ᐅ What level of residual moisture can the tile installer start working with?

Hello everyone.
Our screed still has a residual moisture content of 2.6% CM. Exactly 7 days ago, it was 2.7% CM.

Two dehumidifiers are running continuously... Why is the screed drying so slowly in our case?

From what % CM can the tiler start their work?

The question is what type of screed is used. I mean 3% moisture for cement screed and about 2% for calcium sulfate screed. Between 1.6% and 2% for laminate/wood flooring/vinyl.

It is cement screed.

Is the underfloor heating already running, or just the construction dryers?

The screed heating program has already run twice...

It is supposedly only supposed to run for 8 days (Viessmann gas heating).

2.0% for cement screed and tiles, 1.8% for parquet flooring.
For tiles, there is a special adhesive that also works with higher moisture values.
For parquet, you can apply a primer beforehand, but that stuff is expensive.

8 days sounds more like functional heating rather than drying.
Maybe the drying time (capillary break) is a bit overestimated.

What temperature and humidity levels do you have?