Before installing any modern flooring, a level floor is required. In order for the surface to be perfectly flat, you need to fill the floor screed.
From the article you will learn how to pour a floor screed step-by-step technology work performed.
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Like any others renovation work pouring the floor screed begins with preparatory work. First, the surface should be cleaned of dust and dirt.
Fill cracks in the floor with cement-based mortar.
It is advisable to maintain the room temperature in the range from 10 to 25 degrees.
To prevent cracking of the screed due to thermal expansion, a damper tape is used. Most often it is made of foamed polyethylene.
It also acts as a sound insulator and reduces shock loads transmitted from the floor to the walls.
IN small rooms damper tape is attached around the perimeter of the room. For private houses and other premises where the screed area is very large, it is necessary to lay a damper tape in the screed itself.
In children's rooms, bedrooms and other rooms where you spend a lot of time, it is worth considering the option of floor insulation.
Polystyrene foam boards 5 cm thick are suitable as insulation. For best warmth and sound insulation, polystyrene foam boards have a special mounting lock.
The insulation should be laid tightly to the base in a checkerboard pattern and, if necessary, secured with dowels.
For steam and waterproofing, you can use ordinary polyethylene film, the sheets of which are laid overlapping each other over the walls and secured together with tape.
An important point during preparation is the installation of beacons. It is almost impossible to level the floor without them.
Beacons are rigid metal guides, and you can also use a profile for installing drywall as beacons. Wood is absolutely not suitable as beacons, since it absorbs water when it dries.
The beacons are placed parallel to each other at a distance slightly less than the length of the rule that you will use to screed the mortar.
The first beacon is placed at a distance of 20-30 cm from the wall in small piles of cement. The next one is parallel to the first one, the height is adjusted using a level or a simple level.
The remaining beacons are installed in the same way.
The solution with beacons must be allowed to harden, usually 12 hours is enough.
The second method of installing beacons from a profile without mortar on dowels with self-tapping screws. To do this, mark the lines where it is necessary to install the beacons and drive in dowels with self-tapping screws in increments of about 80 cm.
The height of the screws is adjusted using a laser level. The profile is laid on the self-tapping screws and as the pouring progresses, they can be easily moved along the screws.
To prevent the appearance of cracks and general reliability, a special reinforcing mesh is installed before pouring the floor screed.
More often, a metal mesh with a mesh size of 10 or 15 cm is used for reinforcement. It is attached to the concrete base with dowels.
Nowadays, reinforcement mesh made of composite materials(plastic). It does not react with moisture and therefore retains its properties longer. In addition, it is not electrically conductive and does not affect the propagation of the WiFi signal in the room.
Also, when reinforcing, the mesh can be replaced with fiberglass; it is added to the screed solution. Fiber fiber provides greater strength and prevents the screed from cracking when drying.
Now you can start preparing the solution for pouring the floor screed.
Sand, cement and water are used to prepare the mixture. To mix the components, it is better to use a concrete mixer or drill with a special attachment.
Use cement grade M400 or M500.
The required proportions of the screed mortar are 1 part cement, 1 part water and 4 parts sand. First mix cement with sand and then add water.
To increase the strength of the solution, add plasticizers. They prevent cracks from appearing on the screed.
Before you begin the process of pouring the floor screed, draw a diagram or photograph all the communications that will be filled with mortar. This will help you find them and not damage them during subsequent repairs.
Start pouring from the corner of the room, which is opposite to the exit.
The solution is poured between the two beacons so that its level is slightly higher than the beacons and is leveled with a zigzag movement using a slats (rules), removing the excess. Add solution to uneven areas and level again using the rule.
We repeat the process until we fill the entire floor. It is advisable to fill the floor screed in one room in one day to avoid cracks and joints.
You can walk on the floor after 1-2 days. If the beacons are removable, then remove them and seal the remaining marks. But this does not mean that the finishing floor covering can be installed, since the screed must “mature”.
In order to properly make a floor screed based on cement mortars and concrete, the screed must correspond to the purpose of the room and have the necessary parameters for this.
The screed can become a solid foundation for the floor in any room of the house. Cement strainer is not afraid of moisture and is convenient to use as a base for flooring in wet areas, as well as outside the house - on the terraces, in the garage. The installation of heated floors in rooms is also not complete without a screed.
