The organization of repairs in the apartment should ensure not only the high quality of the work carried out, but also the rational use of time. Warming and floor leveling with concrete screed - the process is not only laborious, but also quite lengthy. You need to know how long the concrete screed dries in order to meet the required time interval, for example, on vacation or during the warm season. Haste in performing this operation can lead to sad consequences: a finished coating laid on a wet base can warp from moisture, which will lead to repeated repairs.
What factors affect the drying time of the screed?
First of all, it is necessary to draw a line between the setting time of the cement screed and the period of its complete drying. After the mortar has set, you can walk freely on the floor. Complete drying of the subfloor is a longer process and can take a month or more. Only after its completion can you lay a fine floor covering or bring in furniture. During this period, you can safely plan other things or just relax.
Tip: Make a screed at the very beginning of the repair! It will be possible to walk on it in a week, but for now it will be completely dry, you will be able to level the walls, prepare for finishing and other things. Thus, by the time of wallpapering and laying the flooring, the screed will already be completely dry.
The complete drying time of the cement subfloor depends on the following factors:
- screed thickness and the number of layers in it;
- materials used for pouring;
- humidity and temperature indicators of the room;
- base waterproofing quality.
Calculation of complete drying time
The formula used in calculating the time required for the complete drying of the solution takes into account the thickness of the screed up to 40 mm. If the thickness is greater, then the time is added to dry each additional centimeter of the solution layer. The duration of these intervals depends on the materials used.
For gypsum-based screeds, the complete drying time is calculated as follows: with a thickness of up to 40 mm, it will take 42 hours for each centimeter of the layer to harden. This means that the time intervals for layers of different thicknesses will be as follows:
- up to 1 cm - 42 hours;
- up to 2 cm - 84 hours;
- up to 3 cm - 126 hours;
- up to 4 cm - 168 hours or 7 days.
If the total thickness is more than 40 mm, then each extra centimeter will require an additional 90 hours to dry.
For example, a gypsum-based rough coating with a thickness of 60 mm will dry completely after 348 hours (168 + 90 + 90), that is, after almost 15 days.
Cement-based screeds dry much longer:
- With a thickness of up to 40 mm, each centimeter of the cement floor screed should dry for a week.
- It will take another two weeks for each additional centimeter of cement subfloor to dry.
So, for complete drying of a cement-based screed with a thickness of 80 mm, it will take 12 weeks (4 + 2 + 2 + 2 + 2).
Gypsum screed dries relatively quickly. But at the same time, one should not forget that gypsum is afraid of water. Therefore, gypsum-based solutions should be used in dry rooms. For bathrooms and toilets you need to use cement mortar.
Temperature and humidity conditions when the screed dries
In order for the floor screed to dry within the calculated time interval, it is necessary to comply with the requirements for the microclimate of the premises. Ideally, this is 60-70% humidity at a temperature of 20-25 C.
Excessive moisture will increase the drying time. And with insufficient moisture, there is a high risk that the surface will become covered with cracks due to too rapid evaporation of water.
Insufficient air humidity in the room can be compensated by covering the surface of the screed with plastic wrap. VSNiP 3.04.01-87 clause 4.8. it is recommended to cover the screed with a layer of constantly wet water-retaining material for 7-10 days. In the updated version of the set of rulesSP 71.13330.2017 clause 8.1.12 specifies a period of at least 7 days.
Low room temperature will slow down the drying process, but it is not worth speeding it up by heating the air; at high temperatures, the screed will crack and peel off. If work is carried out in an unheated room, then freezing of the rough coating should not be allowed using heat-insulating materials.
It is necessary to pour a cement screed in a room without heating one and a half to two months before the onset of frost, otherwise the wet base will collapse. The use of special plasticizers makes it possible to make the solution resistant to negative temperatures, but will significantly increase the cost of repair work.
The drying solution must be protected from direct sunlight and drafts. They, of course, will speed up drying, but for the chemical processes that occur when the solution hardens, uniformity is more important than speed. Therefore, it is better to exclude the interference of these factors and obtain a qualitative result.
Effect of waterproofing on drying time
Even under the rough screed must be waterproofing. It is better to perform it using roll materials or cover the surface with bituminous mastic. At the same time, we must not forget that the waterproofing should capture the walls to a height of 15–20 cm. In the absence of waterproofing or its poor quality, moisture will enter the screed, which will increase its drying time. It can also lead to further destruction of the floor, so it is better to carry out waterproofing work as carefully as possible. This is especially true for apartments on the first floors, located above damp or often flooded basements.
How to determine if the screed is dry?
How to find out if the solution has completely dried out and is it possible to proceed with the installation of the floor covering? The question is very important, because a wet base can lead to damage to an expensive laminate or other coating, and hardly anyone wants to start the epic of floor repair again. There are several ways.
The most affordable and easiest way: a paper napkin is placed on the surface of the screed, covered with a piece of polyethylene and left for a day. If after 24 hours the napkin is damp, then the solution has not yet dried out completely, and you need to wait more. If the napkin is completely dry, the screed is dry.
In addition to the napkin method, special devices can be used, for example, a carbide hygrometer or an electronic moisture meter. But it makes sense to purchase such a device only for large-scale construction, which implies its regular use.
The most accurate measurements of screed moisture are made using a carbide hygrometer.
The range of permissible residual humidity is 1.5–3%, depending on the nature of the floor covering and the presence of underfloor heating.
official requirementsSNiP 3.04.01-87 Insulating and finishing coatings item 4.42, table 24 weight moisture not more than 4%.
What happens if you do not dry the screed?
The base can “lead”, mold and fungus will appear under the finish coat. In the case of laying tiles, adhesive peeling is possible, and it can also “tear” the tile. It is also possible to detach the screed from the base.
After the final drying of the screed, it is checked for integrity visually and by tapping with a hammer. Only after making sure of the proper quality of the base, you can proceed to laying the flooring.
