Density of cement-sand screed – what it is and why you need to know?

When dealing with concrete flooring, it’s important to know how dense a cement-sand screed is. The mass of the screed per unit volume is known as its density, and it has a big impact on how well and long-lasting the flooring is. Gaining the necessary strength, stability, and longevity for a variety of building projects is made easier by understanding density.

The proper mix ratio must be used when creating a cement-sand screed in order to guarantee that it can support the intended load without breaking or cracking. An appropriately thick screed offers a stable base for carpets, tiles, and other flooring materials. A low density can weaken and make the screed more vulnerable to damage. On the other hand, an overly thick screed may be too hard, which eventually causes cracks.

Comprehending the density of your screed facilitates more accurate cost estimation and planning. You can precisely estimate the quantity of materials required by knowing the right proportions, which will cut waste and guarantee a project that is affordable. Additionally, improved thermal and acoustic insulation qualities will improve the comfort and efficiency of the building in a well-mixed screed with the appropriate density.

Understanding a cement-sand screed’s density is important for both DIY enthusiasts and builders because it goes beyond simply creating a level and smooth surface. It has to do with making sure your flooring is structurally sound and performs well over time. By doing this correctly, you create a solid base for the entire project, making it safer and more dependable.

Topic	Details
Density of Cement-Sand Screed	The density of a cement-sand screed is a measure of how much mass is in a given volume. It"s important because it affects the strength, durability, and load-bearing capacity of the floor.
Why You Need to Know	Knowing the density helps in selecting the right materials and mix ratios for your project. It ensures the screed can handle the intended load and will last long without cracking or breaking.

Screed parameters for floors

The load-bearing capacity of the entire structure must be determined in order to construct a sturdy and long-lasting base for any finishing floor covering. The base of the structure is under a lot of pressure because of the large weight of the screed.

You should make precise calculations while accounting for the properties of the materials used when a composition made independently rather than a ready-made mixture bought from hardware stores is utilized to complete the task.

A necessary and reasonably easy method of leveling surfaces is cement-sand screed. It is made with sand, cement, and water. Each component’s specific quantity is determined by its properties.

Take 150 kg of sand for a 50 kg bag.

Since it is known that using cement grade M 150 is ideal, 150 kg of sand will be required for each 50 kg of this material. The moisture content of the sand determines how much water is needed.

To prepare a superior solution, take the following actions:

• 1 bag (50 kg) of cement;
• 15 ten-liter buckets (150 kg) of dry sand;
• 27 liters of water.

The amount of water in the composition will drop to 25 liters when wet sand is added.

The minimum thickness of the screed is 30 mm.

The screed must be at least 0.3 cm thick. If not, there will be a layer of cracks on the surface once the solution solidifies. Overloading the base will result from exceeding the maximum thickness of 0.5–1 cm.

The weight of the cement screed per square meter will be roughly 150 kg if this value reaches 8–10 cm. Experts advise against going over the set boundaries since this is intolerable.

The quality of the material determines the mixture’s density.

A 1 cm thick layer of cement-sand screed will require at least 20 kg of material per square meter. Its weight will be between 15 and 20 kg per centimeter in this instance.

When making a cement-sand screed, the density of the mixture must be considered. This density is determined by the materials that the artisans select.

This parameter divides the compositions into the following categories:

1. Light, the density of which does not exceed 1400 kg / m³.
2. Heavy screeds, the specified indicator of which is significantly higher than 1400 kg / m³.

If the technology is strictly followed, the sand-cement screed’s specific gravity won’t go over allowed bounds based on this sand attribute.

Universal mixture Unis Horizon Universal Fast-hardening, 20 kg

Specific gravity of the cement mixture

Cement specific gravity varies based on the type and brand

Name / brand of cement / mixture	Specific gravity (kg / m3)
M 100	900
M 150	900
M 200	900
M 300	1100
M 400	1100
M 500	1100
Sand-cement mixture	1700
Cement-perlite mortar	1000 — 1400
Cement-slag mortar	1000 — 1400

Cement frequently becomes air-enriched during transit. In this instance, right after unloading, the cement’s bulk density

1200 kg/m³ will be the value. The material will eventually start to compact and return to its typical density of between 1600 and 1500 kg/m³. Sometimes moisture seeps into the cement, causing it to become excessively dense and reach the maximum values of 3100 kg/m³. The size of the cement chips is the primary factor influencing the density variability.

It is crucial to keep an eye on this indicator when making a test material purchase. Sadly, though, determining a substance’s density is not a simple task. However, suppliers are required to follow an average indicator of 1300 kg/m³.

It is possible to compact the solution while it is being mixed. In order to accomplish this, first add coarse sand (a compaction agent) to the container, followed by medium and finer sand.

Ceresit CX 15 25 kg cement.

Minimum and maximum screed thickness

The screed layer must be at least 20 mm thick when laid on floor slabs, at least 40 mm thick when laid on a waterproofing layer, and at least 20 mm thick when laid on a heat and sound insulation layer, according to SP 29.13330.2011. When covering pipelines, including those in warm floor systems, the screed’s thickness must be at least 45 mm larger than the pipelines’ diameter. A thinner layer may cause the screed to break and become destroyed.