To install screeds, use a traditional cement-sand mortar of a grade not lower than M75. To prepare the solution, prepare a mixture of one part cement and three parts sand. The strength of the finished screed increases if the solution for laying the screed has a thick consistency.
Cement-sand mortar is easier to prepare and easier to lay in a screed than concrete. But the consumption of cement for constructing a screed of the required strength is greater than for concrete. That's why, A mortar screed is more expensive than a concrete screed.
Lime should not be added to the solution. Although lime increases the plasticity of the mortar, it reduces the strength of the screed.
Concrete of classes B10, B15, B20 is used for constructing screeds. Crushed stone and gravel are used as concrete filler. The size of the filler granules must be at least three times smaller than the thickness of the screed.
To prepare concrete for semi-dry screed, it is used significantly less water, than usual. A semi-dry screed has a higher compressive strength (up to 35 mPa) than screeds made from mortar and plastic concrete. In addition, it is less susceptible to shrinkage, which reduces the risk of cracks in the screed.
Semi-dry screed is suitable for installing heated floors. It is convenient to prepare concrete for semi-dry screed on a construction site in a special concrete mixer - mixocrete, which prepares the concrete and immediately supplies it with a pneumatic pump. flexible pipe to the installation site.
Cement mortars and concrete can be prepared at the construction site. It is recommended to include additives in their composition to increase plasticity, accelerate setting and reduce water permeability of the screed.
To obtain concrete of the required compressive strength class, It is recommended to use the following grades and quantities of cement:
During storage, cement loses its activity. The cement consumption indicated in the table is indicated for cement with a shelf life of no more than two months. The consumption of cement with a shelf life under normal conditions of more than 3 months is increased by 20%; more than 6 months - by 30-40%.
It is not recommended to use cement with a shelf life of more than 12 months.
When using old cement, the mixing time of the mixture is increased by 2-4 times. It is recommended to introduce additives that accelerate concrete hardening.
To prepare medium-strength concrete, use a mixture of 1 part (by volume) cement, 2.5 parts medium-sized sand and 4 parts aggregate - gravel or crushed stone.
The indicated ratio of mixture ingredients is approximate and depends on many factors. For example, the amount of sand in the mixture should be sufficient to fill all the spaces between the aggregate granules. For large granule sizes, the amount of sand is slightly increased, and for fine aggregate, on the contrary, it is reduced. Cement consumption is also adjusted depending on its brand, shelf life and required concrete strength (see table above).
The prepared cement mortar must have good plasticity and mobility. This solution is easier to level and compacts better. To increase plasticity, special additives are used - sulfite-yeast mash (SYB) in an amount of 0.15-0.25% by weight of cement; soap naft (M1) - 0.1-0.2% by weight of cement, and others. At home, craftsmen often add a small amount of grated laundry soap to a concrete mixer.
Mobility concrete mixture also depends on the ratio between sand and crushed stone. The best mobility is achieved with some optimal ratio, at which the thickness of the cement paste layer is maximum. When the sand content in the aggregate mixture exceeds this value, the concrete mixture becomes less mobile, which is explained by the increase in the surface area of the aggregate mixture.
To give the concrete mixture plasticity, a significant amount of more water than necessary (40...70% by weight of cement). Concrete should not be made too liquid, adding a lot of water. A screed made from such concrete will take several months to dry and will have reduced strength and frost resistance. The risk of significant shrinkage and cracking of the screed increases.
Excess water that has not entered chemical reaction with cement, remains in the concrete in the form of water pores and capillaries or evaporates, leaving air pores. In both cases, the concrete will be weakened by the presence of pores and the more water, the more pores and thus the less strength and frost resistance of the concrete.
The best option, although more expensive, is to use ready-made dry mixtures for screeding. Such mixtures are commercially available at construction market. The mixture already includes the necessary additives.
Manufacturers can include microfiber in the mixture - fibers that serve as reinforcement. Microfiber screed is more resistant to shrinkage and cracking.
There are mixtures specifically designed for underfloor heating. This should be indicated on the packaging of the mixture.
There are quick-setting compounds. On a screed made from such a mixture you can lay floor tiles within 24 hours.
