Waterproofing plaster: DIY application technology

The main purpose of plaster mixes is to prepare the base for finishing, that is, in rough leveling and surface hardening. But there are also such plasters that, in addition to their basic functions, perform other tasks: they increase heat and sound insulation, protect against harmful radiation, give the base fireproof properties, and so on. They are called special-purpose compounds, and are used taking into account the functional characteristics of these solutions.

Waterproofing plaster, which is used for finishing surfaces exposed to increased moisture influence, is also a special one. First of all, these are foundations, basements, basements, outer walls of houses located in damp areas.

What is the difference between this plaster and the usual one, and how should it be applied correctly?

Characteristics and properties of waterproofing plaster

Waterproofing mixtures form a dense hard coating that prevents moisture penetration into the thickness of walls or foundations. They are applied manually and by machine, used both outside and inside the premises. Depending on the composition of the components, waterproofing plasters are divided into 2 types:

• cement-sand;
• asphalt.

The first type is more common and is widely used in private construction. Cement-sand plasters can be made independently, and the process of their application is almost the same as usual plastering.

For the preparation of the solution, cement grade M400 and higher is used, and fine quartz is used as a filler sand, stone flour, finely ground coal, bituminous additives. To increase the water resistance, liquid glass, ceresite, sodium aluminate and other water repellents are added to the solution.

The ratio of binder and filler is usually 1: 2, less often 1: 3. For maximum effectiveness, the thickness of the coating should be 25 mm, provided that the plaster is applied from the water pressure side. Application is carried out in several layers, the minimum thickness is 3 mm.

Such waterproofing has many advantages:

• high reliability even with prolonged flooding of the foundation and walls of the house;
• resistance to repeated freezing;
• environmental safety - you can finish plastering internal surfaces of drinking water tanks;
• plaster serves as an excellent base for painting and lining;
• has good adhesion;
• low cost of mortar;
• resistance to mechanical damage.

In order for the coating to be of high quality and durable, it can be applied only on a carefully prepared substrate.In addition, the surface must be strong and not prone to shrinkage, otherwise the plaster will crack. For work, it is preferable to choose factory mixes with clearly verified proportions of components. They are produced in dry form, and to prepare a solution, it is enough to mix the powder with water in the desired ratio.

Asphalt plaster is mainly used in industrial facilities. Its cost is quite high, and special equipment is required for application, therefore, in private construction, the use of such waterproofing is not always justified. The plaster contains petroleum bitumen, asbestos dust, sand and mineral fillers in the form of powder.

There are two ways to apply asphalt plaster - cold and hot. The cold mortar is applied manually or by machine and is much easier to work with.

The second method involves heating the solution to 180 degrees and applying it using special equipment. In this case, the waterproofing is as reliable and durable as possible.

Popular brands of cement-sand plaster for waterproofing

Consumption of conventional waterproofing plaster averages 1.

5 kg per m2 in a single layer application. The consumption of penetrating compounds is less - about 0.4-0.6 kg / m2. Of course, this indicator directly depends on the quality of the surface, the method of application and the thickness of the layers, therefore, before buying the material, you should carefully calculate everything and add 10-15% of the estimated amount of the mixture in reserve.

Prices for waterproofing plasters

Waterproofing plasters

Conditions for applying plaster

Waterproofing plasters must not be applied to crumbling, loose substrates, coatings containing gypsum, as well as surfaces with efflorescence, traces of bitumen, paint, oil stains. All this reduces adhesion, which means that the plaster will not last long. It is also unacceptable to plaster the bases with cracks, the width of which exceeds 0.5 mm.

To properly prepare the surface, you must completely remove layers of paint, old plaster or putty. If the paint is difficult to remove, it is advisable to soften it by heating it with a hair dryer or special chemical washes. After that, it can be easily removed with a spatula. The plaster and putty are cleaned with a metal brush, you can also use a grinder with a nozzle. An excellent result is obtained by sandblasting.

Seams of brick and masonry must be cleaned with a metal brush and dedusted. If the masonry is old and the seams are crumbling, they are cleaned out to a solid base and then filled with fresh cement mortar. Cracks must be sewn to a depth of 1-2 cm before sealing and cleaned of dust.

When finishing surfaces with a heterogeneous structure (concrete and brick, brick and stone), the base is preliminarily plastered with a conventional cement-sand mixture.

Like ordinary plaster, the waterproofing layer needs to be reinforced if its thickness exceeds 10 mm.

When plastering rough masonry or a surface with numerous defects, when the mortar is applied in a thick layer, a galvanized metal mesh with cells from 10x10 mm to 20x20 mm is used for reinforcement.

It is fixed to the base using plastic dowels and self-tapping screws with an attachment pitch of 40-50 cm.

On a flat surface, use a fiberglass mesh, provided that there is no layer thickness exceed 30 mm.

At least 3 months must pass between the erection of the masonry and its waterproofing. This also applies to concrete foundations.

