The Technological Process Of Creating A Semi-dry Screed Indoors

2023 Author: Philip Bishop | [email protected]. Last modified: 2023-08-25 07:54

• Concept
• Application area
• Pros and cons
• Dry screed options
• Foundation preparation
• Insulating layers
• Fixing beacons
• Proportions of cement and sand
• Installation work
• Grout
• Thorough care

In the modern construction industry, there is a sufficient number of floor screeds. Among them, it is worth highlighting the semi-dry screed, which is also used to reduce the time required to complete all types of work at the facility. A semi-dry screed can be performed not only with the use of a special tool, but also independently. There are both advantages and disadvantages here. The most important thing is that the result is a really flat surface, already used under the flooring.

Concept

Semi-dry floor screed is not particularly innovative. It also uses prepared sand and cement. True, a very minimal amount of water use. The solution should not give any leak. It will be sufficient to make a lump out of it. Here it cannot even be said that the device of a semi-dry screed is performed by "filling", but rather by ordinary filling. In addition to everything, it is important to apply some subtleties that allow you to get the most durable surface. We are talking about the reinforcement of a semi-dry screed, when it is customary to use fiber as a material. This product is composed of polypropylene fibers.

Depending on what kind of result it is necessary to obtain for the floor screed, certain technologies are also distinguished. An increase in the screed layer occurs when laying communications, whatever they may be. A lot of attention is paid to floors with large elevation differences.

Application area

As mentioned earlier, the semi-dry screed technology finds its application in the case of reduced terms for repair work. There is a great desire to quickly move into a purchased apartment, when all types of work are especially carried out on their own. This should also include very thin floor slabs. In this case, there is a high probability that the prepared "wet" solution will get to the lower floors.

The basis for a semi-dry screed can be:

• Slabs made of wood, which are often found in old buildings.
• Concrete floor slabs used in modern construction.
• Soil bases (gravel, sand, compacted material). This can be encountered in private households, when arranging basements, when organizing a semi-dry screed on the first floors of buildings.

Pros and cons

From the type of material used for work, as well as the installation technology itself, each screed option has its positive and negative sides. A semi-dry screed is no exception. The device of semi-dry floors highlights the following advantages:

1. Acceptable cost of purchasing the necessary material, as well as wages for workers.

2. The probability of the floor cracking, the appearance of any defects is reduced to zero. The result obtained retains its qualities and properties for a long time.

   

3. It is not necessary to carry out additional measures for the implementation of floor leveling. After completing all types of work, you can start laying the flooring.
4. The characteristics of heat and sound insulation are significantly increased due to the existing porosity of the finished "rough" floor.
5. There will be no leaks during installation work, since the use of water is minimized.

But this is only the main part of all those points that recommend carrying out the device of a semi-dry floor screed even on your own. It is worth noting that there are no significant negative qualities noted if the work is done by hand. This suggests that this method is very practical and of high quality in terms of the final result.

Large areas are very costly to level when using this technology. In addition to the purchase of the material and equipment itself, you will have to spend money on delivery to the place of work, supply using specialized flexible pipes.

The disadvantages include the need to use additional equipment for mixing. Preparing a semi-dry mixture will be problematic and difficult on your own. If you are not confident in your own capabilities, then it is best to turn to specialists. Excess water can ruin even very expensive and high-quality brands of cement. It is important to perform a thorough ramming here in order to avoid cracking during operation. It is the latter that causes the squeak under the floor covering.

Dry screed options

In order to implement the device of a semi-dry floor screed, completely different technology can be used. For this reason, there are some options for carrying out floor leveling work:

• No underlay is applied, but the screed is carried out directly onto the prepared concrete base.
• Using a polyethylene backing. No adhesion to walls and base. Thus, the so-called "floating" version of the screed is obtained.
• On the surface of the laid screed, work is carried out on the device of the sound insulation membrane.

• Thermal insulation materials can also be used as a substrate.

  

Each of these options is capable of performing certain functions, depending on what kind of flooring is used and what result should be obtained upon completion of the work. Very often, a semi-dry cement-sand screed with fiberglass is performed. It acts as a reinforcing base, which increases not only the quality, but also the reliability of the entire structure.

Foundation preparation

The service life of the floor will depend on how competently all the preparatory measures are performed. When cleaning the base, all possible layers of the old screed must be removed, up to the floor slabs. All debris is taken out, and small elements and dust are removed when using a construction vacuum cleaner. After that, it is important to prime the surface. Even minor damage to the base is smoothed out with fine sandpaper. A cement mortar will be needed to smooth out large areas of imperfection.

When areas where peeling of the base have occurred are noticed, it is cleaned with sandpaper. In the future, it remains only to seal the damaged areas with putty.

When determining the amount of solution for work, attention is drawn to detailed measurements when using a special tool,

which can be a normal level. Better measurements are carried out using a laser level. True, not everyone will have it in stock, which will manifest itself when performing work on their own.

The horizontal is set along the walls. Existing differences in height should be detected in time so that later you do not waste time buying an additional portion of materials.

