Rules for caring for a semi-dry floor screed: how long it dries and how to check the humidity?

If you’re searching for a flooring option that is both quick to dry and durable, semi-dry floor screeds are a popular choice. With its quicker drying time, this technique offers the advantages of conventional screeds, making it perfect for both residential and commercial projects. However, proper care and monitoring during the drying process are essential to guarantee the longevity and quality of the screed.

Recognizing the drying time of a semi-dry floor screed is one of the most crucial aspects of its maintenance. Semi-dry screeds dry much faster than traditional screeds, which can take weeks to fully cure. However, a number of variables, including the screed’s thickness, the surrounding air temperature, and the relative humidity, can affect how long the drying process takes. You can ensure best results and more accurate drying time estimation by keeping an eye on these conditions.

Checking the humidity levels in your semi-dry screed is another important part of maintaining it. Sufficient humidity levels are necessary to prevent problems such as uneven drying or cracking. Your screed’s humidity can be measured using a variety of techniques, from straightforward plastic sheet tests to more sophisticated moisture meters. You can make sure the screed is drying evenly and prepared for the next steps of your project by conducting routine checks.

You can get a high-quality finish with your semi-dry floor screed by attending to the drying process and adhering to these basic guidelines. Gaining an understanding of these principles will help you, whether you’re a professional contractor or a do-it-yourself enthusiast, get the most out of your flooring project.

Need for special care

A semi-dry screed’s solution is heavier because it is thicker and denser. Applying the mixture to the surface is akin to backfilling in that the dense material is released and placed on the ready surface.

Use specialized machine equipment to achieve such consistency. Tension is created in the binding ingredients within the solution by a small amount of water (approximately 25% to 25% of the total volume) and a large weight, while the mixture dries more quickly.

Because of the increased propensity for deformation phenomena, peeling and weak hardening are possible, which is why it’s critical to reduce moisture evaporation.

The precise timing of the drying and hardening processes (gaining strength) is especially important, and this is accomplished by establishing an ideal microclimate that is moistening the mixture and stable with adequate air humidity and temperature. That is to say, in our situation, the weather matters more than wet screed.

When air humidity and temperature fluctuate, there are:

  • delta;
  • chips;
  • cracks;
  • height differences;
  • bulging.

That’s also the reason semi-dry screed is spread using:

  1. fiber;
  2. with plasticizers;
  3. strips with compensation gaps, which are especially important if there is a warm floor underneath.

Because semi-dry screed shrinks very little, it is less likely to crack or become uneven. Since there isn’t any extra water present, porosity, uneven drying, and void formation are not possible. However, there is a feature that negates this benefit almost entirely: quick drying, which can cause peeling in particular.

To slow down this process, it is advised that the thickness of such a coating be at least 4-5 cm due to this subtlety. Speedy hardening makes the composition stronger and helps with even load distribution, but it will become weak and brittle and peel if it dries before it has a chance to adhere firmly.

Ensuring that a semi-dry screed dries out prematurely and remains uniform is crucial. This can be accomplished by establishing and preserving a microclimate that is stable.

Cement hydration requires a specific temperature and humidity level in the mixture as well as in the air, and it must happen gradually and without jerks. This is particularly important in a semi-dry screed because of the quick drying (less water). Making sure this process doesn’t end before hardening is crucial.

Islands of accelerated composition expansion will form on the floor if the conditions are broken and the liquid is distributed unevenly (this can also happen if you add more than is usual). The surface will bulge and hump.

Understanding a semi-dry floor screed’s drying process and making sure the proper humidity levels are maintained are essential for optimum results. Normally, the screed dries in 7 to 10 days, but this can change based on the surrounding circumstances. You can use a straightforward plastic sheet test to determine the moisture content to see if it’s ready for the next stages of construction. Taking good care of the drying phase guarantees a strong and level foundation for your building project.

What and how affects the curing time?

The primary guideline states that the screed must dry slowly and steadily, or in quiet circumstances free from drafts, temperature fluctuations, and humidity changes. Let’s take a closer look at the various aspects that influence semi-dry floor screed.

Temperature

Must not be hot or cold, but remain steady within a specific average range. It is never acceptable to allow the drying process to proceed more quickly than necessary when the values are abnormally high.

More water evaporates, severely deforming the mixture and causing cracks to form. The solution also dries out too quickly, becoming weak and brittle.

Freezing will happen at negative values, which will also cause the aforementioned humps to appear. Working only in positive temperatures starting at +5 °C is required.

Humidity

Low air humidity (60–70% is the recommended range) will hasten drying, which is highly undesirable because it will draw moisture from the mixture intensely. The effects are the same as when the temperature is too high.