The packaging of the dry mixture should contain information about what screeds and installation conditions it is intended for, what compressive strength of the screed the use of the mixture will provide.
For residential premises, the compressive strength of the screed must be at least 12 mPa, for a garage - at least 20 mPa.
By design, screeds can be connected to the base on which they are laid, or laid on a separating layer, or floating.
Screeds connected to the base, are carried out if the base is also made of concrete. For example, a screed on a reinforced concrete floor slab or on a concrete floor preparation. To ensure adhesion of the screed to the base, the surface of the latter is specially prepared - dust-free and primed. Minimum thickness ties 2.5 cm.
In screeds on the separating layer between concrete base(reinforced concrete slab or concrete preparation) and a layer is laid with a screed waterproofing film thickness of at least 0.2 mm. The edges of the film panels are laid with an overlap of at least 10 cm and sealed with adhesive tape. The edges of the film are wrapped on the walls.
The film separating layer prevents water leakage from freshly laid concrete. Dewatering of concrete reduces the strength of the screed. The screed concrete must be laid on a separating layer of film in all cases where water leakage from the concrete into the base of the screed is possible.
The minimum thickness of the screed on the separating layer is 3.5 cm.
Floating screed laid on a layer of insulation or sound insulation, for example, when installing or Minimum screed thickness 4.5 cm. subject to reinforcement. Floating screed with a thickness of more than 7-8 cm. it is allowed not to reinforce.
The screed is laid at a base and air temperature above +5 degrees C. The technology for laying screed does not change depending on whether cement-sand mortar or concrete, including semi-dry consistency, is used for laying.
The work is performed in the following sequence.
Prepare the base on which the screed will be laid. For a screed connected to the base, the surface of the base is cleaned of debris, dusted with a vacuum cleaner and primed.
To install a screed on a separating layer and a floating one, a layer of sound and heat insulation is laid, and a separating layer of waterproofing film is laid on top.
On walls and others vertical structures glue strips of polystyrene foam or edge tape made of polyurethane foam with a thickness of 1-2 cm. to create an expansion joint.
On quick-setting flatbreads cement mortar lay guide rails - beacons. Beacons are laid over the entire surface of the base in parallel rows with a pitch of approximately 1.5 m. and at a distance of 20 cm from the walls. They are used as beacons wooden slats or various metal profiles, pipes.
Special galvanized steel profiles for installing beacons are available for sale. Profiles are convenient because they do not need to be removed from the screed layer. But such profiles have little mechanical strength, increased flexibility and require careful alignment when installing on flats and accuracy when pouring concrete.
The upper surface of the beacons is leveled in one plane. If necessary, provide the required plane slope.
The solution prepared in a concrete mixer is supplied to the work site, and moving towards the door, it is evenly distributed between the beacons so that the thickness of the solution is slightly higher than the level of the beacons.
Using a grater, the solution is pre-distributed between the beacons and compacted. Finally, the solution is leveled with wooden or metal strip– as a rule, moving it along the beacons in a zigzag motion toward you. If shells remain behind the lath in the screed, they are filled with mortar and leveled again using the rule.
After the solution begins to harden and can support the weight of the worker, the beacons are removed from the screed. This is done in a timely manner, until the solution has completely set, and carefully so as not to damage the screed. If a semi-dry screed is laid, then the beacons can be removed within 3-4 hours.
The gaps in the screed left after removing the beacons are filled with mortar and smoothed with a grater, making circular movements.
Until the mortar has completely hardened, furrows are made in certain places on the screed, cutting through the mortar with a spatula to the required depth. After the solution has set, such grooves will have to be cut with a power tool with a diamond blade.
The wall expansion joint separates the screed from the walls and other vertical structural elements of the building - columns, staircase supports, etc. The seam is necessary in order to eliminate the mutual transfer of stresses between the screed and the structures of the house. Stresses can arise as a result of thermal expansion of materials or their shrinkage, as well as as a result of deformations under the influence of loads.
In addition, the seam improves the sound insulation of rooms, making it difficult to transmit sounds from the walls to the floor structures and back.
To create a seam along the walls and other elements of the building, an elastic tape with a thickness of 1 cm. to the full height of the screed.
When placing heated floor pipes in a screed An expansion joint across the entire thickness of the screed is used to separate adjacent fields of underfloor heating pipes.