The work of a laser level is that it is initially installed in the central part of the room, and a self-tapping screw is screwed into the floor (length at least 100 mm). A rule is put on it and a mark is made in the place where the laser beam intersects with the rule.

Actions are carried out in the same way near the opposite wall. When the beam and the mark do not match, it is enough to screw in or unscrew the self-tapping screw to the required limit. The same is done for all the necessary rooms in the building. To make the quality of work high, about 13-17 self-tapping screws are screwed along the walls, and one of them is fixed in the central part of the room.

Insulating layers

For waterproofing the floor, polyethylene film is most often used. The main thing is that its indicators are within 100 microns. If only pieces of film are laid out, then they should overlap by 15-20 cm on each other, as well as on the walls. On top of it, a layer of thermal insulation is laid, made of sheet insulation. It is important to choose a quality material that can last a long time and convey its qualities to all surfaces.

The best option is to use extruded polystyrene foam plates for thermal insulation. When a semi-dry screed is performed with a sufficient height, expanded clay is also suitable. Moreover, its fraction should be at most 0.6 cm.

All walls in the room, existing projections, columns, and possible elements of architecture are subject to insulation. For this, a damper tape is purchased, which has a purl adhesive base. The semi-dry screed method involves lifting tape and other layers of insulation above the level of the future casting. Subsequently, all this is removed with a construction knife.

Fixing beacons

An important and crucial stage is the location of lighthouses around the perimeter of the room. The alignment of the semi-dry screed will depend on it. They are necessary not only to emphasize the rule, but also to evenly distribute the finished solution throughout the room.

The requirements are very high here. For this reason, it is best to choose a T-shaped profile that has a corresponding name - "beacon" profiles.

By choosing one of the walls as a reference, the profiles are positioned parallel to it. It is best to fix the initial beacon at a distance of about 20-25 cm from the wall. Their further location depends on the convenience of performing all subsequent work. The most important thing is that the rule is longer than the stride of the beacons.

There is an option for cement beacons, which are made by screwing self-tapping screws into the base and filling them with cement mortar. But this is a rare method that is not highly effective.

Proportions of cement and sand

When preparing a solution for a semi-dry screed, the existing proportions should be carefully observed. From the materials you need:

• The recommended grade of cement is Portland cement M500 d0.

• Coarse sand that needs to be sieved or it can be washed. There shouldn't be any leftovers here. Its size should not exceed 25-30 mm and correspond to the first class.

  

• Purified well water. Otherwise, you may encounter water contaminated with various impurities and domestic wastewater. Approximately 15 liters for every 200 kg of mixture.
• For each square meter of mortar, about 40 grams of fiber is purchased. Has a semi-dry screed with fiberglass weight is insignificant. In this case, there is no need to reinforce a semi-dry floor screed.
• Plasticizer. A liter of such material will be sufficient for 100 kg of cement.

Cement and sand are mixed in a ratio of 1 to 4 or 1 to 5 (it all depends on the strength). Subsequently, fiber and water are proportionally poured into the finished solution. With regard to moisture, the optimal preparation of the mixture is a squeeze in a fist, in which a small amount of moisture appears, and the lump itself remains intact.

In order not to bother and not waste extra time, everything can be purchased in the store. For screeds, a semi-dry mortar is presented in the range.

Installation work

The prepared solution, when distributed over the surface, should not stick to the instruments, but smoothly spread over the entire surface. In this case, no crackling of the semi-dry screed should appear. The installation of a semi-dry screed includes not only the distribution of the mortar, but also a slight pressure at the junction of the insulating layers with the walls. It will not be superfluous to tamp it around the entire perimeter so that no air cushions appear.

Special equipment for preparing the mixture can also be used. But in this case, the entire surface should be simultaneously filled with solutions, and only then should the leveling be started. The consumption of a semi-dry floor screed will depend on the thickness of the surface under the floor, as well as the area of the room itself. The thickness must be at least 30 mm. All installed beacons can be hidden under a semi-dry screed.

Grout

As soon as the screed is thoroughly rammed around the entire perimeter, you can start leveling it. The edge of the rule rests against the exposed beacons and gradually shifts to the opposite side. This additionally indicates those places where little or, on the contrary, a lot of solution is poured. Using a trowel or trowel, the areas are adjusted to the optimum position.

The final stage is the grouting of a semi-dry screed. The best option is to use specialized equipment, which is a grinding machine on discs. The trowel is suitable for DIY work. The technology of laying a semi-dry floor screed provides for the implementation of circular movements for grouting.

Thorough care

The process of a semi-dry floor screed does not take much time. But it is necessary to create conditions that the resulting solution could solidify on the surface. Most often, a plastic wrap is used to cover it. It creates an optimal temperature regime around the entire perimeter. The preliminary result will be noticeable after 10-12 hours. If minor voids appear, they can be filled with a semi-liquid cement solution. An alternative is constant watering of the surface with water.

It is possible to start laying the floor covering only 94 hours after the polyethylene has been removed from the surface of the "rough" floor. But even during this time it is necessary to monitor the condition of the canvas.

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