If preliminary leveling is performed with ordinary cement mortar, waterproofing plaster can be applied no earlier than after 28 days. Plastering should be done in dry, windless weather, at a temperature not lower than +5 and not higher than +30 degrees. The optimum air humidity is 60%. Moreover, such conditions must be observed not only during the application of the plaster, but also within several days after the completion of the work.

Prices for plaster nets

Plaster nets

Plaster application technology

Plastering is carried out manually or mechanically.

The first option is much more practical, since it does not require equipment and the solution consumption is less. True, it takes more time to work, and the reliability of adhesion to the base is slightly lower. The mechanical method allows you to do everything much faster and without much physical effort, moreover, with such an application, the solution adheres very tightly to the surface, and the coating acquires high strength. The disadvantages include the high consumption of the working mixture and the need for a special installation.

Manual application

For work you need :

• container for mixing;
• building mixer;
• metal spatula;
• paint brush with semi-hard bristles;
• pure water.

Step 1. The prepared surface is slightly moistened with water using a wide brushes. The base must be wet, but not wet, especially since there are no puddles on horizontal surfaces.

Step 2. B the container is poured with clean water at room temperature, the dry mixture is poured in and stirred with a mixer at a speed of 400-800 rpm for 3 minutes.

The proportions of water and dry mix are indicated on the package. If this is a two-component composition, first the emulsion is poured into the container, water is added (if indicated in the instructions), stir and only then the dry components are added. For the first layer, the solution is made more liquid: on average, 1 part of water is taken for 2.5 parts of the dry mixture. After mixing, leave the solution for 5 minutes to ripen, then mix again with a mixer.

Price for construction mixer

Construction mixer

Step 3. The first layer is applied with a brush, performing movements in one direction. The solution is collected a little, carefully rubbed over the surface, paying special attention to the joints. Make sure that the layer remains uniform over the entire area, avoid sagging and sagging. It is not recommended to return to the already treated areas in order to fix something, this violates the integrity of the layer and reduces the adhesion of the material to the base.

Step 4. After finishing applying the plaster, wait until it starts to harden ... After that, the next portion of the solution is prepared, but less water is added this time: about 1 part of water to 3 parts of the dry mixture.

Step 5. For the second coat it is better to use a trowel. Collect the solution in small portions and evenly distribute it over the base with a thin layer from bottom to top, holding the spatula at an angle to the surface. Movements with a spatula must be performed in a direction perpendicular to the direction of the hand. That is, if you applied the first layer with vertical movements, then the second should be applied horizontally.

If a third layer is required, this rule must also be followed.

Step 6. The plastered surface must be protected from drying out, mechanical stress , direct sunlight. If the weather is too warm, the plaster should be periodically moistened with water using a spray bottle. After 7 days, when the coating gets stronger enough, the plaster is trowelled.

To do this, make a liquid solution, throw it in a thin layer on the surface and smooth it in a circular motion using a polyurethane or metal float.

Immediately after plastering, the coating must not be trowelled, as this violates its density and adhesion to the base. You can continue finishing work in 3-7 days, depending on the composition of the plaster. For example, a Barralastic coating can be tiled already 20 hours after the last layer is applied, for Ceresit CR 65 it takes 3 days, for Penetron - from 7 to 14 days.

Mechanical application

Mechanical application, or gunning, is carried out using a special installation with a compressor and a nozzle.

Smooth concrete base before gunning is treated with a sandblaster or small incisions are made manually over the entire area.

On bases with a rough uneven surface, a reinforcing mesh made of galvanized metal is preliminarily fixed.

Step 1. The work surface is slightly moistened.

Water is poured into the installation container and the dry mixture is poured in the proportions indicated by the manufacturer.

Set the pressure in the range of 0.25 ... 0.

3, MPa, check the supply of the solution in a separate section of the wall. If the mixture begins to float, slide down, it means that there is an excess of water in the solution, and dry components should be added, if dry spots form on the plaster layer, add water.

Step 2. For uniform application of the solution, the nozzle is held perpendicular to the wall at a distance of 80-100 cm from the surface, slowly moving it in a circular motion. The thickness of one layer should be between 7-10 mm.

After completing the work, the plaster is covered with plastic wrap to protect it from drying out.

Tip. If a forced break is required in the work, the edge of the plaster in the already treated area is cut off at an angle of 45 degrees and scratched with a metal brush over the fresh mortar. After the resumption of the working process, the cut site must be abundantly moistened with water.

Step 3.

The next layer is applied one day after the first, the same interval is maintained before applying the third layer. The total thickness of the coating must not exceed 50 mm.

Step 4. After the plaster has hardened, a liquid solution is prepared, manually applied it on the coating and grout with a metal or polyurethane float. Next, cover the surface with polyethylene or periodically moisten it with water to avoid cracking.

For 7 days, the plaster must be protected from freezing, direct sunlight, mechanical stress. If everything is done correctly, after drying, the coating has an even color, a smooth hard surface, when tapped with a wooden hammer, it emits sonorous sounds.

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Video - Waterproofing plaster