Experts advise a minimum screed layer thickness of 30 mm. The ideal screed thickness is between 40 and 50 mm; any more thickness means overspending on material; even when using lightweight screeds, the maximum permissible bearing capacity of the base limits the amount that can be used; and extra reinforcement of the layer is needed.

We will start our exploration of the physical characteristics of the building in question by noting that the apartment’s floor screed cannot be any thinner than 20 mm. If not, its poor wear resistance will inevitably lead to its destruction. In other words, to make it even thicker, it should be calculated at the lowest possible value.

The thickness of the screed for a water-heated floor is a totally different story. Here, the pipes should be sufficiently hidden. It’s also advised to construct an expanded clay heat-insulating pad here. As a result, the level rises noticeably.

Density of cement screed

Determining the total structure’s bearing capacity is essential to building a sturdy and long-lasting base for any finishing floor covering.

The base of the structure is under a lot of pressure because of the large weight of the screed.

When a composition created independently rather than a pre-made mixture bought from hardware stores is utilized to complete the task, precise calculations must be made while accounting for the properties of the materials utilized.

Drying time

The thickness of the cement-sand mortar layer and the outside temperature affect this parameter. Thus, a 2-centimeter layer will dry in 12–14 hours at a temperature between 15 and 25 degrees. The drying time increases with the thickness of the layer.

After finishing the work, experts recommend waiting a day or two (or longer, if the layer is large) before doing any surface manipulations.

Consumption of components

Strict adherence to the proportion on which component consumption depends is necessary to prepare cement-sand cement with the necessary strength and properties. Subject to the selection of binder grade M400, the standard (adopted in the regulations) ratio of cement to sand in cement-sand mortar is 1:3 with W/C 0.45-0.55.

• Cement – acts as a binder, usually take M400 or M500, with a production date less than 6 months ago. The fresher the cement, the more active it is and the better the characteristics it will give the mixture.
• Sand – with dense large grain, without impurities of dust and clay. Sand must be clean – this is important, otherwise it needs to be washed and dried.
• Clean water – without impurities, temperature about 20C.

The ratio of the solution’s components may vary depending on the application’s features and field. Everything is based on the brand selection.

• For masonry – use grades from M50 to M200, when working with load-bearing structures, you need to take a solution of at least M100, the installation of a prefabricated foundation requires the strength of grade M200 at least. In this case, the proportion of cement and sand is 1:2.
• Plaster – mixtures from M10 to M50 are relevant, necessarily plastic, which is achieved by introducing clay, lime dough, gypsum and other components into the composition.
• Pouring screed – from M150 and above. When mixing such a solution, it is important to correctly determine the W / C (about 0.45-0.55), since excess water can cause cracks. Classic proportions: 1:3 or 1:2.8, brand cement minimum m400.

Osnovit cement plaster RS24/1 ML 25 kg

Screed density and specific gravity of cement and sand

A cement-sand screed (CSS) can be built using a variety of materials with varying compositions, densities, and strengths, contingent upon the requirements imposed by the operating conditions:

• concrete with heavy filler;
• concrete with light filler;
• cement-sand mortar;
• dry mixes.

With heavy filler – granite screenings

The end result of producing commercial crushed stone with a fraction of up to 10 mm is a filler based on granite crushed stone screenings. Industrial construction uses concrete screed with granite filler because it is extremely resilient to frost and long-lasting. It is utilized in rooms with high operational loads, such as ground floor and basements, garages, utility rooms, and storage areas, in civil and residential construction.

Concrete made with granite screenings has a density of 1400–2200 kg/m³, placing it in the heavy series. For the given density range, the bulk weight of a 5 cm thick screed is between 70 and 110 kg per 1 m2, which is a substantial additional load on interfloor ceilings, floors with a soil or wooden base.

Sand concrete Rusean M-150, 40 kg

Light types of solutions – perlite, polystyrene, granules

In many situations, using a lightweight screed will yield better results. It is employed when installing pipelines and communications beneath the floor, when leveling removes a significant height differential, and when a screed is required to provide the floor with extra sound and heat insulation.

Depending on the type and amount of filler used in the mixture, the density of lightweight screed solutions ranges from 500 to 1800 kg/m³. Lightweight screed is sometimes used as an intermediate layer with final leveling using stronger solutions because its strength is not as great as mixtures with heavy filler.

