7 tips for choosing and calculating

8 min


If the theater begins with a hanger, then renovation in an apartment – from the alignment of all surfaces. Probably, it will be superfluous to tell what sad consequences a crooked floor can lead to. In order not to have any problems with laying decorative coverings and installing furniture in the future, you must take a very responsible approach to the process of leveling the floor. Previously, for this purpose, a mixture of sand and cement, prepared by hand, was used. The process was laborious, long and dusty. Now everything has become somewhat simpler, because a dry mix for floor screed has appeared on sale, and of different types. Let’s try to figure out why it is better than classic hand-made mixes, and which mix for floor screed is better to use in certain cases.

# 1. Pros and cons of dry mixes for screed

How was the floor screed done before? Three to four parts of sand were added to one part of cement grade M400. It remained only to dilute the resulting mixture with water and pour it over the floor. A more advanced method involves the addition of plasticizers and fiberglass to improve the characteristics of the mixture. Many people still use this technology, despite its many disadvantages. Not only is it heavy and dusty, but it will also have to mix a huge amount of mortar, so it will be difficult to do without a concrete mixer. A problem may arise with the purchase of 100-300 kg of sand, since most sellers sell it at least by a ton. These are not all the difficulties faced by those who want to save on screed and do everything with their own hands.

You can overpay a little and buy a dry mix for floor screed. In it, all the components are already dosed in accordance with the optimal proportions, and you just have to add the specified amount of water, mix the mixture using a drill with a special nozzle and equip the screed. Saves time, nerves and energy.

The main advantages of dry mixes for screeds include:

  • ease of preparation. The manufacturer did the most difficult and responsible part of the work for you – he mixed all the components in the correct proportion;

  • ease of mixing. After you have added the amount of water specified by the manufacturer, it remains to mix everything with a construction mixer or drill from the appropriate nozzle. No special equipment, no concrete mixers – everything is simple and affordable;

  • almost anyone can perform a screed using dry mixtures – no special professional skills are required for this, and all the basic steps and tips, as a rule, are even set out in the instructions on the package;
  • Transporting dry mix bags (typically 25 kg) is much more convenient than large bags of cement, buckets or trucks of sand;
  • the consumption of a screed made from a dry mixture is less, which means that the load on the floors will be lower. It is possible to achieve a reduction in consumption per 1 m2 due to the precise dosage of all components and the introduction of additional substances;

  • it is difficult to arrange an ordinary screed with a thickness of less than 30 mm, since during the drying process such a base can crack and collapse. In the case of dry mixes, you can get a screed with a thickness of only 5 mm, and in terms of its main properties, it will not be inferior to the classical analogue. The reason is stated in the previous paragraph;
  • the curing time is shorter than that of classic screeds, since the composition includes special modifying substances that accelerate this process;

  • a huge selection of ready-made compounds, so you can choose the most suitable solution for dry and wet rooms, as well as find a screed that will dry record quickly or have self-leveling properties.

The disadvantages usually include the cost and the inability to control the components used by the manufacturer. As for the price, it is not that high, especially when you take into account all the many amenities. With the quality of raw materials, it is more and more difficult, so it is better to take the products of proven brands that have been working in this area for decades. The company “Lentekhstrom”, for example, has been operating since 1995 on the market of St. Petersburg and the region, produces and sells dry mixes for screed under the trademark “Polygran”, the assortment can be found on the page https://ltsr.ru/stroitelnye_smesi/tsementno_peschanaya_styazhka_pola/… Over the years, the company has established itself as a reliable manufacturer and seller who does not pursue superprofits, therefore it offers customers reasonable prices for all products.

# 2. Types of dry mixes for floor screed

The range of mixtures is really huge, but all the variety that manufacturers offer us can be divided into two large groups:

  • cement mixtures are made on the basis of different brands of cement. Depending on the brand, as well as on the fillers and modifiers used, compositions with different properties are obtained, which are used at different stages of surface leveling;

  • gypsum mixtures are made, as you might guess, on the basis of gypsum, are used less often, despite the low cost, as they are demanding on operating conditions.

https://youtu.be/L8VR7Ck1otE

No. 3. Cement mixes for floor screed

The cement mixture is more expensive than gypsum and dries longer, but it is almost universal and can be used in any premises: living and bathrooms, apartments and shops.

Depending on the composition, the following types of cement mixtures are distinguished:

  • mixtures for rough leveling are made using coarse sand, granite chips or even fine expanded clay. Such compositions are used when the base difference is significant and it is necessary to make a screed of impressive thickness. Experts use similar mixtures to equip screeds from 30 to 80 mm. In the end, although the surface is leveled, it does not become smooth, so that one more layer of screed (finishing) cannot be dispensed with, especially if a covering, such as linoleum or laminate, is laid. If ceramic tiles or porcelain stoneware are used, all irregularities will be leveled out during the application of glue, so that you can do without the finishing layer of the screed and save money. Such compounds can even be used outdoors as a stand-alone coating. They are also suitable for installation over the underfloor heating system (it is undesirable to only use a mixture with expanded clay). If it is necessary to level the floor with a difference of more than 80 mm, then it is still better to use concrete, since the mixture in this case will be an extremely uneconomical solution;

  • mixtures for finishing works contain fine sand (fraction up to 0.6 mm) and plasticizers. Such a composition allows you to get a perfectly flat and smooth base, which is suitable for laying any type of facing material. The mixture is used when it is necessary to create a screed with a thickness of 4-5 mm to 10 mm. Such mixtures are often called self-leveling floors. If it is necessary to strengthen the screed, then you can additionally use a reinforcing fiberglass mesh or immediately take a mixture containing fiber. It makes sense to use such fortified compositions when a really increased load on the base is expected, otherwise there is no point in overpaying;

