Content
- What factors influence the drying time of the screed?
- Calculation of the time of complete drying
- Temperature and humidity conditions during screed drying
- The effect of waterproofing on drying time
- How to determine if the screed is dry?
- What will happen if you do not dry the screed?
The organization of repairs in the apartment should ensure not only the high quality of the work, but also the rational use of time. Warming and leveling the floor using concrete screed - the process is not only laborious, but also quite lengthy. You need to know how much the concrete screed dries in order to meet the required time interval, for example, on vacation or in the warm season. The rush during this operation can lead to sad consequences: the finish coating, laid on an dry base, can become distorted from moisture, which will lead to repeated repairs.
What factors influence the drying time of the screed?
First of all, it is necessary to draw a line between the time of setting the cement screed and the time of its complete drying. After the solution has set, you can walk freely on the floor. Full drying of the rough floor is a longer process and can last for a month or more. Only after its completion can you finish the floor or bring furniture. For this period, you can safely plan other things or just relax.
Tip: Do a screed at the very beginning of the repair! You can walk on it in a week, but for now to go completely dry, you will be able to level the walls, prepare for the finish and by the way. Thus, by gluing the wallpaper and laying the flooring, the screed will already be completely dry.
The full 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;
- quality waterproofing base.
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Calculation of the time of complete drying
The formula used in calculating the time required to completely dry the solution takes into account the thickness of the screed up to 40 mm. If the thickness is greater, then the drying time of each additional centimeter of the solution layer is added. The duration of these intervals depends on the materials used.
For gypsum-based screeds, the total drying time is calculated as follows: with a thickness of up to 40 mm, it takes 42 hours to solidify each centimeter of the layer. Therefore, 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 every extra centimeter will require an additional 90 hours to dry.
For example, a gypsum-based rough coating 60 mm thick will completely dry after 348 hours (168 + 90 + 90), that is, after almost 15 days.
Cement-based screeds take much longer to dry:
- With a thickness of up to 40 mm, every centimeter of cement screed must dry for a week.
- It takes another two weeks to dry each additional centimeter of cement subfloor.
So, for complete drying of the cement-based screed 80 mm thick it will take 12 weeks (4 + 2 + 2 + 2 + 2).
The gypsum screed dries relatively quickly. But you should not forget that gypsum is afraid of water. Therefore, gypsum-based solutions should be used in dry rooms. For bathrooms and toilets, cement mortar must be used.
Temperature and humidity conditions during screed drying
In order for the 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% air humidity at a temperature of 20–25 C.
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Excessive moisture will increase the drying time. And with insufficient humidity, there is a high risk that the surface will become cracked due to too rapid evaporation of water.
Insufficient humidity in the room can be compensated by covering the surface of the screed with plastic wrap. AT SNiP 3.04.01-87 clause 4.8. It is recommended to cover the screed with a layer of constantly moist water-retaining material for 7-10 days. In the updated version of the rulebook SP 71.13330.2017 clause 8.1.12 indicates a period of at least 7 days.
Low temperature in the room will slow down the drying process, but it is not worth it to speed it up by heating the air; at high temperature, the screed will crack and peel off. If the work is carried out in an unheated room, then it is impossible to prevent freezing of the rough coating using thermal insulation materials.
It is necessary to fill the cement screed in the room without heating one and a half to two months before the onset of frost, otherwise the dry base will collapse. The use of special plasticizers allows you to make the solution resistant to freezing temperatures, but it will significantly increase the cost of repairs.
Drying solution must be protected from direct sunlight and drafts. Of course, they will accelerate the drying, but for chemical processes that occur during the solidification of the solution, uniformity is more important than speed. Therefore, it is better to exclude the interference of these factors and get a quality result.
The effect of waterproofing on drying time
Even under a rough screed must be waterproofing. It is better to perform it using rolled materials or to cover the surface with bituminous mastic. At the same time, one must not forget that waterproofing should capture walls to a height of 15–20 cm. In the absence of waterproofing or its low quality, moisture will fall into 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 thoroughly as possible. This is especially true for apartments on the ground floors located above moist or often flooded basements.
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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 dry base can lead to damage to an expensive laminate or other coating, and hardly anyone will want to start anew the epic of floor repair. 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 the napkin is wet after 24 hours, then the solution has not dried out to the end, and it is necessary to wait again. If the napkin is completely dry, the screed has dried.
In addition to the method with a napkin, you can use special devices, 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 flooring and the presence of floor heating.
Official requirements SNiP 3.04.01-87 Insulating and finishing coatings paragraph 4.42, table 24 weight humidity not more than 4%.
What will happen if you do not dry the screed?
The base can "lead", mold and fungus will appear under the topcoat. In the case of laying tile, peeling of glue is possible, and it can also “tear” tiles. It is also possible to detach the screed from the base.
After the screed has completely dried, 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.