Lightweight screeds are filled with a variety of materials, adding to the mass of the mixture to achieve different technical properties:

1. Perlite is a porous rock, has good heat and sound insulation, high absorption capacity, fire resistance, chemical inertness. For the preparation of construction concretes and mortars, expanded perlite obtained by heat treatment of the original raw materials with a density of about 100 kg / m³ is used, the density of the mixture, depending on the composition of other components, is from 400 to 1000 kg / m³.
2. Vermiculite is a natural mineral with a layered structure, expanded rock is used in construction. As a filler for solutions and concretes, it has properties and characteristics similar to perlite.
3. Expanded clay with a bulk density of 150 to 800 kg / m³, obtained by firing clay or clay shale. Its characteristics are high strength, frost resistance, chemical resistance, non -combustibility, environmental friendliness. Expanded clay crushed stone with a fraction of up to 10 mm is used as a filler or serves as a raw material for the preparation of expanded clay sand.
4. Granulated polystyrene foam (from polymer raw materials). The density of CPS based on it is from 150 to 600 kg / m³, they have a high degree of sound and heat absorption, frost resistance, but low strength compared to other lightweight solutions.

Why you need to know the weight of the screed

Consider the type of base and the room itself when determining the screed’s thickness and density.

On the base floor, a fairly thick layer of screed—between 1 and 15 cm—is applied. Because the mixture contains heavy ingredients, even a thin layer weighs between 70 and 150 kg per square meter. This will add up to a significant amount of mass.

• If a country house is on a slab foundation, the weight of the screed is not of particular importance. It is taken into account, but since the load-bearing capacity of the slab is extremely high, in fact, the design has little effect on the calculations.
• If the foundation of the building is light – strip, the load of the screed becomes a very noticeable factor. It will affect the width of the foundation. This must be taken into account even during calculations.
• In an apartment of a building with concrete and reinforced concrete floors, it is allowed to install a screed if it does not exceed a certain thickness and weight. Requirements are specified in an architectural bureau or other office. Calculates the floor structure and its expected weight based on the restrictions.
• Screed is often used to level floors on a balcony or loggia. And here its weight is of fundamental importance. If the balcony and loggia are located on a cantilevered floor slab, such a floor structure is allowed. If the balcony is suspended, screed is excluded: the balcony will not withstand such a load.
• Screed is often used to level small areas or wooden flooring on logs. Its weight is determined by the floor structure on the logs and the load-bearing capacity of the installed beams. This is important: if the coating is too heavy, the wooden floor will simply collapse.

The goal serves as the second decisive element. The coating needs to be a specific thickness if it is to level the base. Its weight has to be precisely the right amount to form this kind of thick layer. SNiP controls this criterion.

Two factors are considered simultaneously when calculating the capacity to bear the load: the material’s density and the applied pressure. Building codes also regulate this.

Rusean M-400 sand concrete, 40 kg

Types

The Knauf dry screed device is divided into four groups by the manufacturer.

Alpha

The base is pre-leveled because the Alpha variety arranges the floor without the need for expanded clay. Differences in level should not be greater than 3 cm. All that will be required for the "alpha screed" task are gypsum fiber panels, polyethylene film, and edge tape.

Beta screed

It is anticipated that expanded clay sand backfilling will be replaced by the screed. can use pores to replace fibrous and spongy materials (polystyrene foam). It is required to level the base initially. An obvious characteristic is the rise in soundproofing parameters.

Vega

Is the most popular way to put in a superfloor. The evenness of the foundation is not subject to strict requirements by the method. Backfilling makes it simple to remove any anomalies or discrepancies. A layer of gypsum fiber sheets is placed over the expanded clay backfill.

Significant savings because of the possibility of lighter building structures

Universal mixture Unis Horizon Universal Fast-hardening, 20 kg

Gamma

Distinguished by its exorbitant price. Insulation and an additional layer of gypsum fiber are layered on top of the gypsum fiber in the same manner as the "Vega" option.

Options for arranging the screed

Depending on their thickness, three types of screeds are actually used in practice:

1. The first type is a thin base. In this case, a material such as a self-leveling mixture is used, which after pouring does not exceed a height of 2 centimeters. In this case, reinforcing elements are not used.
2. The second type is a rough base, which has a thickness of no more than 7 centimeters. This layer height allows you to lay a reinforcing mesh or use reinforcement. Such a base is made for a floor structure from reinforced concrete.
3. The third type is a layer of maximum thickness, but no more than 15 centimeters, which is a monolith with reinforcement located inside it. A screed of such a height is used when it will be both the floor and the foundation of the building at the same time.

As a result, the kind of materials that will be utilized to arrange the rough floor will determine how thick the floor structure’s base is. It is not possible to utilize the minimum amount of screed if pouring concrete mortar with crushed stone added is the plan. The truth is that creating a thin base for the floor covering is not possible due to the size of the crushed stone fractions.

Self-leveling and other mixtures meant for surface finishing prior to floor covering installation are the best options for pouring a minimum thickness screed (see "What is the minimum thickness of a floor screed – standards and rules"). It is possible to create a thin, flawlessly even layer with this kind of composition.

The thickness of the screed is one of the parameters that should be carefully considered when designing a floor heating system. In this instance, the primary prerequisite is that a concrete layer completely encase the heating elements.

Given that the pipes’ standard diameter is 25 millimeters, the screed thickness needed for the structural component of a heated floor should be between 50 and 70 millimeters.