In addition to the expansion joint near the walls, cuts are made in the screed, which divide the screed into smaller rectangular sections. One side of the plot should be no more than 3-6 m. IN narrow corridors compensation cuts are made across the corridor, every 2-2.5 times the width of the corridor.
In addition, compensation cuts are made at the junction of different floor coverings, as well as at the boundary of changes in screed thickness, in door openings and in other openings at the boundary of different rooms of the house.
Compensation cuts are necessary to compensate for the shrinkage of the screed material during drying. Without them, cracking of the screed may occur. The cuts are made to a depth of 1/3 - 1/2 of the thickness of the screed. The width of the cuts depends on the thickness of the screed and the presence of heated floor pipes in the screed.
If the screed is reinforced with mesh, then the expansion cuts should be located above the joints of individual mesh sheets.
If floor covering There will be tiles along the screed, then the compensation cut should coincide with the joint of the tiles.
Compensation cuts may remain empty if the flooring is parquet or laminate. The cuts are filled with waterproof silicone sealant if the floor covering is tiles.
Must be reinforced thin ties thickness 4.5-5 cm on a separating film layer. Floating screeds, the base of which is a layer of insulation (sound insulation) or compacted soil, are reinforced with a screed thickness of 7-8 cm. and less.
If the screed has a thickness greater than that specified above, then the need for reinforcement is determined depending on the operational load. For example, a floor screed in a garage for passenger car or at open terrace on compacted soil it is recommended to reinforce with a screed thickness of up to 10 cm.
Screeds made from a ready-made dry mixture containing reinforcing microfiber fibers in many cases do not require additional reinforcement.
Typically, the screed is reinforced with a mesh of steel wire with a diameter of 3-4 mm. The mesh should have cells measuring 100x100 or 150x150 mm.
The steel mesh is laid on spacer pads so that it is approximately in the middle of the screed layer. The protective layer of concrete up to the mesh must be at least 2 cm. indoors, and at least 4 cm. upon contact concrete screed with soil.
On top of the mesh, as usual, beacons are placed on cakes of mortar and leveled.
When choosing the thickness of the screed, the strength of the base on which the screed is laid, the presence or absence of screed reinforcement and the operational load are taken into account. In addition, there are restrictions on the minimum thickness different types screeds (see sections of the article above).
IN different rooms floor, the thickness of the screed, chosen for design reasons, may be different. For example, the thickness of the screed in rooms with warm floors should be such as to cover the heating tubes with a layer of at least 3 cm.
It is convenient in the house to have floors located in all rooms of the floor on the same level. Only in rooms where water can be spilled on the floor - in a bathroom, toilet, it is recommended to make the floor level lower by 1 cm. than in neighboring rooms.
To make the floors in the rooms at the same level, it is necessary to take into account that the floor covering that is laid on the screed in the rooms may have different thicknesses. For example, the thickness of the porcelain tile flooring in the kitchen differs from the thickness of the parquet flooring in the living room.
In order to determine the level of the screed surface in the room, first mark the level of finishing floor covering on the floor. To do this, choose a room where the total thickness of the screed and floor covering is greatest. The level of the finished floor in this room is taken as the level of the finished floor of the floor.
Then, the selected level of the finished floor of the floor is transferred to other rooms. The screed level in the room should be lower by the thickness of the floor covering.
In floor rooms, the thickness of the screed, selected for structural reasons, is adjusted to the specified level. If possible, adjust the level of the screed base, for example, change the thickness heat and sound insulation under the screed. Choose the most economical option.
To determine surface levels when installing screeds in a house, it is convenient to use laser device- level gauge, or hydraulic level - a transparent tube filled with water. Application of slats with bubble level will not provide the required accuracy.
Laying the screed indoors is done in one step, without interruptions. When planning work, take into account that the traditional solution must be laid within two hours after preparation. The shelf life for mortars prepared from ready-mixes is indicated on their packaging.
The solution is placed a few centimeters outside the doorway, and then the excess is cut off along the border of the expansion joint.
The surface of the screed is smoothed over with a trowel 8-10 hours after laying, until the concrete has completely set. The semi-dry concrete screed laid using a concrete pump is rubbed down after 3-4 hours. Smoothing eliminates minor roughness on the surface. There is no need to grout the screed if tiles will be laid on the screed.
