A common flooring option that provides an excellent compromise between conventional wet screeds and dry screeds is semi-dry screed. It’s a flexible option that works well in both home and business settings. With this technique, a mixture with precisely the right amount of water is used to hydrate the cement without becoming overly moist. The end product is a firm, workable compound that is simple to shape and level.
The short drying time of semi-dry screed is one of its key benefits. A semi-dry screed is often ready for further work within hours, in contrast to traditional wet screeds that can take days or even weeks to fully cure. This makes it a great choice for projects that need to be completed quickly because it allows for quicker turnaround times without sacrificing quality.
Furthermore, the semi-dry screed technique provides superior acoustic and thermal insulation. Because the screed can be put directly over the heating pipes, ensuring effective heat distribution, it’s a great option for underfloor heating systems. It also lessens the transfer of noise from floor to ceiling, which makes it a sensible option for multi-story buildings.
We’ll go over the main features of semi-dry screed in this post, along with application methods, preparation steps, and advice on how to get the best results. Knowing these fundamentals will assist you in making wise decisions for your flooring projects, regardless of whether you’re a professional contractor or a do-it-yourself enthusiast.
Aspect | Details |
Definition | A semi-dry screed is a type of floor screed that uses less water, resulting in a drier mixture that"s easier to work with and faster to dry. |
Advantages | Quicker drying time, less risk of cracks, smoother surface finish, good for underfloor heating. |
Application | Ideal for indoor floors, especially where underfloor heating is installed, as it provides a solid and level base. |
Mix Ratio | Usually involves a mix of cement, sand, and water, with a consistency similar to damp sand. |
Installation | The mixture is spread, compacted, and leveled, often using a laser level for accuracy. |
- Concept and comparison with standard
- Regulatory regulation
- Characteristics
- Equipment for the device by a mechanized method
- Materials and tools
- Creation technology
- Care after the arrangement
- Advantages and disadvantages
- Average costs
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Concept and comparison with standard
A series of operations known as semi-dry (machine) screed are intended to level the floor prior to the application of the final coating.
Its high accuracy in adding water sets it apart from traditional wet concrete pouring techniques. This is required to ensure that all of the liquid in the solution has been absorbed into the cement after drying.
Since semi-dry concrete can be used nearly immediately after hardening, ordinary concrete can take up to four weeks to dry, so this option for leveling the floor is used when it’s necessary to expedite the drying process.
The solution’s surface can be smoothed 24 hours after it is laid, and the finishing coat is applied after 3 days (for materials that don’t mind getting wet, like porcelain tiles). It is recommended to install parquet flooring after 1.5 months, while less stable flooring such as carpet or linoleum can be installed after two weeks.
When choosing this course of action Since voids frequently form in the places where the mixture meets the walls and lighthouses, it is necessary to closely monitor the density of the mixture during pouring. Because there is less water in the concrete composition, the half-dry screed is less flexible and will fit less well in these types of environments. Add a plasticizer to the solution to fix this.
Half-dry screed differs from regular screed in another way: it requires specific tools (a grouting machine and solution pump), making it challenging to complete on your own (it is advised to hire specialists).
In order to achieve maximum levelness on the floor, apply a semi-dry screed. It is advised to perform a black fill, usually the standard wet version.
Semi-dry screed lessens the load on the floors and can be applied on surfaces with a slight slope. Floors made from a solution with a minimum amount of moisture are most frequently used in high-rise buildings so that when the mixture dries, the ceiling covering of the rooms below is not damaged.
See this article for additional details on the variations with wet screed.
With a faster drying time and a smoother finish, semi-dry screed is a flexible and effective flooring option that blends the advantages of conventional wet screed with contemporary methods. By using less water, this technique lowers the possibility of shrinkage or cracks and makes the material easier to work with. When building a new space or remodeling an old one, semi-dry screed offers a level, long-lasting surface that is prepared for a variety of floor coverings.