It is sufficient, according to experts, to pour a 40 millimeter layer of concrete over the pipeline to guarantee proper system operation and excellent room heating. Since most of the thermal energy from a higher screed will be used to heat the concrete, controlling the flow of thermal energy will become more difficult.

Furthermore, the mechanical impact on the room’s walls will be greater the thicker the concrete layer. Prior to adding the solution, the walls around the room’s perimeter must be adhered to with a special tape in order to prevent any unfavorable effects.

Sand concrete Rusean M-300, 40 kg

Calculation of the amount of material and proportions

Regular and ready-made mixtures are the two types used in construction. The walls are leveled as well as the floor using ordinary mortar. The most basic type of self-leveling floor screed mortar is made with clean sand that contains a medium-sized grain and M300 cement. Water makes up the third element.

To mix all the ingredients, take one part cement and add 1.5 to 3 parts medium-grained sand. However, the number of kilograms of cement taken is used to calculate the amount of water. For every kilogram of cement, 0.5 liters of water are needed.

There are a lot of modifiers and fillers available for use in construction right now that are mixed with sand and cement. For what reason do they act in this way? to shorten the hardening period, lessen the chance of cracks and delamination, and boost resistance to frost.

Common solutions are sold in construction markets, such as backfill for dry floors. By using them, repair time will be decreased. All of the ingredients in these combinations are perfectly chosen and in just the right amounts. The manufacturer creates each type specifically for a certain kind of floor connection.

The PCS consumption per square meter of screed is shown in the video.

The weight is contingent upon the relative quantities of the constituents comprising the composition, including water content, screed power, and cement brand. Generally, the screed should not be thicker than 7 cm; if it is, the house’s foundation will need to be strengthened to support such a heavy weight. The type of ligament is selected based on the anticipated thickness of the layer:

• The screed will be associated with the draft base and the walls;
• will not contact with any constructions;
• The insulating layer is used, as a result it will be a floating layer.

Universal mixture Ceresit CN 173

Varieties: cement screed

1. Calm. It is usually used in high -rise buildings – the CPS serves here in order to level the floor slabs. To perform a reliable base, a good clutch is needed – communication – a poured layer from the old. Therefore, the type of screed is called – coherent. Its minimum layer – 3 cm.
2. Incoherent. With this type of base, a new layer with the old floor is not fastened. For example, installation on the basis of concrete, which was previously polished or on a layer of insulating material. Minimum screed thickness – 5 cm.
3. Floating. If the floor needs to be made warm, it is unrealistic to achieve a rigid adhesion of the screed to the base. When the insulating material changes its size, the concrete layer above it also lowers/rises. That is why such a screed is called floating. To create rigidity, which is required, the minimum thickness of the cement-sand mass in this version of the screed is at least 6.5 cm.

While each of these CPS types has unique installation qualities, they are all connected by the use of sand-cement mortars. Occasionally, fibers are added to the composition for reinforcement in order to increase reliability. Usually, this is fiber; however, occasionally, tiny bits of steel wire are added as additives. When the concrete layer is thick, the solution needs to be reinforced.

The base’s strength is increased multiple times by the disorderly arrangement of its fibers, and cracks hardly ever occur in it.

According to building regulations, the minimum thickness of the screed is 3 cm. With the thinnest layer, during the period when the solution dries, the canvas will crack, the base will be unreliable. At the same time, concrete is very heavy: a 10 mm layer weighs about 20 kg per 1 m2. And since the minimum thickness is 3 cm, the minimum weight of 1 m2 of screed will be 60 kilos. Not every foundation is able to withstand such a load without consequences. Because of this, the foundation can settle and crack. To reduce the weight of the screed, lightweight binders are included in the solution, for example, expanded clay. The weight of 1 cm of expanded clay concrete is 16 kilos. With volumetric poured footage, the difference is significant.

Semi-dry floor screed

The relatively new technology of semi-dry screed laying offers many benefits but also presents a number of implementation challenges. In any event, attempting such a leveling on your own without any prior expertise in the field is nearly a "fiasco." particularly considering that it is nearly hard to complete without specialized tools—a grinding machine and a pneumatic mixer.

Both the semi-dry screed laying and the working mixture preparation are fairly involved processes that are obviously not for amateurs.

Traditional cement and a portion of sand that has been carefully chosen are included in the composition. Furthermore, the most common way to reinforce dry screed is to incorporate fiber fibers into the mixture.

Because there are fewer pores in the hardening solution, the finished screed created with "semi-dry technology" has an even slightly higher density. We are able to discuss the range of 2000 to 2100 kg/m³.

Cement-sand screeds, both "classic" and semi-dry, have a significant density, as you can see. When evaluating them in the context of the "corridor" that the floor slab permits following the subtraction of all other loads, the fill’s thickness stays approximately between 70 and 75 mm, but not beyond that.

However, situations can vary; occasionally, a higher floor lift that also requires simultaneous leveling is needed.

Peskobeton Master Garts Roller FC30 M-300, 30 kg

Advantages and disadvantages of semi-dry screed

Many of this technology’s benefits, which have been acknowledged by builders of all stripes, support the decision in its favor.

