 2.5 kg / m2 with an application thickness of 2 mm. Our design thickness is 30 mm, that is, 15 times more. We calculate how much mixture is needed per 1 square meter:
2.5x15 = 37.
5 kg / m2
Let's say the wall area is 10 m2, then 375 is needed for plaster kg (37.5x10). The standard packing is 20 kg, so we divide 375 by 20 and get 18.75 bags. This means that you need to buy 19 bags of mix for plastering.
Cement plaster is considered the most optimal option for facade finishing. Most often, a simple cement-sand mortar is used, a little less often with the addition of lime or clay. A container is needed for mixing: it can be a special wide box or a trough, and if the volume of work is large, then it is better to take a concrete mixer.
Trough for mixing plaster
Additionally, you will need a shovel and a measuring bucket.
Consider the step-by-step preparation of a solution for three-layer plaster application.
The builders call the first layer spraying or spraying. The consistency of the mortar should be slightly watery in order to easily fill all the pores on the wall surface. Application thickness does not exceed 4 mm. The proportions are given for the preparation of a solution from one bag of cement (25 kg). It is recommended to use cement of the M400 and M500 brands.
Step 1. 6 buckets of sifted sand (bucket 10 l) are poured into the container, cement is poured on top.
Dry sand and cement
Mix everything well with a shovel.
Mixing the ingredients
Step 2. Pour in 15 liters of water and begin to stir intensively, breaking the formed lumps .
.. The mass should become homogeneous.
Step 3. Add another bucket of water and mix the solution as thoroughly as possible to remove even the smallest lumps.
After that, you can start applying the plaster.
The priming layer is applied after the spray has set, but before it is completely cured. The application thickness should not exceed 15 mm if the plaster is done without mesh reinforcement. In consistency, the solution is much denser and resembles a tough dough.
Application of the second layer - primer
For mixing take 25 kg of cement, 75 kg of sand (about 5 buckets), 17- 20 liters of water.
The components are mixed in the same sequence, but liquid soap is added along with water - about 1 teaspoon per bucket of cement. Many add PVA glue, dish detergent, antifreeze to increase the frost resistance of the coating. Only commercially available plasticizers can be used. These additives are not required components, but they significantly improve the quality of the plaster and make it easier to apply.
Plasticizers improve the properties of the composition
The third layer is called a cover, and the finest fraction of sand is used to mix the solution.
Sand for plaster
The layer thickness should not exceed 3 mm. Professional builders recommend adding lime dough to the finishing layer, due to which the mixture becomes very plastic, easily rubbed, and does not shrink.
In the presence of a concrete mixer, the kneading process takes place differently: first, 2/3 of the required amount of water is poured into the concrete mixer, then cement is poured, mixed for 2-3 minutes.
Next, sand is poured, the remaining water is added and again mixed for 3-4 minutes. If lime is used, it is added at the same time as cement.
Lime dough should be prepared at least two weeks before the start of plastering work, and even better - a month. Correctly slaked lime can be stored for a very long time and used as needed.
For extinguishing, a deep metal container without traces of corrosion is required. When lime is mixed with water, a lot of heat is generated, the temperature can reach 100 degrees and above, so containers made of plastic, especially thin plastic, are completely unsuitable. So, lump lime is poured inside and poured with cold water at the rate of 1 part of water to 2 parts of lime.
Important! Quicklime is a very caustic substance, so you need to work with it with protective gloves and a respirator. Do not allow contact with skin and mucous membranes - this will cause severe irritation.
Building quicklime ground
Step 2. Mix the contents thoroughly with a shovel or wooden stick containers to speed up the hydration process. Depending on the composition of the lime, slaking can take from 8 to 30 minutes.With a decrease in vaporization, the mass is mixed again, and so several times.
Step 3 .
After the termination of the reaction, the lime is stirred again, the container is covered with a lid and left for 2 weeks. The mass becomes plastic, all lumps dissolve without a trace and can be added to plaster solutions.
For large volumes of work, a hole is dug for extinguishing a depth of at least 1 m, lime is poured there and watered with water from hose. When the mass stops boiling, a thick layer of sand is poured on top and the pit is covered with boards or a wooden shield. After 15-20 days, the lime dough can be used as directed.
To knead the cement-clay mortar, the clay is prepared in advance. It must be well soaked, otherwise the quality of the plaster is very low. Since it is much more difficult to sift dry clay than sand, before soaking, they simply pick out all the garbage, grass blades, large pebbles from it with their hands, and before mixing the solution, filter the clay dough through a sieve.
Step 1. Pour 1 part of clay into a wide trough or box for mortar and fill it with 3 parts of cold water.
Stir with a shovel so that the clay is well wet, and leave for at least 5 hours, or better - for a day.
Step 2 . When the clay is completely wet, mix it again, knead the remaining lumps with your hands.
Step 3 . When mixing cement mortar, clay dough is added after mixing sand and cement, if the work is done manually, and together with cement, if the mortar is prepared in a concrete mixer.
Example of facade plastering
Everything is very simple here. For mixing, you need a clean container, water and a construction mixer. Read the instructions on the package, take the indicated amount of water and pour it into the container. Now you need to pour the dry mixture from the bag into the water and use a mixer to bring the mass to homogeneity. After that, you need to leave the solution for 5-7 minutes (the exact time is written on the package).
Then mix again and plaster the surface.
Recall that mixing is recommended to use a special construction mixer
Series of works before applying the plaster on the facade
Features of plastering of building facades
Mixtures for leveling walls and ceilings
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