However, in this instance, high humidity is perfectly acceptable—it is practically negligible within acceptable bounds and even helpful, as it is preferable for the mixture to dry a little more slowly than more quickly. Additionally, the screed is moistened in the early days to a slight extent; this procedure is not only possible and advised, but also required (though, in certain situations, if the environment is "wet," you can omit it).

However, this is usually only noticed when the house is on wet soils and in the same climate. On the other hand, if an increased parameter makes residual drying impossible, then this is not good. The vapor barrier primer solves the issue.

Temperature and humidity variations are frequently riskier than departures from the norms of environmental parameters within reasonable bounds because of the periodicity with which they cause tension to weaken or increase and expansion to contract, aggravating damage, cracking, the appearance of unevenness, and fragility.

Drafts

A draft is one of the risky elements that can lead to changes in environmental parameters, so it must be avoided.

Materials such as these that absorb moisture speed up the drying process:

  1. sawdust;
  2. dry cement;
  3. gypsum;
  4. simple wooden boards and the like.

The listed should not be in the same room as a result.

Other factors

Adversely impact base compositions that evaporate chemicals to an extreme degree.

Water can be present because, in this case, increased humidity within acceptable bounds during the hardening period is regarded as normal. If the microclimate is excessively dry, dishes containing water may occasionally be placed on the site.

Under normal circumstances, semi-dry screed’s maturation and drying shouldn’t be sped up. The only way to slightly alter the microclimate is to humidify the air and, if the temperature drops below -5 °C, turn on the heating (heat flows should be directed toward the ceiling). All of these adjustments should be made smoothly and without abrupt movements.

The master’s job is to maintain stability and an ideal balance of the environment’s features while tending to the screed after it has been poured. In this instance, hardening will undoubtedly occur within the suggested time range and be of the greatest caliber; drying will not surpass this process.

Small variations in humidity and temperature can cause the screed’s maturation time to vary slightly. As long as these variations stay within acceptable bounds, meet recommended standards, or even slightly deviate from them, this is acceptable. Either way, a slower drying time for the base is preferable.

Materials and tools for maintenance

What the screed needs to be given in order for it to mature, harden, and dry is:

  • Covering material. Usually, polyethylene film of 80-100 microns is used, a thinner, less flexible material is also suitable, but it is not very comfortable when laying. Agrofibre, any fabrics (except synthetic completely sealed, without absorption properties) are not suitable, since they "breathe", absorb moisture. Can be covered with plastic sheets and similar, but the material should be as lighter, dense, smooth, even. Edges, edges of the screed should also be covered. The film can be pressed with light wooden planks, but their weight should be small enough to not leave any traces;
  • Moisturization devices During the first few days of drying. This can be done manually, but uniformity and not abundance are important here, therefore the best effect is achieved precisely by spraying, spraying water. Ideal for this measure are manual or automatic (with an electric pump) spray guns, spray guns; in extreme cases, you can moisten an ordinary broom;
  • Water at room temperature or the same temperature, like the medium being served, you can take it a little warmer, but only a few degrees, to avoid rapid evaporation, which deforms the mixture. A liquid that is too cold will penetrate the solution more slowly and be distributed unevenly in it;
  • Moisture meter. To find out how drying occurs under certain conditions, and whether they need to be adjusted. The analysis will show whether it is still necessary to wait or it is already possible to lay the floor covering, whether additional measures should be taken in the form of individual drying, vapor barrier primers. You can also determine the level of this parameter using folk methods – spread a paper napkin on the surface. But this method provides only limited information: if the material is wet, then the screed is still drying, if not, then you need to wait a few more days. That is, it is difficult for them to track the detailed dynamics, the speed of the process, and this is important in some cases, since exceeding the permissible value even by 1% can cause the floor covering glue to hold poorly, mold, fungus, deformations on sensitive materials, for example, on parquet. However, if the napkin is completely dry, then with some confidence we can say that the base is ready;
  • Shoe pads. It is not recommended to walk on a non-dried screed, but for a semi-dry option this is possible after 6-10 hours or the next day with a light step for a person weighing up to 100 kg. But it is still advisable not to do this on the first day, and if there is a need, then before walking, attach wide boards-pads to the shoes, like snowshoes;
  • Grinder or hand floats for polishing the hardened screed.