The screed should remain damp for a week after installation. At this time, the screed should not lose moisture, otherwise the strength of the screed will decrease. To prevent the screed from drying out, it is covered with plastic wrap or sprayed with water daily.
After seven days, the film is removed, the room is ventilated and the screed is left to dry. After another three to four weeks, tiles can be laid on the screed. Moisture-sensitive floor coverings are laid on the screed after four to six weeks, when the moisture content of the screed is less than 3%.
On reinforced concrete floor A floating floor with a concrete screed is installed between floors. The floor is called floating because the screed does not have a rigid connection with the structure of the house.
The floating screed is separated from the walls and ceiling by a layer of elastic mineral wool. This floor design provides sound insulation between rooms of the house, and also allows the screed to move with changes in temperature and humidity.
If the floor is dry, with a humidity of no more than 3%, and the lower room is heated, then soundproofing slabs can be laid directly on the floor concrete. Otherwise, a vapor-waterproofing film is laid between the ceiling and the sound insulation slabs.
How to choose a material for sound insulation -
Sound insulation layer made of slabs mineral wool Cover the top with construction polyethylene film. The sheets of film are placed on the walls to a height of about 20 cm. The film strips are overlapped. Overlap amount 20 cm.
The film prevents the penetration of cement laitance from the freshly laid mortar into the sound insulation layer and into the edge strip.
A reinforcing mesh of steel wire with a diameter of 3 - 4 is laid on the film. mm. with cells measuring 100 x 100 mm. or 150 x 150 mm.
The floor screed can accommodate heating pipes to radiators, as well as pipes with electrical wiring. The pipes are laid on top of the reinforcing mesh and secured to it with plastic clamps.
It is recommended to wear corrugated covers on heating pipes and wires. plastic pipe. In the covers, heating pipes will be able to move freely when the temperature changes. In addition, corrugated pipes protect communications laid in the screed from mechanical damage during pouring cement mixture.
To level the cement mortar in the screed, beacons made of pipes or other profiles are placed on the reinforcing mesh. Beacon pipes are laid in increments of about 1.5 m. and level it horizontally using a level. The position of the beacons determines the thickness of the screed. Recommended screed thickness for residential premises is no more than 6 cm.
A cement mixture is placed in the space between adjacent beacons. Moving along the beacons rule or edged board distribute the mixture and level the surface.
Eight to ten hours after installation, the surface of the screed is smoothed (rubbed). Grouting can be omitted if ceramic or stone tiles will be laid on the screed.
After the cement mixture has hardened, the parts protruding from the screed are cut off edge tape and construction film.
Watch the video, which shows in detail how to mark the level and thickness of the screed in the premises.
If pipes will be laid in the screed, then it is better to use a ready-made dry mixture specially designed for this purpose to prepare the solution. The finished mixture for heated floors contains additives that increase the elasticity of the solution.
If the mixture is prepared independently, then an emulsion is added to the solution to increase elasticity. For example, home craftsmen add PVA glue at the rate of 2 l. by 1 m 3 solution.
The screed should cover the underfloor heating pipes with a layer thickness of at least 4–5 cm. Thus, the total thickness (taking into account the diameter of the tubes is 1.6 cm) will be – 6–8 cm.
Caring for the heated floor screed for the first three weeks is carried out in the same way as usual. Before laying on the screed finishing coating, the screed must be thoroughly dried. To do this, 21 days after laying the screed, turn on the heating and increase the temperature by 5 every day. °C until it reaches the limit - 24 °C.
This temperature should be maintained for 14 days, and then reduced daily by 5 °C. Consequently, heating of the screed lasts another 23–24 days, which should be taken into account when scheduling finishing work.
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Concrete floor screed is considered the most commonly performed type of floor surface repair. Thanks to physical properties, the screed made levels any surface. This article will cover the questions of what a screed is and how to make a concrete floor screed indoors.
Concrete screed is the foundation for the final coating, implemented in various ways. This structure is made from mortar and is usually the top of a layered floor on the ground or on a slab floor. By making a concrete floor screed, several important goals are achieved: a platform is created for laying the final base, a smooth distribution of the load on the concrete floor is achieved, and the solidity of the entire concrete floor as a whole is achieved.
