Today I went to test the humidity in the house again.

The results are:

Place Humidity (%)
Cellar
Utility 18.8
Basement 1 19.8
Basement 2 17.7
Laundry 18.5
Ground floor
Guest 19.3
Living 14.5
Dining 15.9
Kitchen 15.8
Shower 15.1
Storage 16.1
Hallway 17.4
First floor
Child 24.4
Storage 21.7
Bathroom 19.4
Bedroom 19.1
Study 20.6
Landing 21.1

So, by all accounts, the screed seems to be dry enough.

HTH,