  • self-leveling mixtures contain filler with particles less than 0.3 mm and special additives. Due to this, the finished composition has excellent fluidity and the ability to self-level under the influence of gravity. Such mixtures are used as a finishing base, the recommended layer thickness is up to 5 mm. This screed dries quickly, gives an excellent result with minimal effort, but is more expensive than other types;

  • mixtures for underfloor heating are produced using plasticizers, which, during the hardening of the screed, “expel” all air bubbles. The latter are a kind of heat insulators that prevent the flow of heat from the heated floor into the room. It turns out that the thermal conductivity of the screed increases in a similar way. In addition, these compounds can boast of high plasticity and inertia, which is important with frequent temperature changes. Of course, when arranging underfloor heating, other types of screeds are also used, but in order to get an effective system, it is better to use a special composition.

No. 4. Gypsum mixtures for floor screed

Gypsum compositions are used less often than cement ones, their lack of versatility is to blame. Produced on the basis of finely ground gypsum mixed with various mineral fibers and sand. The main advantages of such formulations include:

  • high drying speed;
  • high strength;
  • small price;
  • environmental friendliness, no dust during cooking;
  • high rates of heat and sound insulation.

The main disadvantage is that gypsum mixtures are not resistant to moisture, so they can only be used in residential premises. Experts say that gypsum composition is ideal for screed wooden floors, since such a base can effectively regulate the level of humidity, keeping the wood in its original state for a long time.

Gypsum screed will dry for 14-15 days, cement screed – 25 days. During this period, it is impossible to carry out further work on the cladding. If there is no way to wait, then use the dry screed technology. To do this, use a backfill based on expanded clay crumbs or polystyrene granules. The material is rammed and aligned with the beacons, sheet material is laid on top (drywall or OSB-board). No water is used, so waiting for everything to freeze is unnecessary. The next step can be started instantly.

No. 5. Calculation of dry mix for screed

Perhaps the question of cost worries us sometimes even more than the quality of the screed obtained. The price depends on how many bags of the mixture you need. It is not difficult to calculate this number. The procedure is as follows:

  • we determine the floor area and the thickness of the layer of the future screed. The last parameter depends on the degree of roughness of the underlying surface. Let’s say we will perform a screed in a room of 3 * 4 m (area 12 m2), and we need a layer 13 mm thick;
  • we carefully study the packaging of the selected mixture and look for the mixture consumption parameter. The manufacturer usually indicates the consumption in kg per 1 m2 with a layer of 10 mm. At this stage, you can study the declared characteristics of several mixtures and compare the results obtained. Some unnamed companies (read unscrupulous fly-by-night manufacturers) may deliberately lower costs. For example, let’s take a mixture of Bergauf Base with a consumption of 22 kg;
  • if the consumption of the mixture is 22 kg / m2 for 10 mm of the screed, then with a layer of 13 mm, 1.3 times more of the mixture will be needed (13/10 = 1.3). For 1 m2 of screed, we will take 22 * ​​1.3 = 28.6 kg, and the whole room will take 28.6 * 12 = 343.2 kg of the mixture. Just in case, it is better to add a margin of 5%. You get 360.36 kg of the mixture;
  • dry mixes are sold in bags of 25 and 50 kg. The Bergauf Base taken as an example is supplied in 25 kg bags. You will need 360.36 / 25 = 14.4 bags, round up and buy 15 bags of 25 kg each. Should be enough. The average cost of one bag of such a mixture is 230 rubles, i.e. 3450 rubles will be needed, and for example, we have taken far from the cheapest composition.

No. 6. Major manufacturers

The manufacturer is responsible for the quality of its products with its reputation. If you want to be sure of the correct proportions and the adequacy of the specified consumption, then it is better to buy mixtures from trusted manufacturers. Among the largest, we note the following:

  • Knauf is a German company that, among other things, produces dry building mixtures. For screed floors there is a cement and universal gypsum-cement self-leveling screed. The cement composition costs about 500 rubles. over 25 kg;

  • Ceresit produces a wide range of cement and gypsum compounds. The universal composition CN 175 will cost about 400 rubles. for 25 kg, and self-leveling mixture DD for creating a screed with a layer of up to 5 mm – 850 rubles;

  • Bergauf has a wide range of solutions for roughing and finishing floors. For basic leveling, mixtures Base (about 230 rubles per 25 kg) and Erste Grund are suitable, for finishing you can use Easy Final (300 rubles) and Boden Nivelir, there are self-leveling mixtures;

  • “Osnovit” is one of the most famous domestic manufacturers, it produces rough, finishing and high-strength compounds, as well as mixtures for use with warm floors. Prices are reasonable. A 25 kg bag of FC44 M mixture costs about 175-220 rubles;

  • Unis offers the widest range of floor screed mixes. There are rough and finishing compounds, reinforcing and fast-hardening compounds, as well as self-leveling and high-strength compounds. A bag of 25 kg of mixture for roughing works will cost 205 rubles.

It is also worth noting the products of the brands Ilmax, Ivsil, Poligran and Sarmat. It does not interfere with looking on the Internet before buying and reading reviews about a specific composition of a certain manufacturer.

No. 7. The procedure for filling the screed

Working with dry mixes is very simple, the procedure is as follows (you can read more about the definition of the zero level and the specifics of the work in this article):

As you can see, everything is simple – even a non-professional can handle it.

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Steve

Passionate about DIY for over 10 years and all the new tools, I give you through this blog all my advice, tips, tests in all areas: carpentry, electricity, masonry, gardening, home automation ...

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