Due to the use of water in the mixture, these screeds are called “wet”. In addition to water, it includes cement, as well as sand, which is mixed in proportions.
The concrete screed is a monolithic base and is implemented in connection with the base or with separating and insulating layers. All of the presented varieties are endowed with weak and strong points.
Installation of such a screed is carried out immediately on the base, which is prepared by applying a primer with deep penetration. This method guarantees the best grip and can withstand severe overloads. For example, a similar concrete one is being implemented.
Such a device for a concrete screed suggests that during the manufacturing process the base was laid waterproofing layer, only after that the prepared mixture was poured.
The insulation can be rolled, coated or painting materials. With this type of concrete floor screed, the technology requires that the thickness be at least three centimeters. This design is endowed with excellent moisture resistance, but the strength indicators are slightly reduced.
The use of mesh to reinforce concrete screeds is still the most common type of reinforcement. To create it, a metal mesh is used, laid on insulating material on special bedside tables, so that when pouring the solution, the mesh is in the center of the screed.
The network provides the foundation with improved strength and reliability. But it does not eliminate the possibility of cracks occurring during concrete maturation. The metal also oxidizes and over time the concrete can delaminate in the place where the network was, and this will lead to a general weakening of the product.
A new material designed to replace the reinforcing metal in floor bases is fiberglass. This material is a polymer that is added to the solution while it is being mixed and serves to reinforce the solution. Also, due to the polymer, the ductility of the entire structure is improved, which sharply reduces the likelihood of cracks.
The disadvantage of such an element is that it is necessary to strictly observe the dosage of fiber; if it is violated, the concrete screed will simply collapse and it will be very difficult to repair it.
Before the concrete screed is poured, a number of measures need to be taken, as well as purchased material.
The following tool is required:
Materials that need to be prepared:
After purchasing all the necessary parts, you can begin the repair. And the next step is to prepare the base.
The preparatory stage depends on what kind of flooring you have in the room. If a concrete floor screed is laid over the floors in a new house, then it is quite simple to clean the floor from dirt and immediately begin further installation.
The old floor needs to be prepared more carefully. It is necessary to carry out an inspection, if after it no cracks, significant chips and holes were identified, then after cleaning you can move on, but if such defects are present, then they need to be repaired, and then the repaired areas are polished.
But if the defects occupy an area of 30%, then you need to completely dismantle the old coating and fill it rough screed and perform grinding.
It is often necessary to screed wooden floors, in in this case production technology must be strictly followed to avoid destruction of the entire structure.
To avoid this, the following algorithm of actions is done:
After all the steps described above, the foundation can be considered prepared.
To achieve a level concrete floor screed, the installation of beacons is necessary, and in order to position them correctly, you need to find the zero level.
If used laser level, then the procedure looks very simple:
If you use a water level, the procedure is more complicated:
In these ways, a basic level is obtained. Then we measure the distance from it to the base, recording the obtained values on any medium.
After all measurements, we subtract the smallest value obtained from the largest.
For example:
160 – 157.5 = 2.5 cm
2.5 cm is the size of the required screed, but to achieve maximum strength, the structure must be at least 5 cm, so the screed must be made no less than this thickness.
160 – 5 = 155 cm
Thus, we got 155 cm, the value that needs to be measured from basic level already drawn on the wall and draw a line along the walls. This is how you got the zero level, which you need to focus on so that the concrete floor screed is level.
Before installing the beacons for the concrete screed, lay out the waterproofing and, if necessary, thermal insulation.
To correctly place the beacons, you need to screw screws into the walls at the zero level and stretch the fishing line between them without bending. This creates a guideline for level laying.
Then a small amount of solution is prepared and placed in slides along the beacon installation lines.
Next, the purchased profile is placed on these slides and set according to the level of the fishing line, while the adjustment occurs using the level. Wait for time for the solution to set and you can move on.
The distance between beacons should not exceed the value of your rule. Otherwise, it will be impossible to adjust and polish the base.
In a container, mix the components with the addition of water, and you should get a mixture resembling yogurt. The prepared mixture is laid out between the beacons and leveled according to the rule along the beacons. Laying in one room should be done in a day, and no more than three hours should pass from the start of the procedure to its end.