Regulatory regulation
Documents exist that outline the specifications needed to produce superior semi-dry screed. Take "Concrete Mixtures" (GOST 7473-94) as an example. Technical specifications" list the qualities that the solution ought to possess both during pouring and following drying.
The requirements outlined in SNiP 3.04.01-87 "Insulating and finishing coatings," SNiP 2.03.13-88 "Floors," and MDS 31-6.2000 "Recommendations for flooring" form the basis of the technological map for floor arrangement.
Requirements for the caliber of materials used in the floor pouring process based on:
- GOST 8736-93 “Sand for floor screed”;
- GOST 25328-82 “Cement for mortars”;
- GOST 7473-94 “Concrete mixtures”;
- GOST 28013-89 “Building mortars”.
The qualities that the material used for semi-dry screeds should have are described in these documents.
Characteristics
Semi-dry screed is characterized by the following features:
- mixture strength when using M150-250 grade concrete is from 150 to 250 kg/cm2;
- shrinkage during drying is 0.2 mm/m;
- the minimum layer thickness is 30-40 mm, and the maximum is not recommended to be more than 5-6 cm;
- drying of concrete for pedestrian loads is 12-24 hours, and full 3-4 weeks.
The maximum allowable concrete layer when using fiber to reinforce the solution is 80 mm, and the minimum is 1 cm. However, as the thickness increases or decreases, there is a greater chance that the floors will deform due to excessive load.
Equipment for the device by a mechanized method
You will need specialized equipment to create a semi-dry screed because it is nearly hard to mix and apply such a mixture by hand due to the solution’s lack of water. To put in a floor like that, use:
- A pneumatic pump is a barrel in which the solution is mixed, which can then be poured onto the floor using a special pipe and compressor.
- Dampener, which is needed for a smoother flow of the mixture.
- A trowel is a device that removes all irregularities on the surface of the screed so that the final coating can be applied.
Without such equipment, it will be challenging to pour a semi-dry mixture because the thickness of the concrete makes it difficult to mix the solution without using a lot of water, as is typically the case with a wet screed.
Materials and tools
For creating a semi-dry screed, the following equipment and supplies are required:
- pneumatic supercharger;
- quencher;
- hose-sleeve with a handle, which is needed to supply the solution (diameter 65-80 mm);
- laser level for leveling;
- a 220 V grinding machine, the diameter of the circle of which is 600 mm;
- trowel. This is a device that helps to level the floor surface in places where the grouting machine cannot reach;
- air hose from the compressor to the pneumatic pump, which is used to increase the pressure inside the machine, due to which the mixture is supplied;
- concrete mortars – attachments for shoes to walk on the solution;
- cement brand M500 (less commonly M400, the shelf life of which is less than 2 months);
- sifted dry sand, which does not contain clay additives (no more than 3%) with a fineness modulus of up to 2.5 units.;
- fiber;
- waterproofing;
- pipes up to 3 m long, which will be used as beacons;
- damper tape;
- reinforcing mesh, which is most often used instead of fiber;
- screwdriver;
- tape measure;
- hot glue gun for damper tape;
- construction knife.
Creation technology
The technology used to create a semi-dry screed varies depending on the type of coating that is chosen. While installation techniques generally remain the same, there may be some differences.
For instance, semi-dry screed comes in three varieties:
- bound, which is laid directly on the concrete slab (after preliminary work);
- floating, which does not have direct contact with concrete, since it is laid on a layer of heat or sound insulation (for example, foam plastic, expanded polystyrene), and a damper tape (foamed polyethylene, which is cut into strips) is glued at the junction between the wall and the screed;
- the screed on the separating layer is laid on a waterproofing film up to 1 mm thick, since when this indicator increases, the concrete mixture can be considered floating. On the walls, the solution is also separated by a damper tape.