The benefits of semi-dry screed are as follows:

• A small amount of water added to the mixture. Almost completely eliminates its penetration into the ceiling. A reduction in the weight of the poured material is achieved.
• Reduction in the setting and complete drying time. Ability to continue work without a long break.
• Creation of a perfectly flat surface at the formation stage without the use of self-leveling solutions and additional leveling.
• Reduction to a minimum of the likelihood of cracks and shrinkage after the solution has hardened. Absence of the risk of internal voids.

There are drawbacks to this method as well:

• It is impossible to do without special equipment. It is necessary at the stages of preparation, distribution and compaction of the mixture.
• Difficulty in filling internal corners. You have to spend time and effort on this, filling such places manually.
• Minimum board thickness limit. It is 30 mm, provided that compaction is carried out with a powerful pneumatic spreader.
• Quick setting. On the one hand, this is a plus, and on the other hand, a minus, since the solution can harden without sticking to the base.

SNiP semi-dry screed

• the thickness of the semi-dry floor screed (layer height)
  , like any other, should be at least 20 mm (but even in this case, it is desirable to reinforce it with fiber fibers, otherwise there is a very high risk of cracks);
• the weight of the semi-dry screed per 1 m2
  , with its height of 50 mm, will reach about 100 kilograms (using simple calculations, you can calculate the actual indicators, and the specified mass can actually be reduced by adding expanded polystyrene granules);
• the strength of the semi-dry floor screed
  varies from M150 to M180 (excluding the addition of plasticizers, reinforcement and other impurities; the specified value is quite sufficient for most purposes, but industrial premises and areas where heavy equipment passes may be an exception);
• density of semi-dry screed
  must be within 2000-2100 kg/m3 (with standard preparation method).

Ceresit CX 15 25 kg cement.

Lightweight and lightweight screeds

This particular category of screeds "jumps out" of our purview in a way. Because entirely different materials are frequently used there as filler in addition to or instead of sand. These materials can be synthetic (most often expanded polystyrene granules) or mineral (expanded clay, slag, vermiculite, expanded perlite, loose foam glass).

But such compositions allow thick-layer leveling without the risk of creating critical loads on the floor slabs.

The lightweight "PALADIUM PalaflooR-307" floor screed has a sound and thermal insulation effect. Composition: foam glass + cement. Density should not exceed 500 kg/m³.

There is some degree of convention here, but the entire category can be separated into three subgroups:

• Ultra-light screeds with such fillers have a density of up to 500 kg/m³, but their load-bearing capacity is very low, and, as a rule, they perform exclusively insulating functions. Grade strength – usually within M5 ÷ M25
• Light screeds, with a density of 600 to 1200 kg/m³ combine both insulating qualities and the possibility of using them as a base for laying the finishing coating of a floor that is not heavily loaded. Strength – up to M50 ÷ M75
• Lightweight screeds – density from 1300 to 1800 kg/m³. Strength approaches the indicators of traditional screeds, but due to the reduction in thermal insulation qualities – there is no need to talk about any effective insulation.

Density class is a specific indicator that can be used to evaluate a solution’s (concrete’s) density for this purpose. It is denoted by the letter D, and the density in kilograms per cubic meter is the only digital value that comes after it. For instance, the density of D900 expanded clay concrete will be 900 kg/m³ when used to pour a screed.

Producers of these kinds of solutions (mixtures) are required to declare the density in the product details. This is the simplest part; all you have to do is carefully read the instructions that are attached.

Lightweight screed with "Knauf UBO" polystyrene filler. The hardened screed has a density of 600 kg/m³.

Certain compositions, like those made with expanded clay, vermiculite, or polystyrene granules, can be assembled on their own. assuming you are aware of the precise ratios and subtleties involved in blending the mixture.

SNiP dry screed

Particular consideration should be given to the option where materials meant for this purpose are laid out instead of poured into the base. Here, the standards are a little different and heavily reliant on the components utilized:

• thickness of the dry floor screed
  is directly related to the sheet covering used – chipboard, gypsum, OSB, etc. (the level of its rise should be calculated in each case separately – the indicator is determined by many factors);

Minimum (which is substantially less than the lightest version of pouring concrete, but it also depends on the qualities of the consumables used);

• the strength of the dry floor screed
  much lower than cement (but it is used mostly in residential premises, where it is more than enough);
• density of the dry screed
  should be calculated from the same properties of the sheet special material (OSB, gypsum and plywood have different values, but you are unlikely to find critical differences, because each of them was made for one purpose).

The so-called "dry screeds" are only possible with a level base; that is, it is not permitted to lay fiberboard or gypsum sheets directly on hollow-core floor slabs that have been installed with height variations and protruding mounting loops. The floor’s base must first be leveled using a standard screed. Low water resistance of dry screeds is an additional drawback. In addition to increasing thermal conductivity, saturation of gypsum fiber or fiberboard boards with water causes the slow degradation of thermal insulation materials.

