Anhydrite screed - laying vinyl at 50-70 millimeters thickness?

There is empirical data, and it is reflected in the DIN standard.
Anhydrite screed as a heated screed can be laid with 0.3 or 0.5% residual moisture according to a CM measurement.
By the way, this is also stated in the instructions for your flooring, or the manufacturer refers to the BEB leaflet "Assessment and Preparation of Substrates, Installation of Elastic and Textile Coverings."
Digital measuring devices are only suitable for preparing a CM measurement.
Hopefully, will see the post and write something about it.

With a bit of luck, @KlaRa will see the post and write something about it.

(... he already sees it ....)
Absolutely correct, what "T_im_Norden" wrote about it!
If a CaF as heated screed is not dry after several weeks, the fault lies elsewhere, but not with the screed!
However, if I take the measured relative indoor humidity of 15%, well, then I ask myself, what value must still be reached to realize that it can’t get any drier??
Screeds release their mixing water into the indoor air.
And if the indoor air is dry, it is not far-fetched to suspect that it depends on the building components which no longer release moisture into the indoor air (can).
And whether we lay a "full PVC" (the term does not exist) or a synthetic rubber covering on too moist a substrate: it will sooner rather than later form bubbles in the covering layer. The thickness or composition of an elastic covering therefore has no influence on whether a covering stays put or lifts up due to too high residual moisture in the substrate!
If measuring points in the heated screed are specified, a CM residual moisture measurement must be carried out promptly before installation.
If no measuring points are present, it gets interesting. Because the installer raises his concerns and the client has to decide whether to take the risk.
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Waiting eagerly for the future results:
KlaRa

Hi ,

so a measurement of the wooden walls also showed that they are very dry and partly below 15 digits.

The strange thing is, under the stairs for example, where we couldn’t sand, no sunlight gets in, no drafts etc., we have 40 digits... so much for that. In the hallway, directly adjacent to the living room, partly only 30 digits... someone has to explain that to me, and in the living room where sunlight constantly comes in, drafts occur during shock ventilation etc., we hover around 50 - 70 digits...

Yesterday I performed a foil test; in the living room area where we had about 50-60 digits, there was no moisture under the foil (1 sqm glued for 24 hours).

With the foil in the front area where we have about 70 digits, about 4 small water droplets were visible...

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Thanks for your opinion, but I’m not any wiser now, a CM measurement can no longer be done since it has already been plastered (see picture).

And as mentioned, the room air is very dry, so I don’t understand why the screed still has such values and why they don’t finally go away... my heating program has been running continuously since about February 24th (fear of electricity bill :eek: - LWZ 5S Plus from Stiebel Eltron). Since then, we have had a constant room temperature of about 29 degrees since the end of February.

What do you personally expect now in this situation I described? Should I expect something now (something molding?, will the floor discolor, or what else)?

Sorry, I’m a layman and have my concerns...

and I basically just want to know if I can sleep peacefully the next few nights and not have to think that, to put it bluntly, in 3 months I have damage here in the living room and in the worst case the floor has to be taken out.

Thanks again!

@ "Arzok90": Can you tell us from which "digit size" something is moist, no longer so moist, dry, or completely wet? No, there are no exact values that can be used. The "digits" only indicate abnormalities to me in an object. And if 70 digits are displayed in a corner of a room, that would be a reason for me to open up and take a look. With sufficient probability, I would then recognize that the screed thickness here is greater than in the other areas (with lower values). The foil test was already a good testing method! Do it again in the middle of the room. Place a hygrometer under the foil, which is sealed at the edges with tape (stuck to the screed). Well, there are no generally accepted limit values with this method either, but if you are around 70% RH, everything should be "in the green zone." Before this test, however, do the following: Turn off the heating! Wait until the screed surface has cooled down, open windows widely for a long time and ventilate thoroughly. Wait 3 days, heat the heating up again immediately to "full power" and keep it for 2 days. Cool down again and allow to lay at room temperature. PS: who says that you cannot do a CM residual moisture measurement if it has already been skimmed??? Everything is possible! ------------------- Good opportunity: KlaRa

We suspected a phase break during our drying process according to the site management. Superficially, nothing was detectable anymore (foil test), but the CM measurement was off. Only patience and a procedure as described by Klara helped. Ultimately, due to time pressure, we had the flooring installed with a slightly too high measurement value. The tiler used a special adhesive that was approved for this. The parquet layer sealed the screed. So far, everything has gone well.