pim1985
2023-01-06 09:36:09
- #1
Hello " ".
In this case, the answer is not simple.
Objectively viewed, the current state of the art is as "i_b_n_a_n" described it. According to the rules of the floor layers, this describes a CM residual moisture value of 0.5 CM-% listed in the current DIN 18365 for underfloor heating and calcium sulfate screeds.
However, this is contradicted by the opinion of the parquet layers (as well as professional associations). There are actually currently two groups in dispute, whereby "the power" apparently is shaped by the lobbyists of the industry who are involved in the DIN committees.
In fact, the value of 0.5 CM-% has represented the state of the art for years in Switzerland (allegedly without damage).
Back in Germany, the "fear" of parquet layers to be held liable for moisture damage is quite understandable to me personally.
Moreover, the sample extraction from the screed cross-section is supposed to be taken only from the upper third by the floor layers; parquet layers prefer to take their sample, with which they determine the residual moisture content, over the entire cross-section.
So it is not easy to clearly answer your question according to technical regulations.
And the DIN?
Well, it is assumed that a DIN correctly describes the current state of the art at the time of publication.
However, if you are professionally involved with construction defects and regulations, this is a misconception.
Also, the hint in one of the subsequent posts to your question, "pim1985", namely to apply a moisture barrier based on synthetic resin, is a recommended procedure that I can only warn against!
This solution, which in practice works with cement screeds depending on the manufacturer, or not, must never be used with calcium sulfate screeds!! Entrapped moisture, whether as excessive residual moisture or penetrating moisture, is "fatal" for the moisture-sensitive calcium sulfate screed. Because excessive, and thus entrapped moisture leads to decalcification. Result: the screed becomes at least soft at the boundary of the barrier.
So what to do in the described situation?
On one side, there is the pressure from the builder to move in, on the other side, the understandable fear of parquet damage by the parquet layer. I personally would take three samples over the entire screed cross-section at different sampling points, immediately store them in double and sealable PE bags, and dry them as quickly as possible by the gravimetric method at 45°C until weight constancy is reached.
This method is admittedly not common in the trade. But it is used by experts in floor technology when more definite results are required.
Since both methods, the gravimetric and the CM method, produce values with different units (namely mass-% and CM-%), the procedural difference in size up to 0.5 is almost ZERO, a result < 0.5 can be accepted as ready for installation when sampling over the entire cross-section. Because the gravimetric method in the drying cabinet delivers slightly higher (correct) values and there is a safety margin.
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I further suggest that you print out this article and hand it over to the site manager, who is quite correct in his view, and to the parquet layer, who also holds an understandable, though contrary opinion.
Because ultimately, it is not important who held which opinion when, but it is important that no moisture-related floor damage occurs later!!
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Good luck: KlaRa
Thank you very much for this answer!
We are now at 0.40 CM-% and when the painters are gone, we will set up drying devices. Ultimately, we want to play it safe and take no risks. We hope that this way we can reach 0.30 CM-% even faster.