Ideal conditions

The following characteristics of the ideal setting for drying a semi-dry screed are present:

  1. Additional moistening in the first 7-10 days. Moreover, this should not be pouring, but rather spraying a small amount of water.
  2. Preventing natural moisture removal (evaporation) by covering with film or similar material on the 3-4th day after backfilling, the material overlap at the edges should be 30-40 cm.
  3. Humidity in the room is about 60-65% (ideally 70%).
  4. Temperature is about +20° C. Higher or lower values ​​are allowed (for example, in the south in summer it can reach +25 or more, in the northern regions it can be close to +5). But in any case, the value should not be lower than +5, otherwise the process of gaining hardness will be stopped, the final material will be loose, as it will freeze. If the temperature is excessively high, then you will need to provide more abundant humidification and ensure high air humidity. That is, these problems can be solved by corrective measures.
  5. It is necessary to ensure that the room is as hermetically sealed as possible, if possible, so that a special humid microclimate is created in it. However, if this is not possible, then a high-quality polyethylene cover solves the problem.
  6. There should be no drafts, changes or jumps in environmental parameters. Stable conditions are a guarantee of uniform, high-quality hardening.
  7. No moisture-absorbing materials in the room (fabrics, wood, plaster, etc.) and releasing chemical components (oils, petroleum products, acids) substances. Evaporation of pure moisture is acceptable and even desirable.

It would be more accurate to refer to the screed preparation process as hardening in a wet state rather than drying. Naturally, at this point the material dries, but this process shouldn’t be finished before the material reaches a certain hardness level. Accelerating it will cause the base to collapse.

How to properly care after pouring?

Upkeep and attention to detail Once it’s poured, leave it semi-dry until it hardens completely, and then:

  • Immediately after backfilling, cover with plastic film, with an overlap of material (extending beyond the edges) of 30-40 cm, it is advisable to press the ends to minimize the gaps and the penetration of air inside, which accelerates the removal of moisture from the solution.
  • Moisten by spraying after 3-4 days, cover again. This is especially true if the heating is on in the room, which is recommended to be turned off during this period, of course, if maintaining the temperature is not required.
  • Optimum temperature +20 … +24 ° C. Other values ​​​​are allowed, but it should be taken into account that the curing time may change slightly. If the value is below +5 ° C, then it is necessary to increase it with heaters, heating. In this case, heat flows should not be directed to the solution, they are directed towards the ceiling (devices are turned around, protective sheets are installed). If the air dries out, it is recommended to put a container of water in the room. Forced hardening and drying cannot. Artificial drying is possible only after finally hardening, when the humidity in the solution is constantly held (due to wet climate, soils) and does not fit the norms for a certain type of flooring;
  • If air humidity is below 60%, then it can be increased by placing dishes with water in the room or periodically make moisturizers from sprayers. And you can also make the humidification of the solution itself more intensive.

During the two weeks that the screed is hardening, it is especially important to stay away from drafts and sudden changes in temperature and humidity.

Drying time and operating instructions

After the first three to four days, the laid solution needs to be moistened because it should not dry out too quickly.

After two to three days, if the facility has a high temperature and low air humidity. Throughout the day, the surface needs to be sprayed multiple times.

Remind yourself that the solution should harden wet and stay that way for as long as possible during the slow maturation process, and that a semi-dry mixture contains less water. For the same reason, the mixture needs to be covered with film to allow for as much time as possible for the moisture to evaporate.

Without any assistance, the screed covered in polyethylene should dry after a week, or eight to ten days in an extremely humid environment.

Since humidity is the foundation of quality, it is crucial to provide it. It is best to do so for eight to ten days during the first week. The mixture will gain 70% of its hardness during this time at roughly +20° C, and the cement will reach a maximum strength of 90% in just one month.

Furthermore, because of the peculiarities of the hydration processes, the solution will continue to draw moisture from the environment and from itself for a considerable amount of time after the final floor covering is laid.

One benefit of a semi-dry screed is that, six to ten hours after the solution is poured, you can walk on it, albeit cautiously (with a light step), ideally with special wide pads on your shoes.

After this time, a person of average build can already be supported by the material, and an additional load of up to 100 kg is also feasible. Some experts advise delaying for at least 12 to 18 hours, though. After four to six days, the composition can be subjected to more intense influences.

For the first ten days, you are not allowed to load the surface with more than 100 pounds. While finishing work can be completed, it is not advised to place scaffolding or stepladders on the screed during the designated time. Heating is not an option unless it is absolutely necessary to keep the temperature above +5. In any event, because of its proximity to the base, you are unable to maintain the microclimate by turning on the heated floor for 30 days.

Semi-dry screed curing times on average:

  1. 35 mm thick from 7 to 10-13 days;
  2. for a layer of 40-50 mm – a little more than 2 weeks.;
  3. for 70-80 cm – 3 weeks.;
  4. 100 mm and more – 4 weeks.

Since our curing time is significantly shorter than that of a traditional wet base, it also contributes to the benefit of requiring more meticulous care.

Checking the humidity level

Using a paper napkin placed on the surface and pressed down with a hard object of the same shape (like a tile) is a common method of determining whether the screed is dry. If the product is still dry after a day, you can begin installing the floor covering.