Then you need to leave the screed until it dries, after a couple of days the surface is watered and covered with film. Wetting is carried out for 5 days, and then left until completely dry in a non-ventilated area. At the same time, to answer the question, we can say that at least four weeks. Then, if desired, the surface is sanded.
This article discusses the issue, the screed and how it is performed. Based on this article, you can make the repair yourself.
When replacing and laying floors, concrete screed is most often used. It allows you to level the surface, make the base strong for static and dynamic loads, this is the most used flooring method in residential buildings, on industrial facilities. All known floor coverings can be laid on it, while it can protrude top layer floor.
The screed is the base for the floor covering. Most often it is made from concrete mortar, it is the finish of the base under the floor, which is made, for example, from slabs interfloor covering. Purpose of the screed:
Concrete floor screed is poured liquid composition, therefore it is classified as a “wet” screed.
What mixture will be used is determined by the future floor covering. The cement-sand composition is more convenient for use when the filling is made by hand. To use it you do not need special knowledge and manufacturing techniques. suitable for cosmetic repairs when the coating is being replaced and it is only necessary to level the base.
Separating layer for concrete screed. Classification of concrete screeds by type:
Concrete screed is used most often. To construct it, a metal mesh is used, which is covered with 4-5 cm cells. Low supports are installed throughout the floor and the mesh is laid on them. This increases strength and wear resistance. Among the disadvantages of use it should be noted:
Due to constant development construction technologies, recently fiberglass began to be used in laying concrete screeds. It is placed in a concrete solution instead of a reinforced mesh. It is a thin synthetic substance - microfiber made from polymer granules.
By making concrete more flexible, fiber fiber adds resistance to cracks. The advantage is that the use of such material is easier and more economical than metal mesh by 6 times per m2. In addition, do not forget about such a plus as the effect of reinforcement. The disadvantages include strict adherence to proportions and calculations when using the material. A mistake will turn the concrete into crumbs.
The very first thing you need to determine when pouring a screed is the thickness of the concrete layer and weight. This parameter depends on whether the concrete is laid on a floor panel or on an insulating layer, what materials are used for the mortar, and what kind of floor covering is planned.
Insulation can be different: solid or loose - the concrete layer must exceed 40 mm, with reinforcement metal mesh or fiberglass.
If the ceiling has unevenness of more than 20 mm, a cement-sand mortar using plasticizers is poured. In this case, the fill must be more than 30 mm, otherwise there is a high probability of cracking. In this case, such a layer should be in the thinnest place.
When laying floors with unevenness up to 60 mm, sand concrete is used, with a pouring height of 0.1-0.15 m. For differences of 16 cm, expanded clay concrete is first placed in the holes. This makes the floor lighter, plus - savings, since concrete consumption is reduced.
If the base is relatively flat, dry self-leveling mixtures are used. This screed is called a “layer”, the thickness of which is set by the factory. One more important parameter when laying the floor is the weight concrete pouring, which directly affects load-bearing elements. The standards establish a load of 3-4 tons per 1 m2 (the exact parameter for each building is determined in the project).
Scheme of concrete screed with waterproofing Before laying concrete with your own hands, you need to do some preparation. We use the following tools:
Materials needed for laying concrete screed:
Before starting work on pouring the base, you need to remove debris and dust. It is better to use, but you can also remove it with a regular broom. This concludes the preparation.
We mark the zero point with a water or laser level along the perimeter of the apartment. The laser level is placed in the middle; it creates lines of beam along the perimeter of the room along which marks are placed. It's a quick and easy process.
To place marks using a regular water level, you need to place a mark on one of the walls at a height of 1.5 m from the ceiling. We place the water level tube on the mark and pass it to the wall opposite so that the water inside is distributed evenly. To determine the mark zero level it is necessary to measure the distance from the ceiling to the threshold of the next room in the apartment, and it is necessary to subtract the thickness of the floor covering.
The most common way to create a smooth floor covering is a concrete screed. It can be made using mixtures of various compositions, in one or two stages. The screed can perform specific functions, have additional reinforcement, be applied to different types coatings - soil, concrete slab or wooden floors. Let's consider some types of work and technology that will allow you to carry out all the work yourself with a little effort.
Briefly described, there are four main types of screeds.