To create a floating screed that is semi-dry, you must:
- Carry out preliminary work. To do this, you need to remove all debris from the floor surface and seal cracks or chips with cement mortar (can be replaced with tile adhesive), and then carry out preliminary leveling.
- Make waterproofing of the floor using a film or bitumen mastic.
- Glue the damper tape with hot glue or liquid nails. This will help to protect the screed and walls from the formation of cold bridges, changes in the water balance in the solution (will draw moisture from the walls), and this insulation layer will also dampen sound waves.
- A layer of soundproofing material is usually laid along with waterproofing, which will additionally serve as insulation. Foam plastic, foamed polystyrene or mineral wool are used as such a coating. A layer of soundproofing is needed because when laid on bare concrete, the screed will amplify all sounds.
- Install beacons using a level or marks on the walls, which must be made with a marker. In this case, you need to find the highest point of the floor to mark the thickness of the screed.
- Lay the reinforcing mesh on top of the insulation with an indentation from the walls of 20-30 mm.
- Mixing a concrete solution of cement, sand, water and fiberglass for 50 kg of cement will require approximately 150 kg of sand and 30-35 liters of water. This volume is enough for 5 m 2 floor with a thickness thickness of 40 mm.
- Make concrete laying. You need to raise a grid when filling so that it is inside the solution.
- To align the screed in the process of laying using the rule or the cell, as well as to compact the mixture (trampling).
Full information about the device here.
Care after the arrangement
Following laying, you require:
- Remove the beacons and close the cracks with a solution;
- Flip the surface of the floor with a grout machine after preliminary drying.
It is then advised to apply a film to the floor and use a spray gun to moisten the concrete for the first two to three days (0.5 l/m 2). This is important to ensure that the cement crystallizes during the hydration process, as the screed will become more brittle if the water dries off too soon.
It is advised to create an expansion joint on the second day in rooms larger than 25 m^2. The joint should be 3 mm wide and 1/3 the thickness of the concrete layer. Such a cut must be made in the center of the screed.
Advantages and disadvantages
Positive attributes of half-dry screed include:
- high strength subject to all norms;
- After the grout, a smooth surface is obtained, since there are no voids after the water dries;
- durability for more than 30 years;
- fast drying, as well as acceleration of the start of grouting work and laying of the final coating;
- protection against water flow during flooding of the floor;
- quick work on styling;
- small shrinkage;
- can be combined with underfloor heating and communications.
Among the drawbacks, the following must be mentioned:
- the need for special equipment and the presence of experienced specialists;
- you need to carefully monitor the amount of moisture in the solution;
- the need for special sand, since ordinary river sand is not suitable;
- it is necessary to continuously lay the solution and level it, since it dries quickly;
- reduction in sound insulation if there is no special layer under the screed. If it is, then the soundproofing properties of the screed increase, due to which it itself becomes an insulator.
A thorough evaluation of the article’s advantages and disadvantages.
Average costs
The materials and soundproofing layer determine the average cost of a mechanically made screed:
- regular semi-dry will cost 500 rubles / m 2 with a thickness of 60 mm;
- with a layer of expanded clay (final thickness 8 mm) – 650 rubles / m 2;
- when using polystyrene foam, the final thickness will be 9-12 cm, and the cost is 750-850 rubles / m 2 .
Here are more specifics regarding semi-dry screed pricing.
A practical and effective way to achieve a level and smooth surface for flooring is with a semi-dry screed. This method is well-liked for both residential and commercial projects because it has many advantages, such as shorter drying times and increased durability.
A semi-dry screed reduces the chance of shrinkage and cracks due to its lower water content, giving your flooring a more stable base. Additionally, it’s more manageable, giving you more control over the installation procedure.
Consider a semi-dry screed if you’re searching for a dependable and affordable solution for your flooring needs. It guarantees a superior finish that endures over time by fusing the best aspects of contemporary and traditional screeding techniques. This approach provides a workable and long-lasting choice for your upcoming project, whether you’re a contractor or a homeowner.