Filling of floor screed in an apartment or industrial premises is a mandatory procedure. The topcoat is laid on a leveled base or it is used without finishing as a working surface for industrial production. Before deciding how to calculate the amount of cement for floor screed, you need to find out the purpose of the room and the estimated load on the concrete base.
One of the main criteria in preparing a solution for pouring a base is its thickness. It should be remembered that reinforcing with a metal mesh is carried out with a minimum base thickness of 20 mm, a maximum pouring height of 40 mm, and it is this thickness that is most often used for flooring in civilian housing construction.
The next important point for the calculation is the brand of cement. To organize the foundation, cement of brands M300, M400, M500 is used. As a result of mixing with sand and water, a cement mortar with a value of M150 or M200 is obtained.
The brand of the mixture is determined based on the planned load on the base. So M200 can be used to organize the foundations in industrial buildings, for example, in garages, and the strength of the M150 brand is sufficient for pouring screed in the apartment.
For calculations, you need to know the rate of cement consumption to obtain a solution of a certain brand. So, to obtain one cubic meter of M150 grade mortar, 330 kg of M500 cement or 400 kg of M400 cement will be required. To get the same volume of brand mortar, M200 you need to purchase 410 kg of cement M500 or 490 kg of cement M400.
Let's calculate the organization of the base with a thickness of 40 mm for a room of 30 sq.m. in two versions: for M150 brand mortar and for M200 brand using M400 brand cement. Calculation procedure:
- First you need to calculate the fill volume in cubic meters. To do this, you need to multiply the area by the thickness (30x0.04). It turns out a solution volume of 1.2 M3.
- Given the rate of cement consumption per 1 m3 for mortar M150 and cement M400, we get: 1.2 m3x400kg = 480 kg. The weight of one bag of cement is 50 kg, which means it will take 10 bags.
- Given the rate of cement consumption per 1 m3 for mortar M200 and cement M400, we get: 1.2 m3x490kg = 588 kg, which corresponds to 12 bags.
- The amount of sand is calculated from a ratio of 1: 3, which means for a solution of the M150 brand, it will be necessary to acquire: 480x3 = 1,440 kg of sand, and for a solution of M200: 588x3 = 1,764 kg.
- A volume of water is added gradually until the desired plasticity of the solution is obtained.
For the work on the organization of screed in the apartment, river sand is used, for production premises sand is selected from quarries.
This model of calculating cement consumption for floor screed is applicable for any area and thickness of the mixture laying layer. To obtain the area of the room, the length and width of the room are multiplied.
If the configuration of the room is complicated, it is best to use the floor plan and calculate the area, checking with paper. Thus, given the ratio of 1: 3, it will be possible to determine how much cement and sand are needed per cube of mortar for screed.
For dry mix
When using dry and semi-dry mixtures for screed, it is necessary to take into account the characteristics for each specific mixture, which can be found on the packaging. Usually indicate the volume of the mixture to cover one square meter of the base with a layer of 1 mm. For example, to obtain a solution of the M100 brand, sufficient for indoor use, a manufacturer of semi-dry floor screeds recommends the following consumption:
- mixture consumption 2 kg per square meter with a screed thickness of 1 mm;
- water consumption of 0.22 liters per 1 kg of the mixture.
Given the above data, you can calculate the required material for 30 square meters with a screed thickness of 40 mm.
It is necessary to multiply the area by the mixture consumption by 1 m2 and by 4 (since the planned thickness of the screed is 4 mm, and the calculation is given for a thickness of 1 mm). We get: 30x4x4 = 120 kg, while the volume of water required: 120 kg x 0.22 l = 26.4 liters.
For a traditional solution
The traditional calculation of building materials for the production of ordinary cement-sand mortar is carried out in cubic meters, so for ease of calculation, you need to convert cubic meters to kilograms.
For example, for an area of 30 sq.m. and a screed thickness of 40 mm will require 1.2 m2 solution. In this case, the volume of cement will be one fourth of the total volume, and sand - three fourths.
It turns out that cement will need 0.3 m3and sand - 0.9m3. The estimated number of kilograms of cement in one cube is 1300 kg, and sand - 1625 kg.
As a result, to obtain 1.2 m3 mortar, you need cement 0.3 m3h1400kg = 420 kg and sand 0.9 m3x1625kg = 1463 kg.
The required volume of water to obtain 1.2 m3 the solution is calculated at a rate of 0.4 liters per kilogram of dry components, which is (420 + 1463) x 0.4 = 753 liters.
What the expense depends on
The calculation of the cement mortar for pouring the screed depends not only on the concrete grade that is planned to be obtained, but also on other factors. Ideal calculations were given above, but in real life various changes and corrections arise:
- Examples of how to calculate cement for screed are true for fresh cement, but if material produced more than six months ago is obtained for work, the strength of concrete with its use will be significantly lower. Therefore, the volume of cement in the mixture is increased by 10-15%;
- If the measurements of the height of the future screed were determined incorrectly or if there are significant defects in the base, the volume of cement-sand mortar can increase up to 50% of the calculated volume;
- To save on the production of screeds, as well as to ensure the thermal insulation properties of the base, additives can be used in the mixture of large fractions, and the thickness of such screeds can reach 10 mm. Expanded clay, shungizite or crushed stone are usually used as additives, but such materials significantly change the properties of concrete and can affect the durability of the screed;
- When placing communications at the base of the screed, a change in volume occurs, which affects the amount of materials for preparing the solution for pouring the screed;
- The amount of material used depends on the brand of cement used and the required strength of the resulting solution;
- When pouring some rooms, a requirement may be provided for organizing the slope of the screed, in this case, the volume of the solution and the materials for its manufacture also change.