All four types can be combined with each other. Which option to choose depends on the construction conditions. However, the most common method is a simple adhesive screed.
Required tool:
Necessary materials:
The very first thing installation work begins with is a thorough cleaning of the existing coating. It is necessary to remove all debris and dirt, if possible, vacuum it. If this is not possible, work carefully with a broom, trying not to raise dust and wetting the surface.
The stage of marking the room to the level of the future floor should be done carefully and slowly. If there laser level, the work will be easier. You just need to place the device in the middle of the room and mark the resulting marks on the walls.
Working with a hydraulic level is more difficult. It's better to do it together. First, the highest point of the existing floor is determined experimentally. The rest of the screed is marked from it - one person holds the end of the hydraulic level, the second moves away sequentially along the surrounding walls and places marks at a distance of approximately 50-100 cm.
It's easy to quickly determine the highest point.
Beacons are placed at a distance of 100-150 cm from each other. The easiest way is to use self-tapping screws. Plastic stopper is embedded in a pile of mixed plaster, and with the help of a screw it is easy to adjust the height by simply twisting or unscrewing it. The uniformity of installation is controlled using a spirit level or a long rule. The lighthouse must be positioned level.
After checking each beacon and total area(the direction of setting the level is perpendicular to the beacons), you need to let the gypsum mixture dry.
If there are gaps between the wall and the floor, you need to protect the lower room from water. The perimeter can be coated with mastic, a strip of film can be laid, or cracks can be filled. polyurethane foam. Do the same if there are through holes in the floor, for example, a hole in the center of the room for lighting wires or a crack in the slab.
If the screed is made using an adhesive method on a concrete slab or existing cement-sand mixture, the base is primed. Typically, the same penetrating primer is used as for painting or gluing ceramic tiles.
In the case of insulated screeds, a layer of separator is laid for thermal protection or waterproofing. For a coating reinforced with steel wire, a mesh of rods is laid at a distance from the existing floor level. The same plaster can be used as “supports” - small piles of approximately equal height.
The mixing process is simple. The main thing is thoroughness.
First, using a trowel, carefully mix the dry ingredients. Then water is added little by little. Here you can mix using a drill and a “mixer” attachment. Add water little by little until the solution reaches the consistency of thick sour cream. If you take a handful and squeeze it lightly in your palm, a stable lump should form.
It is better to start working from the sector farthest from the door. A layer of the mixture is applied between the two beacons and carefully smoothed with the rule. At the first stage, the level is filled flush with the beacon profiles. To finish, apply a small layer that will hide them. It is better to do this work using a rule with a pen, erasing several sectors at once.
If a mixture based on cement and sand is used, it must be remembered that the drying time is quite long - about 12-14 days.
In order for the screed to gain maximum strength and not crack, you need to spray the surface evenly every day. a small amount moisture. This way the coating will acquire the best characteristics.
However, rapid drying of the screed is also dangerous. If indoors heat, low humidity or excessive ventilation, it is better to wet the surface and cover it with polyethylene to slow down drying and prevent cracks.
To level the surface and prevent the appearance of fine dust due to abrasion, final finishing is carried out. Using a circular grinding machine the surface is cleared
from small irregularities and unstable inclusions.
The minimum thickness of the screed, excluding additional conditions, is 30-50 mm. It is not recommended to make a thinner coating, even if we're talking about about thermal insulation screed for “warm floors”.
Concrete screed is very durable. This is its advantage and at the same time a disadvantage in some cases - the coating can crack. This occurs from temperature changes, and especially from shrinkage of the building or structure. To avoid such danger, security channels are made. These are cuts that are made using a stone circle and a grinder. You can use a special lath, which is laid at the pouring stage.
It is necessary to make cuts or safety channels around columns, wall projections and around the perimeter of the room. The depth should be from 30 to 50% of the thickness of the screed. You can make a grid of channels over the entire area and cover the recesses with sealant to maintain a continuous surface.
Mixtures for screed
Construction mixtures are divided into starting and finishing mixtures. The first ones are larger in size and are used to create the main thickness of the screed. The surface becomes rough and uneven. It is “brought to condition” with the help finishing mixtures, which form an even and smooth layer. This series also includes “self-leveling” screeds - this is a very finely dispersed composition that spreads and independently forms the floor level without the need for leveling.
