Leveling the floor using special mixtures

During the construction of buildings in Russia, the slabs that serve as the basis for the floors in serial houses are made smooth only on one side – the one that will become the ceiling of the lower apartment. But the side that is to become the floor has an uneven surface with bumps and depressions, in addition, very often the ends of the metal reinforcement rods can be seen from it (as a result, the floor level drops in the apartment can reach 12 cm. Naturally, on such a surface, no what conditions it is impossible to lay the front covering with high quality.In this article we will show you an excellent way to level such a floor using special leveling devices, in other words, creating a screed.

Screed for a perfect floor

In Russia, the screed was traditionally made from dry concrete mixes. But since a mixture of concrete with sand in any proportion is not a very durable material, this rather outdated method of leveling floors was replaced by the European fashion for self-leveling floors, in the manufacture of which special self-leveling mixtures are used.

For additional noise and heat insulation, a layer of expanded polystyrene is often placed under these mixtures. Such a floor dries much faster than a conventional screed (in a few days).

Any finishing coat can be laid on self-leveling floors: tiles, laminated carpet, etc. In addition, the self-leveling floor layer has a very small thickness, which is especially convenient in apartments with low ceilings.

All floor levelers can be conditionally divided into two large groups: the first is intended for initial, rough leveling, creating the main thickness of the screed. The second is for the final, finishing layer, creating a smooth surface.
Leveling agents for initial leveling have a coarse fraction of components, due to which it is possible to apply the mixture in a sufficiently thick layer (but it is almost impossible to create a perfectly smooth surface) The leveling agent for finishing leveling, on the contrary, has a fine fraction, it can only be applied in a thin layer, while the surface is perfectly smooth.

Screed laying

In this section, we will highlight only general recommendations for installing a floor screed. Read the manufacturer’s instructions for specific values, mixing ratios, setting times for setting and drying. So, first we list the tool that will be needed for these works:

• Deep capacity (bucket)
• Brush
• Steel wide spatula
• Drill
• Mixer attachment
• Roulette
• Hydro level

Before starting work, make sure that all window and door openings are tightly closed. During the execution of work, the temperature of the base of the floor and the air in the room should be within the range of + 10oС – + 25oС. During the execution of work and within 1 day after their completion, avoid drafts and air draft on the floor surface (while the relative humidity of the base should be < 95%).

Flaking and weak concrete, cement glue, oil, carpet glue and water-soluble leveling compounds must be removed before screed.

To prepare the base, it is necessary. This treatment improves the adhesion of the leveling compound to the base, prevents the formation of air bubbles and too fast absorption of water from the leveling compound into the base.

Primers also improve the flow of the leveling compound. Dry and highly absorbent substrates (monolithic concrete floors) should preferably be treated twice.

When laying the screed, remember that any floor screed can be sealed with water. Therefore, in order to prevent liquid from flowing through small cracks invisible to the eye, waterproofing should be applied (do not forget to maintain the time required for each layer of the applied material to dry, this time is indicated in the instructions for use of the building materials you purchased).

When the base is completely ready, a level is displayed around the perimeter of the room. This is done like this: at a certain height from the floor, an arbitrary mark (risk) is placed and measurements begin from it.

It is better to carry out this procedure in pairs: one puts the flask at risk, and the other moves further along the wall with the second flask and leans it against the wall.

Having achieved that the water in the flasks coincides with the set risk on the wall, they put the second risk where the second flask is. And so along the entire perimeter of the room. Please note: 4 marks in the corners may not be enough, it is better to put intermediate marks in the described way.

Then a long strip or plastering line is taken and a line is drawn connecting all the risks. It turns out an absolutely flat line around the perimeter of the entire room.

The next step, using a tape measure, measure the distance from the resulting line to the base and find the highest mark. The most painstaking stage is the installation of beacons. The quality of this work depends on how flat the floors will be. For this, you can use plaster beacons (a beacon is a special profile with a certain height). The lighthouses are mounted on the base, parallel to each other, on the same level. The distance between them should be no more than the width of the tool used for leveling..

Check according to the instructions of the manufacturer of the leveling agent the maximum thickness of the mortar application (if the thickness of your future screed is too large, then the leveling agent will need to be applied in several layers).
Only after installing the beacons can you start preparing and mixing the roving: for this, take a container with clean water, gradually add the dry mixture to it, stirring constantly. Mixing is best done with a powerful drill at low speeds (with a mixer attachment) until a homogeneous mass is obtained without lumps and clots..
The finished mixture is suitable for use within 30 – 50 minutes from the moment of mixing with water. The temperature of the leveling compound must not be lower than + 10oС.

When mixing the leveling agent, strictly observe the proportions set by the manufacturer of the dry mix and do not overdose with water, because the introduction of an excessive amount of water can cause foaming of the solution, reduce its mechanical strength and lead to delamination of the material.

The finished mixture is spread on the base, gradually filling the space to the lighthouses. Spread the mortar evenly over the entire leveling surface. To remove air bubbles, the surface of the freshly laid mortar can be rolled with a needle roller.

If the pouring area exceeds 20 m2, then it is necessary to perform expansion joints, dividing the area into technological sections. The thickness of the expansion joint can vary from 5 to 13 mm, depending on the material used. When the leveling agent reaches the level of the beacons, simply place the trowel on two adjacent beacons and finally level the solution.

Laying the finishing solution

If you want a perfectly smooth floor after a rough screed, you should use a finishing leveler for the floor. To use the finishing leveling agent, the same temperature and humidity conditions must be maintained as when working with the subfloor described above: the base must be free from dust, dirt, grease, fragile parts of the base must be removed.

Floor screeds are diluted to a liquid state, which makes it more likely to leak to lower floors than when using screeds for the initial leveling. Therefore, if you are leveling the original concrete floor, waterproof.

Due to the fact that the finished solution turns out to be liquid, it spreads perfectly over the surface under the force of gravity, accumulating in places of the smallest heights and depressions. Considering that in most cases such leveling agents are not applied thicker than a few millimeters, measure the level of the base around the perimeter with particular care, otherwise the solution will simply drain into one corner (there are self-leveling leveling agents with an application thickness of up to 30 mm). When using this leveling agent, beacons can not be used, the solution will spread by itself, creating a horizontal surface.

That, perhaps, is all, at first glance, simple recommendations for screed construction and installation of finishing self-leveling floors. But with apparent simplicity, this process requires special professionalism and accuracy of specialists and the quality of the materials used..

For this reason, if you want the floors in your house to be perfectly even, durable and beautiful, you should not chase the “long ruble” by asking for help from dubious companies and purchasing unknown materials. After all, the floors in the house are arranged not for one and not for two years: and the maximum service life and quality are guaranteed only by specialists who know their business.