Specialized instruments for humidity measurement

  • Carbide hygrometer, similar complex laboratory equipment. Gives extreme accuracy, indicators in cm%, analyzes within the thickness of the material. But these are not very practical devices; they are mainly available only to companies that are constantly engaged in such work. Devices violate the integrity of the mixture (you need to stick probes), expensive. Buying them for rare, single use is not particularly advisable.
  • Electronic moisture meters. Indicators are not in CM, but in %. As a rule, it is precisely such devices that are used to analyze screeds in everyday life, since they are simple in themselves and in use, not too expensive, and do not violate the integrity of the object. They analyze only the surface, the accuracy is somewhat less, but for the vast majority of work in private construction they are more than suitable.
  • Conductometric devices not used, since they cannot measure humidity below 5%.

If there is a warm floor, the device readings for the finished screed shouldn’t be higher than CM 2% and CM 1.8%. However, because of their complexity and high cost, carbide hygrometers and other similar sophisticated laboratory equipment are not used as often as they could be. These indicators are in CM%.

We continue to use this measurement scale because these indicators are included in GOSTs and other standards, and we must translate them into the values displayed by common, household moisture meters.

Official standards indicate humidity standards in "CM%," which are units of expensive, sophisticated laboratory techniques that are not applied in real-world settings. The dielectric method and household moisture meters with alternative measurement units are employed more frequently.

Therefore, we make a translation: 2CM% correspond to 3.4%, in the same proportion we relate the remaining standards. That is, the maximum for the readiness of a semi-dry screed according to a household moisture meter, which should not be exceeded, is 3.4%, and in the standards of some CIS countries this figure is 4%.
Compliance with the standards for the humidity of the solution is important primarily for the subsequent floor covering, since if the value is violated, it will absorb moisture, deform, the glue will not harden, adhesion will decrease, mold and fungus will appear. In this regard, stone materials are more resistant, therefore the moisture level figure in the base under them is higher.

What to do if it does not harden?

For instance, the thickness of the layer is 8 cm; measurements were made using a dielectric apparatus, meaning that only the surface was examined; the results show that the layer thickness is 3.3-2.4%, or 2% of CM. Everything appears to be OK at first, but the figure within the solution’s thickness can be as high as 5.7%—6.3%, which is unacceptable.

You can wait longer and dry the material separately if the abnormal humidity on the surface persists, especially in the thickness of the screed. However, this won’t always help, as the humidity of the soil or climate is typically the cause of such a phenomenon.

It is more prudent to use epoxy special primers (TDE GPIEP-2K, Uzin PE 480) to create a vapor barrier, preferably in two layers. These products prevent the growth of fungus and block any remaining moisture.

Actions after final drying

Using specialized graters and devices, the solution is sanded following its final hardening.

Screws are sealed with a pre-made solution as soon as beacon holes and recesses are poured, and then regular maintenance is performed, such as wetting and sanding. Special mixtures are used to level cracks and gaps that appear after the screed matures, but we only pay particular attention after the final hardening.

The heated floor and artificial drying can only be used once the maximum curing period of four weeks has passed.

Rules for Caring for a Semi-Dry Floor Screed Details
Drying Time A semi-dry floor screed typically takes about 7 days to dry enough for light foot traffic and up to 28 days to fully cure.
Humidity Check To check humidity, place a plastic sheet on the screed for 24 hours. If no condensation forms underneath, it"s dry.
Watering the Screed Lightly mist the surface with water for the first 3 days to help it cure properly.
Room Ventilation Ensure good ventilation in the room to speed up the drying process, but avoid strong drafts that can cause cracking.
Avoid Heavy Loads Avoid placing heavy loads on the screed during the curing period to prevent damage.

Maintaining a semi-dry floor screed is essential to achieving a long-lasting, superior finish. You can create a smooth, level surface that will endure over time by following the correct procedures. To ensure proper hardening and avoid cracks, keep the screed moist during the initial curing period. It can be kept at the proper moisture levels by covering it with plastic sheeting or giving it frequent water sprays.

A semi-dry floor screed usually takes seven to ten days to dry, depending on thickness and surrounding factors. It is imperative that enough time be given for the screed to fully dry before starting any additional building or flooring installation. Hastily completing this procedure may result in problems such as incorrect bonding and possible harm to the screed.

A straightforward plastic sheet test or the use of a hygrometer can be used to determine the screed’s humidity levels. After putting a plastic sheet on the screed, wait a day. Condensation under the sheet indicates that the screed is still too wet and requires additional drying time. You can use this quick test to help you decide when it’s appropriate to move forward with the next stages of your project.

You can guarantee a solid and stable foundation for your flooring by taking good care of a semi-dry floor screed and seeing to its drying process. The best outcomes require careful monitoring and patience. In addition to extending the life of your floor, properly cured screed also improves the general standard and security of your building project.

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Andrey Ivanov

Experienced civil engineer with more than 20 years of experience. Specializing in the construction of industrial and civil facilities. Author of many publications in professional journals.

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