Plaster Osnovit cement PRO gray 25 kg

SNiP cement-sand screed

Floor leveling cement-sand mortars are widely used in civil, industrial, and residential construction. In the latter scenario, the work is not always completed in accordance with the design documentation, and the owners frequently take on responsibility for material selection and base leveling implementation, depending on their own knowledge, recommendations from friends, or information found online. In the absence of a project, consulting publicly accessible construction industry standards is one way to guard against potential mistakes.

Document SP 29.13330.2011 "Code of rules" governs the requirements for the design of floors in buildings serving different purposes. Floors," in which the regulations in effect since 1988 have been revised to reflect the introduction of new safety requirements as well as the development of new building materials and technologies. SNiP 2.03.13–88 "Levels." The code of rules contains sections that outline general specifications for floor designs as well as for their component parts, which include coatings, interlayers, hydro- and vapor barriers, screed execution, underlying layers, and base soils.

The nature and intensity of mechanical impacts on the floor, the degree of exposure to liquids or aggressive environments, operating temperature conditions, and guaranteeing sanitary and hygienic requirements are defined by SP 29.13330.2011 as the primary criteria for making technical decisions. Special requirements are also taken into consideration for industrial premises, taking into account the unique characteristics of the facility, such as the potential for dust formation, the buildup of static charges or sparking, and the capacity for constant cleaning.

Selection of materials and preparation of the mixture

Smoothing surfaces requires the use of cement-sand screed or mortar, which is a necessary and reasonably easy method. You need water, cement, and sand to make it. Each component’s specific quantity is determined by its properties.

For instance, three times as much sand will be required if M150 cement is used. Sand is taken in accordance with the 1:5 ratio if M500 cement is used to prepare the mixture.

Take 150 kg of sand for a 50 kg bag.

Since using M 150 cement is thought to be ideal, 150 kg of sand will be required for this 50 kg of material. The moisture content of the sand determines how much water is needed.

To prepare a superior solution, take the following actions:

• 1 bag (50 kg) of cement;
• 15 ten-liter buckets (150 kg) of dry sand;
• 27 liters of water.

The amount of water in the composition will drop to 25 liters when wet sand is added.

The weight of the cement-sand screed determines the pressure that it will apply to the structure’s base. As such, it is essential to ascertain the poured layer’s thickness prior to beginning any work.

The minimum thickness of the screed is 30 mm.

The screed must be at least 0.3 cm thick. If not, there will be a layer of cracks on the surface once the solution solidifies. Overloading the base will result from exceeding the maximum thickness of 0.5–1 cm.

The weight of the cement screed per square meter will be roughly 150 kg if this value reaches 8–10 cm. Experts advise against going over the set boundaries since this is intolerable.

The quality of the material determines the mixture’s density.

Cement-sand screeds requiring at least 20 kg of material per square meter will be used when they are 1 cm thick. In this instance, the weight will be between 15 and 20 kg per cm².

When constructing a cement-sand screed, the density of the mixture must be considered; this is dependent upon the materials that the artisans will select.

This parameter divides the compositions into the following categories:

1. Light, the density of which does not exceed 1400 kg / m³.
2. Heavy screeds, the specified indicator of which is significantly higher than 1400 kg / m³.

If the technology is strictly followed, the sand-cement screed’s specific gravity won’t go over allowed bounds based on this sand attribute.

A cubic meter of sand should contain no more than 1600 kg, and its specific gravity should be between 1550 and 1700 kg/m³, as per GOST 8736-77. View this video to learn more about creating a solution:

The materials consumption can be computed with the current formula and reference data. To construct a 3 cm thick screed in a 50 m² room using cement grade M 400, you will require the following quantity of cement and sand, which can be calculated easily:

Calculate the volume of the screed. 50 × 0.03 = 15 m³.

• Volume of each component. With a proportion of 4: 1, 15_4 = 3.75 m³.
• The volume of sand will be 3.75 × 4 = 15 m³, volume of cement – ​​3.75×1=3.75 m³.
• Using reference data, calculate the specific gravity of sand – 15 × 1600 = 24000 kg, and the specific gravity of cement – 3.75 × 1300 = 4875 kg.

The water volume is calculated using a ratio of 0.5 liters to every kilogram of cement. 4875×0.5=2437.5 l will therefore be needed.

You can complete the task quickly and effectively by adhering to all requirements, which will also establish a solid foundation for the finishing coating.

Plaster Osnovit cement RS24/1 ML 25 kg

What factors affect the consumption of the mixture?

Actually, the working solution is the cement-sand mixture (assuming water and other modifying additives are ignored). As a result, the amount of mixture used is mostly determined by the scope of the project and the requirement for the solution.

The following factors impact the cement-sand mixture’s weight:

• the proportional ratio of sand to cement (the higher the proportion of cement, the heavier the mixture);
• the properties of sand (sand with large particles will be heavier than fine sand).

