The maturity of screed

Screed is the usual floor that is made and then covered with floor coverings. Cement screed, ie wet screed mortar, is still the most widely used screed. From this it can already be deduced that the screed floor first has to harden and above all to dry before being coated. This is called the maturity. Everything you should know about the screed readiness of Estrich has been summarized below.

Cement screed - the most used floor today

To be able to occupy a floor further, a uniform and level floor is first produced. In the past, depending on the structure and floor, the procedure was as follows:

  • Stone or tiled floor with low bed
  • stored wooden floor

With the reinforced concrete ceiling, construction has changed significantly. It is difficult to lay tiles or even a carpet on the raw ceiling or the raw concrete floor. In addition, underfloor heating is standard today. To evenly adjust the surface and also to install a floor heating, a fine concrete floor is built on the coarse concrete floor - the screed floor.

Screed must set and dry

Often cement screed is used for this. In principle, this cement floor must then follow the same physical rules as any concrete: the cement must set, harden and dry. Detailed information can be found here for curing concrete.

If this is not followed, consequential damage is almost inevitable. Especially with later floor coverings, which virtually seal the screed, building defects can be expected very quickly. Incidentally, that's why the mighty Hoover dam in the US was not cast from a concrete part, but made from many small concrete blocks. The concrete would harden and set today.

Minimum hardening times of cement screed

If the screed can then be occupied, he has reached his Belegreife. In DIN 18560 you can read the minimum hardening times. However, these do not necessarily correlate with the maturity of the document. The drying of the screed depends on various factors such as temperature (in the building as well as the ambient temperature), humidity, thickness of the screed covering, etc. Consequently, the ventilation or dehumidification of the room air is an essential aspect.

Ready for laying from the floor screed

With a covering thickness of 45 to 50 mm under optimal conditions at least four weeks can be estimated. However, this is to be understood as the lower limit. Also, no mistakes should be made when ventilating the screed. In detail you can read here what has to be considered when ventilating cement screed.

Take into account the humidity of the outside air

Also note the equilibrium moisture content when the screed has dried out. Often now the mistake is made that the windows are opened long and long, so that the humid outside air can penetrate. The screed, however, like other materials, strives to produce its moisture content adapted to the environment. You can think of it as a dry wood, exposing it to great moisture. The moisture content will adjust. So also with screed.

Measuring the residual moisture to reach the screed maturity

The floor leveler must check the moisture content of the screed floor after the drying and curing time. For this purpose, different methods in question, which is usually resorting to the so-called CM method, since this is also legally usable. In addition, the Darr method and electrical resistance measurement are also possible as a test method. According to the CM method, the moisture content of the screed must not exceed the following values ​​depending on the intended floor covering:

  • 2% for stone and ceramic coverings in a thin bed
  • 2% for parquet and laminate
  • 2% for resilient floor coverings (linoleum, rubbery etc.)
  • 3% for stone and ceramic coverings in the thick bed
  • 2.5% for carpets and other textile coverings, steam retardant
  • 3% for carpets and other textile coverings, open to diffusion

If an underfloor heating system is installed (heated screed), even more stringent guideline values ​​apply for residual moisture, in which the screed is ready for laying.

Tips & Tricks

Use the articles in the house journal, which we offer for drying and ventilating screed floors. They should plan the time that screed needs to reach maturity rather generous than too short. If the maturity date has not been reached, construction damages can be extensive and costly.

Product Image: Dagmara_K / Shutterstock

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