The working consumption of the cement-sand mixture already depends on the specific type of work and its features. For example, the consumption of the mixture for floor screed depends on the thickness of the screed. As the thickness increases, you will need more mortar, and therefore more cement-sand mixture.

• Cement D0 and D20: characteristics and scope of application
• Cement with sawdust

When UPS is used: layer height

After determining the number of components required, it is imperative to elucidate the rationale behind the varying layer heights. The latter is directly influenced by the preparatory layer’s goal:

1. Binding element. Necessary to fasten the subfloor and walls. Up to 4 cm.
2. Separate element. Is the base for the floor covering. Up to 5 cm.
3. Floating slab. If the mixture area is separated from the walls and floor by another layer. From 5 cm to 7 cm.

Underfloor heating screed

The coating’s weight is impacted by height. As a result, it’s critical to evaluate the base’s capabilities and requirements carefully. Look for other ways to level if you are unable to combine them.

There is a list of circumstances where using cement-sand screed is appropriate:

• use of water or electric underfloor heating;
• only a subfloor;
• the need to create drainage and water drainage systems;
• strong relief of the coating.

The coating can be strengthened by screed reinforcement. Although it is not required, it is advised to guarantee strength.

What and why to reinforce the screed with?

By reinforcing, the screed’s quality characteristics can be improved. You can use a metal mesh or fiber for this.

• Reinforcing, metal mesh is used more often than fiber. A welded mesh made of 4-5 mm rods is suitable, which is produced in rolls or sections. The second option is reinforcement rods with a cross section of up to 12 mm, fastened with wire. This will provide additional strength, but reinforcement rods will cost more than a solid mesh. The mesh is usually laid with an overlap, so it is taken 20-30% more than the total area of ​​​​the room.

Crucial! Reinforcement with rods or mesh increases the screed’s weight significantly. Furthermore, the minimum layer of the screed increases to 30 mm, though this is not always possible to implement.

• Fiber for screeds began to be used not so long ago as metal meshes, but it is already quite popular. This material is thin polypropylene fibers 3-18 mm long. It is added directly to the solution (before adding water) in the required amount. It is easy to use, resistant to mechanical damage, waterproof, not very expensive and not heavy, like reinforcing mesh. Fiber consumption – 0.6-0.9 kg / m3. cube of solution.

A picture of the floor’s reinforcing mesh

For both homeowners and builders, knowing the density of a cement-sand screed is essential. This measurement has an impact on the flooring’s overall performance, strength, and durability. In order to ensure that your floor can withstand the weight and wear of regular use, a denser screed offers better support and longevity for a variety of flooring types. By choosing the appropriate mix for your project, you can achieve a smoother, more dependable finish by being aware of the density. Whether you’re building new or remodeling, understanding this idea will have a big impact on the caliber and longevity of your flooring.

Leveling the floor with dry screed: subtleties and special nodes

It ought to be obvious what a dry floor screed is. Although the technology is very basic, some things are not "just like that" clear.

These are the Knauf profiles and the corresponding rule for dry screeds.

Procedure for performing work

Setting up the base is where you need to begin.

In order to accomplish this, the previous floor covering is removed from the floors, construction debris is cleared from the room, and construction beacons are installed in order to use a level to determine the horizon.

Any room where the base temperature does not drop below +5 ˦C can be configured with sand-cement screed.

After installing the beacons, start the screed pouring process from the farthest corner.

The waterproofing layer, which may be made of polyethylene film, is laid down before the beacons are installed. The canvas’s edges are brought up against the wall until they extend to the screed’s level.

If the room has a door, make sure that it is not blocked before starting to pour the screed in the most difficult-to-reach areas.

One strip of the base is filled with the prepared mixture once the solution containing the beacons has solidified. Once the first strip is ready, level the solution using a rule and start pouring the solution into the second. Once the 12 hours have passed, take out the beacons and fill the empty space with a solution that will take approximately 15 hours to solidify.

Proceed to prepare the grouting mixture and carry out the necessary surface manipulations. A dry or wet mixture made of equal parts cement and sand is required. Using specialized tools or by hand with a floor grater or polisher, grind the surface. Watch this video to witness every step of the concrete pouring procedure on beacons:

Once everything is finished, you will have a somewhat uneven but smooth surface that needs to be rolled up with a wet roller and covered with polyethylene film. After soaking the screed for a minimum of seven days, remove the film.

Tools for work

In order to save time later on when searching for containers or pouring out components "by eye," you should ideally prepare the tools ahead of time and have everything you need on hand before beginning to make the solution.

• Mixing container – pallet or concrete mixer, large rectangular bowl (trough). It is best to choose a concrete mixer, since the pallet is difficult to work with, and individual components can be collected in a container with corners.
• Shovel – for laying components.
• Bucket – used as a measuring container when determining the volume of components.
• Construction mixer or drill for mixing the composition (if you are preparing a little).
• Construction cone – can be useful for determining the level of mobility of the mixture.
• Tools for performing work – rules, trowels, spatulas, etc.d., the set depends on the task.

Display of beacons

Screed installation can be expedited and quality assured by strategically placing beacons throughout the room. Consider attaching beacon profiles to alabaster as one of your options. The first beacon should be placed next to a chosen wall, and the second one should be placed across from this wall. They have to be positioned precisely in accordance with the level in this instance.

What matters most is that the beacon’s height does not exceed the floor’s future level. The distance between the elements must be fixed in steps of 40 to 80 cm. Some individuals check the beacons’ horizontality by stretching a mesh of threads along them. This facilitates the process of leveling the solution across the room’s surface.

Adding reinforcing elements to the screed will increase its strength. Prior to installing the actual solution, this is completed. It is better to use a liquid solution that can fill in all the gaps and voids before pouring the mesh. It is not necessary to stretch it tightly; instead, spread it out evenly across the plane. Thanks to its protection from the elements, the sand floor screed will grow more dependable and long-lasting.

It’s a different story to set beacons for dry floor screed. It’s hard to find branded ones—those used by business representatives. They are nonexistent, that’s all. Usually, plasterboard profiles are used in their place. They cooperate with them in this way:

• The profiles are laid out on piles of expanded clay backfill, pressed down, setting them to the desired height. The distance between the profile-beacons is slightly less than the length of the rule.
• Expanded clay backfill is poured between the beacons.
  The most difficult thing when making a dry floor screed is to level the expanded clay and prevent dips and voids
• Take a long rule or just a flat bar. It is supported on the beacons, pulling and leveling the backfill layer. If holes form somewhere, they are filled in, pulled again with a rule.
• After the backfill is leveled, the profile is removed, the hole is filled and leveled. In this case, you need to move along the gypsum fiber sheets that are laid on the leveled layer. You cannot step on the expanded clay.

You must somehow possess sophistication. Generally speaking, it appears straightforward and easy until you actually do it. There is no security on the beacons; if you push on them a bit more, they disappear. You must exert control over the force and continuously monitor if the level has dropped or the bar has moved. It is still easier if you have a laser level. If not, it is quite challenging.

Options for installing beacons

Gypsum fiber board deflection will be problematic if beacons are placed atop flat cakes. Deflections will result from the thinner layer of expanded clay above these "piles." One option is to screw in the studs and adjust the screws based on your height. They have hook platforms that the profiles can rest on. Following alignment, the platforms will also need to be deleted in addition to the profiles. It would also be very beneficial to remove the screws. This will be the best choice.

There is yet another option, but it is suitable for rooms that are not very large. The guides require a special rule to be made because they are screwed to the walls. In chronological order:

• We screw the profiles to the walls at a certain height. Obviously, they must be aligned in the horizontal plane.
  Here is the guide on the wall. Also, at the same level we fasten on the second
• Take a long flat board, a piece of thick polymer. It is important that the strip is level, without deflections. If there is any defect, it must be eliminated. We make cutouts on the sides so that the strip can slide along the guide beacons. The cutout must be such that the lower edge of the strip installed on the beacons is at the level to which the backfill must be leveled.
  This is a non-standard option: beacons for dry screed are screwed to the walls
• We pour the backfill, starting from the far wall at a distance equal to two or three times the width of the gypsum fiber board or superfloor. We leveled the backfill level at a certain distance.
• We laid the gypsum fiber board sheets, smearing the joints with glue.
• We installed self-tapping screws (can be postponed for later).
• We filled it again with expanded clay at a certain distance.

And this is how a rule for wall-mounted beacons should be made. Working in this manner is far simpler. First of all, you can be sure that the rule is in effect. It’s not necessary to continuously monitor the location of lighthouses. Secondly, it is less difficult to lay sheets from the ground than it is to balance on them. Thirdly, once the floor is completely installed, you can tighten the screws. Fourthly, the beacons don’t impede the process in any way because they are taken out after the sheet material is installed.

In construction projects, knowing the density of a cement-sand screed is crucial to getting the desired results. Density has an impact on the screed’s overall performance, strength, and durability. Building professionals can make sure the screed can sustain loads and endure daily use wear and tear by knowing its density.

A more effective and economical building process can be achieved by choosing the appropriate materials and mixing ratios with the aid of accurate knowledge of screed density. For the construction to last a long time and be safe, it guarantees that the screed has the proper consistency and structural integrity.

Furthermore, knowing the density facilitates improved resource management and planning. More accurate material quantity estimates enable builders to cut costs and maximize resources. In addition, it helps ensure that construction adheres to industry standards and building regulations.

In conclusion, understanding a cement-sand screed’s density is essential to using good building practices and goes beyond simple technical information. It affects the project’s economic viability, quality, and sustainability. This information is crucial for anyone working in the construction industry, from builders to architects, in order to create dependable and long-lasting structures.

Video on the topic

Cement-sand screed, to do it or not .

Acceptance of the apartment How to check the cement-sand floor screed? What the developer saves on?

Floor screed what the customer should know

Tightening the screed with tile adhesive.

Workdays (installation of cement-sand screed)

THIS IS WHY THE SCREED CRACKED!